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Information on Levels of Environmental Noise Requisite to Protect
Public Health and Welfare With an Adequate Margin of Safety
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Environmental· PJ;ote.ction Agency
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INFORMATION ON LEVELS OF
ENVIRONMENTAL NOISE
REQUISITE TO PROTEC.T
PUBtiC HEALT.H AND .. WELFARE . -:;. . . .... •::_ . . -.-.. • •;".
WIT.H AN ADEQUATE MARGIN
()F SAFETY'
. . . . -;--,' ..
. M:ARCH 1974
.. ·.·-
.-:·''·_-_·., < :.. • ........
r!IE '{is. ENVIRONMENTAL PROTECTION AGENCY
. OFFICE OF NOISE ABATEl'\'IENT AND CONTROL ..
·-·; .
. .. : :, .. :This: do~~~:;h; .:been appr~~e'f for general
. . availability. lt. does not constitute a standard,
· specification, or· regulation.
---'--······----------------
-IIJ'IilOi:iiDiY _____ _
NATIONAL TECHNICAL
INFORMATION SERVICE ·
. '-------U.S. D£PAifMEJtf OF COMM£Rct
SPtiiiGfiELD. VA. Z%161
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550/9-7 4-004
PB-239 429
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4. Tit '_e z.n:::l ~~ou::ie
..
SSu/9-74-004
Information on Levels of Environmental Noise Requisite to
Protect Pt:blic Healt:::. anC. ~velfare with an Adequ.ate Hargin of
Safety
5. Report D.:ue
!.~arch 1974
,~.. . .
i. Aurbor(s)
9. Periorming Or;·,anization ::-.:1e and Address
Environmental Protec·t.ion Agency~
Office of Noise Abatement and Control
. 1921 Jefferson Davis Highway 1 Crystal Mall #.2
Arlington, Virginict _ .20450
1 2. Sponsoring Organization Nar.~e and A<idress
.Environmental Protection Agency
Office of·Noise.Abatement and Control
1921 Jefi'erson Davis Highway 1 Crystal Mall.);!2
Arlington,. Virginia 20460.
l6~ Abstra.cts
'a. Performir.g Orgaciz:uion R'!?C.
No.
· 10~ Project/Task/Work: Unit !'lo. I·
11. Cont.tact/Gran~ No •. ·
IJ. Type of Report & Pe.rioo
Cove.red
Final
14. I
Thi~. d~ctunE;nt id.e~ti.fi~s noise. lev~is. consl~t~nt with the· protection ot' :EJublic h~~i th
and welfare against· 'he~ring loss, annoyapce,. and activ:ity interference.·
·f
-· ..:.. ....
17. Key '~'ords and Doc:um.em Analysis. 17a. Desc:i.ptors·
noise levels, hearing, activity interference, an."loyance, maximum. exposure,. equivalent
sound level (Leq>, Ldnt·impul~e noise1 acousti7. energy
··-··. ,._ .... ·--:-.
-. . . •'. ~ ..
~ _ .... ·.-
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17b. Identifieis/Opt>l1~Ended T~~m~ . -.. . ··. , . ,_._;. -:··;_ ........ _ ... -:.; ..
· .... _ ... -.
ric:.: cosA tl Fic.ld/Gcoup ·.·· . . . . . . .
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U:-.iCT .~. '"-'" F.n
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Unlimited
:o.. 5ecu:i:y. Class fThiS
Po1ge
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FOREWORD
The Congress included among the requirements of the Noise Control Act of 1972 a
directive that the Administrator of the Environmental Protection Agency" ... develop and
publish criteria with respect to noise •.. " and then "publish information on the levels of
environmental noise the attainment and maintenance of which in defmed areas under vari-
ous conditions are requisite to protect the public health and welfare with an adequate mar-
gin of safety."
Not alfofthe scientific work_ tll,~qnequired for bfisiilg such levels of envir~n1llental
· noise on preCise objective, factors has-been completed. Some investigations are currently ·
underway, and the need for others has been identified. These involve both special studies
on various aspects of effects of noise on humans and the_ accumulation. of addi tiona! _ .
: .. epidemiological data:;I.n soine cases, a. considerabl~ period of time musfelapse bef~r.e the-.-
results will be meaningfui, due-to:the-long-term nature of-the investigations involved;· Non~-
_ the less, the~~ is information available . .from which extrapolations are possible and. about ·
-which reasoned judgments can be made.
. . . .
Given the foregoing, EPA llas sought to provide information on the levels of noise
.. requisite to protect.public health and_welfare with an-adequate margin, of safety. The infor, -
mation presented is based: on analyses;e~t~apolatiorts and evalu-ations of the presentstate -·
of scientific knowledge. This-approach is not unusual or. different from that. used for other
environmental stressors. and pollutants. As pointed out in "Air Quality Criteria:• ...,-Staff
Report, Subcommittee on Air and WateJ: Pollution, Committee on Public Works, U.S.
Senate, July/:1968; ·:-' . · :· · · ---· · --· -· ·. -· . ·
··.··
The protection of pub-lic.health is requrred·.action based upon best-.
evidence of cau5ation available~ This pltilesophy was appro.priately
expressed by Sir E. B. Hill, 1962, when·he wrote; ~All scientific
work is iilcomplete-whether it be observational or experimental.
All scientific work is liable to-be upset or modified by advancing
knowledge. That does not confer_ upon us freedom to lower the . • .. _ ..
knowledge we. already have, or to postpone the action that it appears
to demand: at a given time. The lessons of the past in general health and safety practices are easy. to tead. They. are characterized by em~ .
pirical decisions, by eternally persistent reappraisal of-public health
standards against available knowledge of causation, by consistently
giVing the public the beL-.:fit of the doubt, and by ever striving for
improved enVironmental-quality-with the accompanying reduction
in disease morbidity and mortality. The day of precise quantitative
Foreword
.. ··:;.
• ...• ······
.......
'"":,.-.. ··
measurement-of health and welfa,re effects has not yet arrived. Until
. · · · .. · ···· .. such measure,ment is possible~action· must be based upon limited . . .: : ..
,, : .. knowhidge,:g'\lided by the~principal()f the;: ¢rihancement ofthe.qiiauw·:·; . ,. ;·
· of human life. Such action is based •on a philosophy ·ofpreventiv:e: · · ·. ··· ·. ·
·triedicirie·;'·'"···,. ... ,·.:, . ... · · ··;:.,, •. _ .. , .. ::;:··· .
. ~ ..... ...... · .. •:··•· .· ... '. .. . .:.:': .: :.
. . ... The foregoing repre~ts the approach t3ic~n by EPA in the prepar~tion of'ihls.present
doc~ent ori noise: As the fund of'.knowledge is expanded, improved and reffue.d. reVisioJ:lS ·
of thi~~docu.merit will occur~ · · · . . . :.~ ' .:···· · · · · ..
:. ·•. . ........ ·'·,: \.:•.
The incorporatio~ of a margiri of safety in· the identifi~ation ofnon-haiil:rde>uslevels:
.. · ·· ... · iS::not new. In·· most cases, a st~tistical'detemuilation iS made ofthe loweSt levei:~t;which .
haz1nfu1 effects could occtir, and then:~· a¥itional.cotrection 1s .applied as·.a .• iilargiji .• ~f ·
. ·: ... ·. . · .. ·.· , .... ~ety .ln.. ~.lle: case of-noise.;the: margin·of_~~ty. ha~-~11.: ~y~lp.ge4·;throu~:Jhe_lll?PJication · ·. · ' ' :. of a tonservative approaclnt each stage<of:ihe data, a.ilalysis. The cumula#on ()(there-results
thus proV:fdes:for·the adeq:uat.emar~ of Safety: • ' ' . ' . . '"•:' ''',":' '
. .. ~·· ....
. ·. : .. ~·
.. · · • It should be borne ui rnirld:thilt'thiS document :Ji published. to pi'ese~i fu.fonrmtion.
required:bytheNoise·corttrolAct,SectionS(~)(2),and·thatitscc:)ntentSrl~;not:·9Qnstitute
Agency reguiations or standards. its:statisticai-genetallzations•.should not. be;·~pplled'to a ..
particukr individual. Moreover, States and localities will approach thls iilfru!pation accord"
ing to their individual needs and. situations.
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Foreword-2
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TABLE OF CONTENTS
Section
Foreword .. -.................................. : ........ .
INTRODUCTION ............... ; ...................... .
SUM~IARY ....................................... .
LEGISLATIVE HISTORY ........ , .................. .
ENVlRONMENTAL NOISE. EXPOSURE ... · .....•.•.• ~ ....... ;
RATIONALE FORlDENTIFICATION OF LEVELS OF ENVIRON-. ·
. ..·. MENTAL .NOISE REQUISITE TO PROTECT PUBLIC HEALTH
. AND WELFARE .... :. ...... ;.: .... : ..•....•..•... :.~ .....•......•...
. 'BASIS FOR IDENTIFYING LEVELS ...........• ; ...•.
IDENTIFICATION OF MAXIMUM EXPOSURE LEVELS
TO AVOID SIGNIFICANT (MEASURABLE) ADVERSE
EFFECT~ ; ..... :· .· •... · · ... : ..... ; ............ .-, .... " .............. : ....•. · .• : .... .
··:::Hearing .•.• ~···: .;: :;::·. •:··:: · .•...... ·:; ::.: >. ~ ·; ' .... : .. · ·
. . . .
,·:-' ... Basic Consfd~rati~~s: .' ... ·:: .. ·~ ~-: .. .' ~ >. : .....
'·... .4
· · · · : ·. ExplanatioJi qf lderitified Level ·
··•:. ·rorHearingToss·-;·:·~··; .•..... ; ::;:;·; .. · .... ·, •.. -~ ; __ ·.
Adequate Mat~ ~rsaiety ·> ....... , .... : ..•.. ···
Page
Foreword
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·.. A~tlvity: Interferenee/ Annoyance. ; ... > .. ; ........ . , ..... ·-
... :·.· 2Q-
·-.... _, · Basic Considerations . : . . . . . ; . . . . ; : . ; . . . . •• . . ·
• .. ·· ··-. ,.-.·· · .
20 ·:·:
. . .. · Identified. Lev:els oflnterference ...•............ 21
.· :::: . -:
;:~_=.: Adeq~a~e:M~gm ~{Safety ; .< ...... ·~ ;' .. -... ; ...• .. : .. · ;••: ..
.· . .,.., ......
... MAXIMUM EXPOSURETO'SPECIALNOISES ;' .. : ...... ; ...
~ ' . ·.' ~ . ,• .....
Inaudible Sounds ....... : ·~ .. : ............ · ... : .. ··, 24
:. :Infrasound .. : .....•........... : .......... . 24.
Ultrasound ...........................•.... . '"'4 . ... .
·-. '. . ~ ....
. . . ' . . .
....... ·
_;.:.·:-.-·-
.... ·.
Section • · .. -.. :·,;., .. '· .. ·· .. --:-··. -:; __ : ·-·' ........ :· ~-~'·> : ~-. ... ·; :-.::•-·: , .... _: .. ··,-.;_:_
:· 2~ · impulse Noise ~·:.·~· :·::: ....... ·.>>:·~··::.~·.-.-.·/ .. : ..
" . ·:·~· •. ~ .. ti!~:~~i~rj~'s~~:·::: ::· · .. · .. :. ···
··Page ....
2'5
""5:·_· ... ···-·:· ...
. . ' . . i7 .....
: ·-· .. · . .; .. --:; ..
27: ... · · · · ·· · · . . . .. :c_.:: SoniC: :S9p~s: ~ .:·. ·~-·~ .•.. ~ ...... ~ .. ·-........ , ~ .. ,/•~:~:·. · ;·~::.~.:;; . .:: ... ;:.< ::·· ·
IDENTIFIED; LEVELS OF.ENVIRONMENTAL NOISEIW: ,. ·· .... ·. . · .· ·· .... · ,· ...
DEFINED AREAS ..........••......... ~ ·.·.·.: .... ~· .. ·.:.: .. :.: .. ~-.. ·· .. "··· .•. , .•_ · .. . 2.8
.:· ..... ·.:·'·.···
INDIVIDUAL LEVELS.:·:·:'> ... ;;.--~ .•.... :~~-~.~~:',.::·;:.;.: . .. . 48 .····
:~ . ·•
. USE OF.IDENTIFIEDENVIR()NMENTAL NOlsELEVEis'
· ..... _ .. _.·:--. -·,,.·. :,·
':· ···•Jt
3'3'·
GLOSSARY ....................••.•..•..• : . .,._ •...•. · ..• ·.~·. '··:: ""9'i9.ssary;;I. .. .· ..
:. ': .. _-. _; ~.. . . --. : :'; .. _; :_.
~PENDICES · ._: .. ___ .:-·:·,,_
::F:··--._-
.. ·
,.;,,;
EQUIVALENT SOUND:LEVEL AND -ITS· RELATION/ ... ··-. .
SHIP TO OTHER NOISE MEASURES .• ; . : ;, .. ; ; .... ; ,' .:. · '
·. . --··: . . .: .. ·:-·-.. ·
LEVELS OF ENVIRONMENTAL NOISE IN THE U;S.
AND TYPICAL EXPOSURE PATTERNS OF ·· ·
. INDIVIDUALS .. :. :.~ ... : ..... : ,,,.:> :.~.:: ;;"~ .. ,~.~-•... ~ .:;·.,·.:':, .. :· B~l ..... •
.. ,_ .. ·. · ... ' ·.· .. -· ... NO~S~~~~J? UCE~·~~-~~~r~J:,O~-· :._.:~_:: \:.~:·,_: .. _:~::::: >·:·.•·· .. >::_:.;;}~~· .. z ::;:~·:=;':/ .... :::;:: C-l
NOISE INTERFERENCE WITH HUMAN ACTIVITIES•:AND· .· ... ·
RESULTING OVERALL ANNOYANCE/HEALTH;· ···· ... ·. · ·•
EFFEctS . . . . . . • . . . • . . . . . . . ...... ~ . . • · .... ~ . . . . · .... :,, ......... ..
' .. : . ·. ·.. .. ._. ~ ·. ·. -::· . . . ·.:: .. ·•.· .
. . .. GENERAL. EFFECTS OF NOISE NOTDIRECTLYUSED·
IN IDENTIFYING. LEVELS OF NOlSE':REQUISlTE TO.· ·.•·•·
PROTECT PUBLICHEA.LTif. AND. WELFARE . ~; ... ~-~:: •. , ..
>EPA's RESPONSIBILITY TO· IDENTiFY SAFE LEVELS, ··-·
FOR OCCUPATIONAL NOISE EXPOSURE ............ .
iMPULSE NOISE AND·OTHERSPECIAL NOISES ... ; .. .
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AAOO
AFR
ABBREVIATIONS
American Academy of Ophthalmology and Otolaryngology
Air Force Regulation
AI Articulation Index
AMA American Medical Association
ANSI American National Standards Institute (formerly USASI)
ASHA American Speech and Hearing Association
. . .. CliABA. . Committee on Hearing and Bio-Acoustics
dBA' · ·A-weighted de'cibel(decibels). Also written dB(A).
EPA Environmental Protection Agency
IEC · International Electrotechnical Commission
ISO . . International Organization for Standardization
NIOSit · · · Natfbna:llnstitute for. Occupational Safety and Health .
NIP:TS
NITTS
NPL··
NR
OSHA
.Noise-Induced Permanent Threshold Shift
Noise-Induced·T~mp~~ary Thresh_old S~t
. Noise P61lutiop Level· (alSo National PhysiCal Laboratory m England)
Noise Rating
()ccupational Safety and. Health Act .
~s ·:. . . RootMea:n Square
.;._, .. _,_·..-·.·· .. · ... ····.. . : ·:··.:.; ..... . ··:-. ·.·.·:·
SIL .. : ·. -~-., ·-Speech futerference Level
SPL Sound Pressure Level
TIS ~Temporary Threshold Shift
Abbreviations-I
Ill
..:·.···· ..
TTS2
L(t)
. LA
.:·.'Lb.
·Ld· ...
·.· Leq;
Leq(8)
. · Leq.(24)
Lh
Ln
: ... Llll!lX
.... _::,t,;/ .·.
· TIS determined 2 minute~ after cessati?n •of exposure
· Time-varying noise•Ievel
._,_·• .
· .. _; .. _:._:. ..
:·•; .. · · .. , -.. ····
"Background"·. or-''t~sidual" s()undlev~l.A~eiih~d . . .. .. .'.. ... . . . . . ~ ·.. . •'. . . . ·'. : .. · ~
. Da~ime· equivalent A;.W.eigh,ted,soundJevell;>~tW.een;the.·hours~Qt:o:to():and ·
2200. : .:. . . '• .: ... : .. , .
· Saundexposure.lev~l::._the"le~et-of•souzidaccUiritiiated•·duriliiil" W.ven·event. . . .·· ...... -.. . . .· · ... •;.· ··. ·. . . . -.
.... ..•. Day-rilghtaveragesouD,"dJevel=the·24hoW":A-weighted,~Uiva:J~~scnind.level, .
with a•·lO decibel penalty· applied to ttighttline.1eveis; · ··· · · · ··
.•. EqUivalent A-weighted S9u!ld· ~ev~J.:.ovei a giveri tfut~.inttdva!:L• · ..
.:.,_
Equivalent A-weighted sotind Jevei over eightb"burs. ·
... · ·.. ..: ... <~ --:. ~. ·: . ·.-:~··~·:.
Equi~e~t A:w~ighte<isound)~Y.~l··~~~ -~4-hoots· · :·· ·
. ~.: ...
.. ,._
Hourly equivalent A-weighted sound·teVet··
Nighttime equivalent A-weighted sound l~el betweeri the hours>.of2200 and
0700 . . ..
. . . -:. .. .::-~·.
·. ~xunuril A-We~hted s6tfud ie'Velfht a given :tiriie intety~J/oi ~vent ;
. X.;pereent sound level;. the A-weighted-~oun<i.k¥etequa~ Qf~xcee#~d:x% of
time··· . . ·· . . '" .. · .. , . · . . .. · ·.·: ,-:··
. .. . ...
Difference: in decibels .betWeen·-two··differentA~w~ightea~~owid le\te]S-; ·: :: .
•• ::" •• •• • : :-::.:;.~;.: • • 0 \• •• ;. '·, ••• ~ ·····-· ;· •• ·~:.:.·:_._.,.
: .•·. ·.-.'.:.: ':. '.:~·.: ·-:~· ·::;.:-_i:::l::·:; • ..:i~::,-..... ,. __ .. -.~ · •. -;-~
. :. --~ .. '
::_ ... _ .. , .·
Abbreviations-2
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Section 1
INTRODUCfiON
The Noise Control Act of 1972 establisheti by statutory Il}andate a national policy "to
promote an environment for all Americans free from noise that jeopardizes their public
health and welfare". The Act provides for a division of powers between the Federal and
~tate and local governments, in which the primary Federal responsibility is for noise source
emission control, With the states and· -other political subdivisions.retaining rights· ilhd auth-or-
ities for prl~arY ~sp~nsibility ta· control the use of noise sources. and the· levels of ~oise. to
. be permitted in their environment.
·;._ .. · .. ..-;·.:
In order-to provide adequately for the Fe-deral emission control requirement and to
insure Federal assistanc~ and guidance to the stat~ and localities; t.lte Congress has established .·
two separ.ate-.but related requirementS: With regard to ·scientific ·information about health and .
welfare effects. of noise.· F~i, the Environmental Protection Agency was called upon to .
publish descriptive data on the effect of noise .which might be ex.pected from various levels
an:d exposure situations. Such "criteria" statements are typical. of other environmental
regulatory schemes. Secondly, the Agency is required· to publish "information" as to the
levels of noise "requisite to protect the public health aild welfare with an adequate margin
of safety~~~--<'. · ::·: .... -. ·=·· ·:·.. ·--· . .. . .... ·-
.. -.-;,-
SUMMARY
The first:·reql.lifemeilt W~~ co~pl~t~din July, 1973.; :whim the document '"P~blic Health .
and Welfare criteria for Noise'~ was published~' The present document represents the secortd
stei::i; _Much·,ofthe.sc~entific material. on: which this document.is based was. drawn from the
earlier "criteria document". while additional material was gat_!lered from scientific publi-.
cations and other sources) both from the u:s .. and. abroad. In addition, two review meetings
were held which\\•ere· attended 'by· representatives-of the Federal agenCies as well as distin-
.. gillshed.membersa:f-the.professionat:ca:Iiullunity and.repr.esentatives from industi:ial and
·.; environmental.'ass()C~tions. The.r~viewers~ suggestions,.both.oral and writte:n,,havereceived
· tho~ghtfuLattenti~~ ancl their ~mments:incorporatedto the extent feasible· and appropriate .
. . _-... ; ';:•. . . ··-. . . . -. ·-. -· .. -. .... : .. .-.· ·,···--.· ·. :'.··;·.: :• . . :.~·-.;, . ~---·. . . . ·: ~ .. ·... -. . ..
After a ·great deal of analysis· and-deliberation, levels were-identified to.protect public
health and welfare." for a large ntimber of. situations. These levels are subject to the
-... :·.. . ····:• .· ·... : · .. ·· -
· .. ·._.
. .;·.-...
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-·.;·
. . . ~ '.
. ·.;;-.. ;,, .. ·.
.. · _ .. ·: _:;~ .
·.defutitionsand qualifications-contained, fu· the Foreword, They· are ~mmarizedin·Table 1
a~coi.dmg to ·the publiG h~lth.ancl.wel{are;effee£Jq~.b~·:,prot¢pted agafust,-.·the,.re.quiS{te : ':
•: · .. sound level, andtne iu-eas w-hich•al'e· appropriilte for· such:·ptotedion~_:·.· :· ·:.'~-"~-""~ ·: :
•: ~--.···· .. ' '·~ ;_-:.
:· ... ~ ·: ; .. : .
In order'to·identify these 'leve~·a-:rtuijlbet:.of consroeratiOp$ an<f,hyp<:)th~~s were neces-, .. ·
sary, which are listed below with reference to the: appropriate appendi(;es\vber~ .they are: dis~ . ·-:cussed ih detaiL ·. · .. ;: · ~·-·'···.-.-:--.. -·· ····
;-:;. .
·: •.. l.. · In or.®r_todesaibe:~ eff~~-o~envir6~~~al~~in:a·~~;~~orln and:· ...... ..
· ...
.........
appropriate way; the best descriptors are:the long:oteim eqUivalent'A•weiifited so\U:u:l:-.level . -·: .. ~-..
. .(Leq) and:a varjation.with a nighttfrn~:.weigbtin~,tlfu.:~~~_ts()un~kleye!-tSi~l{s~e A~l'en;_.. .
...
dix. ;\). . . . . · · ..... ·'·" '· •·•·"'· ·; . .;.:,_. :_,_·,.,., •. ,:;;:::)'.;,•.c,·-: .. ,, .. _,.. ... ->:,.·::. ·.
• ,·: ·.· .. . . ._ .. ·-····· ·' -~~~.·· . ' :.':·<;;.:.:_; ... , ~:: .. :,(~--~~-.:... · .. ,: ·· .
...... ·. ···•.·•·. :·~··. . ... ,.. :;·~·:..:~: .. : ·::;.=;;._:,~·~.,., ·-.;-:::-.~:~·~.'-:;.\_-.•.: .•.... -··.;.·. . .
2. · To-prote~t against hearing irtlpaitmtmt (see Appe.ndix-,~):::;, · . . . . . . . . . . . . ·. . . .. ~ . . . . . '.·· ·• ... , . . ..
··.-·,;.· .. · ,· :· .
· ....... :-.·
·.·· ... · · · · a. · Theh~an,ear,whdt-damag~dby:noise;is•t:ypjca1JY::atf~¢te4fli:~t;atthe ·
audiometricfre.quen~y of 400PJu,~: .;,~· ·····.. . ·;: :;:_~~: '-:-:···,.::;.:.:· .•.. ·._ ... _·., ~:;._. ,~ .. <·. __ : ••••.• -· . ---·
:·:-:
_b. · Change~ fii h~~g '1ev~f~f'ie8S than·S·dB ~~~eribrJi:·~~; .. ;~~~~~ . · . ·-.. ·. .
· ··.notiCe3:-b1-e,Or--sigiu.ficari-t~-· ·. ·-:·:~--·_·:,· .. -... ~---· ·>:: .. ·· · , ~. . <::· · ··_·_=-::· ...... ;/-~ _:_<·:-._.,. · .. _,
. . .. ' .
-~ One.cannot be da~aged by sounds C()nsidered·normally-audibie,:which one
cannot hear.
; ' . ,.._ ._; : ·: ., . :~' . · .. :.•
· ·····'d.. Protecting: the -~pulation·up..tp. a_a.itical pen:e~tile (~~d·~ceorcling to~· . ··, ···
deCreaSing ability to. hear). will alSo protect those above that pei-6:;1ltil'e: (fu oV-ie~ of con-....
.. , ..... · . ~ .:: ... sideration'2c abo~) -thereby·· prot~g:Vi.ituany. the-en-Qre ·pOpulatioiL:::\ .. :~~;.·:::.: .. :.; · ·'• .. ; :c.< = ..•....
--... ~· ..
··:.-.
.. ··:··,·:
... ' .. : .. ···;.· . ·· ....• · ..• :. . ... ·-·~·!_·: ... ·
·.·:··,.·:
·-: ··. . -
a. .. The Equal EneiW Hypo~hesis ......
-_:_.,,
"·:. · .
b. The ITS Hypothesis . :. ·. ~ .... ·.: ·... ,. _..,_, · ... ::_~
._..-·.··.
4. ·· To-identify levelsrequisiteto protect against activity interfere.nce (seeAppendix. D): ·
. . . . .
a~ Annoyance due to noise, as measured by community su.tVe~, iSilie ;,:ns~
quence of activity -interference.
b. Of the various kinds of activity interference, speech interference is the one
that is most readily quantifiable.
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Table 1
SUMMARY OF NOISE LEVELS IDENTIFIED AS REQUISITE TO PROTECT PUBLIC
HEALTH AND WELFARE WITH At~ ADEQUATE MARGIN OF SAFETY
(see Table 4 for detailed de~ription)
EFFECT LEVEL AREA
Hearirlg. Loss Leq(.2 4).;;;; 70 dB All areas
Outdoo~ activity .. Ld 11 . ..;;;.ss dB Outdoors in residential areas and
interference and farms and other outdoor areas
annoyance· •. ·.·•· . where people. spend Widely varying· ..
amounts of tinie and other places ' ... .-:· ... in.which quiet is a basis for use. --.-. " . ..
. ..
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., ..... ,. Leq(24} ~.S.S_dB .: Outdoor areas where people spend . .. ... ~ . . .. llinited amounts of time, such as .. .,
·-·. .. school yards, playgrounds, etc.
... . , .. : ~ ' ..
Indoor activity· , . Ldn ..; 45· dB .. Indoor residential areas
interference and
annoyance .. Leq(24)..; 45 dB Other indoor areas with human
-··· . activities such as sch()ols, etc ... ,
... -··.· ...
Explanation of Table 1 :
1. , Detail~~ .discu,ssi?~s o_r the tei"IJlS Ldn ~d ~eq appear later in the document. Briefly, .
. Leq(24) represents the sound energy averaged o~er a'24o;houi" period while Ldn represents
the Leq wifua, 10 dB nighttime weighting. · ···
. ·. ·-
2. The hearing loss levelidentified here represents annual-averages of the daily level over
.. a· period of forty years; (These are energy averages, not to be confused with.arithmetic
averages.}.:
3. Relationship of an L~(24 )'~f 70.dB to hi~er. ~xposure 'levels.
. . . . . . . . . . ·. . . . . . . ~ . ' ..
EPA has determined that for purposes of hearing cO:iiseivation alone'~· a'leveLwhi:ch is
protective of that segment .of the population at vr below the 96th percentile will protect
. virtually the en~ population·: 1:1Us lev\!1 has. been calculated. to be an L~q of 70 dB ()Ver
· · a 24-hour day, · · · · ·
.. _·,_ ··· .. :·.·._
3
··.·
·-:· ;.:
Given this quantity, it is possible to calculate levels which, when averaged over given ·
durations-shorter than 24 hours, restilt·m.equivalent amounts of. energy.. ·:For·exlilnP!e~· the
energy contained in an 8-hour exposure· to 75 dB is equivalenrto the-energy ¢q.ri,tiiitieditra::.
f4-hour exposure to 70 dB. For·practicalpl:li'pQses, the fonnere,1'pos~is·<o~!Y· ~qlJ<ivaleil.t.
·_ ,. to the latter when. the. average -level-of the r~mainfu({i6'11()u:S P.er.: dayjs fie'gugibk:({;~~; rio(;: ...
more than about 60 dB* for this ~). :. : •· · _. . _. . ..
. . · ~· ..
.... . . . -. :~' . . .
~ :''.
These levels are riot to be. construed as standards as they •do .not take into acccnint cost' ··
or feasibility .. Nor should they be thougllt ofas:discfete :numbers, sirt&:they:ate';des~ribecl .-
,. in terms of energy equivalents. As specified in-_ thiS. document; it is EPA's Judgment that the:.-·
-maintenance of levels of environmentarnoi~ at' rir below tliose si>ecmecfaboveal'e requisite
tb protect the public froin advei:se health· and: welfare effects.·-Thus, 'as ariindmdual mbves .-.
. from a relatively quiet home; tmough the: trarispoii~tion: cycle, ·to· a soinew1tatrurl$ie:f-o~cil.: pationalsitUatio~, and-then back'hofue'agafn, hls.hemng will nolbe'imp~~ifihedaily-> ·-,,; .··
equivalent of sound energy in his environment is no more than 70 decibels; · Likewise, undue
mterference with activity and annoyance will not occur if outdoor levels are niaintaifled at
an energy equivalent of 55 dB and indoor levels at4S dB. However, it is always assumed
tltroughout that enviroJ1mentalle:vels will fluctuatei evenJhou,gh ti:t,eideiltif"!ed .energy e.qlliv~ ·
---. .. alent is·not-excee.ded. ·Lik:ewise,.human,exposure to .IJ-oise. W.illvary: 4urll:lt.-th~·day;•even :-
thO-ugh the daily "dose'~ may correspond well to theidentifi~d levels.· --·
...
· · : ,. . . . Before-progressing further; it·woutd·be helpful·to·diirere11tiate between' the--ter1lt; '·' ·-
--. "levels''. '!exposure" and "4ose,.; As used in tbi$ document;the .word:~~l¢ve!f' refers.io -th~. -. __ -
. _ · --•-·magclttide of'sound~ ·iil its physica(dtinensi<n1~ whether oi'•n:ot there ~-h~·.pr.~~rii t~ f• __ ,_," • · · ·: hear it~ "Exposure'~ is used to mean those· sound 'levels which ate transrmtted t~ th~ hum~ · --
ear, and "dose"is the summed exposure over a perio_d oftiine.
·: ... ,
* This is not to imply that 60 dB is a negligible exposure level in tenns of health and welfare
considerations, but rather thatlevels of 60 dB make a negliglJle contribution to the energy
average of Leq = 70 dB when an 8-hour exposure of 7 5 dB is included.
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LEGISLATIVE HISTORY
Pursuant to Section 5(a)(l), EPA developed and published on July 27, 1973, criteria
reflecting:
... the scientific knowledge most useful in indicating the. kind and extent
of all identifiable effects on the public health or welfare which may be
expected from differing quantities and qualities of noise.
Under Section S(a)( l), EPA was required to provide scientific data that, in its judgement,
was most appropriate to characterize noise effects.
The present"levelsinformation"•document is required by Section S{a)(Z),,whlch,caUs·
for EPA to publish, · ·• . .
. ; .· ·.·,. . .. ··.·•··.
•.. information on the levels of environmental noise the attainment and
: maintenan-ce ·of which in defmed· areas-under various-conditions are requi~ · · ·
site to protect the. public health and welfare with an adequate margin of
---------
·:_S3fety> :_. :." .. . . . . . . ·. .. . .. __ .... · -, .... ·. ' ....... ~:: ...... , .
The present docunient, arid its approach to identifying noise levels based ori cumu•
lative noise exposure is in response to the expressed futent of the Congress that the Agency
develop such a methodology. The EPA Report to the President and Congress, under Title
IV, PL 91 ~604, contained considerable material on the various schemes for measuring and
.evaluating c&mmtiruty.noise.,response; and it.contained a r~qmmeildation that the Federal.
governmertt should make an assessment-of the large number ~f-varying systems:, with. a goal . ·.
of "standardization, siJnplification, and interchangeability.of data".
. The·need.forstich, actio~ w-asthe subj~t o(co:rtsiderable Cc;mgr~ssio~arintere·st in the
hearings on the various noise: control:· bills; whicli-:fuially' resUlted: in, enactment of·the Noise
Control ACt of 1972. The concept underlying this present document can be better apprec-
1~ted ftom .the foUowfug pertinent elements. ofthe.legislative .. history of the Act... · ... . . .·~ ..
In the courSe of_ the hearings before the Subcommittee. on Public .Health ,and .Environ-
ment of the Committee on Interstate and Foreign Commerce, House of Representatives
("Noise Control" HR Serial 92~30); the subject of the. r~lation of physical noise measure"'·
. ments to human response was given considerable· attention. The· Committee, in reporting ·
the bill (House of Representatives Report No. 92-847·; Noise Control Act of 19,72); stated
the following on this matter:. , ... · .....
The Committee notes:that most of the information relating to noise
exposures was concerned with specific sources, rather. than typical
. '· . . . ,. ·.. .··.·· . ·. .
5
. '·~··· ...
.. :.·' ._ .•.
. :;·· ... ;·.··
~. ·-:~··.·.,.-~-.-,; ..
cumulative exposures to which urban and suburban dwellers are· .
_commonly exposed. There isa-neecifor•rnuch greatereffoi'f.to.: -
determine the magnitude and extent of such exposures, and: th;e~. .... .
Committee expects th~'EPAto prorn<>ct~ stitdies On this subj.e.et·an<i: .. .
consider development ofrilethods ofunifotrri measurement ofthe .... .
)mpactof)loiseqncommunitie~. ·--·-:·>'. · ::.~: :: .... ::.. ·•· .-':'
. ·.· .. :.·· . :·. ·''' : .: ..... :··-.:··,
•• ·,:• . . . •:;.~····.i;•·.;~ :.·~ ':). :--. '
·._.· ...
The Committee went ~n iii the· Repoi1 to ~~gn iesp9~~fbili~y to:tp~.f:\.d.lrlinis~~torto,c
. coordinate all Federal noise programs, with_ a spe¢fic -expression of oon_cem~o~t}rt.ije . ·.-..
·< ' "different systems of noise measurement" in use by 'the' various· Agencies:·: Th~'iollowing
.... ,. ·., : ... :.> is: especially important With resp~cttq tl:le. purposes Of this.d.Ocuntent:.: "· <<:L : . :>'::·:". ,.·. . . .
_:.· .. ::'•".'•··· . ·.·. ,·: .
. :."":·--·· .. · · .... ~ .. .;': · .... _ .. . ... :.··
The Committee gave rome consideration to: the e5tablishmentot~::~·~---~'··· ·~ · ..
'· ... · .. ·.;.·.·,.· .. · ·. -Federal-ambient noise: standard,. but rejected• th~·:concept~-:~ ... , ··::~-.. .-, •·. ''''>f· .. ~-.·
·-·Establislurient of a: Fedetat·ambientst~n.dard wcniid· in effect:pl;lf·.·:··-····-••--:· -•.
the Federal Government in the po.sition of' establiShing-land liSe' · ··· · ·-··· · · -·
· .. c..
-~'-·.· ... :·.~·-: ... •.
. . . : .. : . . . ~ ..
-· •·> ,zoiting requirements-on the basis .o.f n9ise~· -~·;.At -is the Co}llnuttee~s· .
. . . . view that this function is one more properly -of the states and their ..
·-·political-subdivisions;-and:thatthe F.ed.eral·Government shOuld.pr~····._
Videguidanc~ arid leadershi:Pin.undertakingthat-effott~ ·' ·._ •-· · ·
·: ... ·.
~ · .. ·. . ·: ~:; ~ ~. -~ ': .. ·:·: : ::· ..... '.. • ...
.· .....
.. ~·;
The need· for· EPA action on this:subject under-the· legislativ~ authoilty oUhe-.Act wa~
presented in Agency testimony before the Subcommittee on Afr and:Wat¢rfolltition;Com-
inittee on Public Works, U.S. Senate. The following portlonis important(J'..i~is~ :Pollution
Serial 92-H35 U. S. Senate): . · · · · ·. . . .. . · ·. .
,,,;,·: .. -. ... ·.··.
... ····· ... :
·A ~ariety ofspecialized schemes· have ·b~··eyolv~· ov~· the:pa~f/ ,.:
years to quantify the relationship between these various condi" .·.. .
tions and~ their effects on humans.-, ...• ·S-uffice: it tc:fsay~thafno: '··· .....
sfuiPlistiq.Singk~ numbetsystem, call acJ.equately pfovi9e.fo~·a ; .. :.:. .· .. .-....... .
'uniform acceptable national ambient rioise·1evelvalue: This} -·
. _ however; does not preclude the undertaking-of a noise aba~nt
······ ... _ .. ::·
.. ·. strategy.invo·lving:theproper use-cifthe_available'sciet1-:~fic4ata:: ·~ ,,. ..... · . . on the part of the FedenH GOvernment in conj:1mction' with the ..
·.state and·Iocal governments~ .. ; The complex nattire· of the· cori~
siderations we have outlined above in our judglnentrequfre that
the Federal Government undertake to provide the necessary m"'
formation upon which to base judgmel'lts ....
Taking both the specific language of the Act, cited above, and the legislative history
discussed in the foregoing, EPA interprets Section S{a)(2) as :directing the Agency to identify
· . levels based· only on health and welfare effects and not on techitical fea,sibility or economic
costs.
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Throughout this report, the words "identified level" are used to express the result of
the inquiry mandated by Section S{a){2). The words "goals", "standards", or "recommended
levels" are not used since they are not appropriate. Neither Congress nor the Environmental
Protection Agency has reached the conclusion that these identified levels should be adopted
by states and localities. This is a decision which the Noise Control Act clearly leaves to the
states and localities themselves.
Certain of the statutory phrases in Section S(a)(2) need further definition and discussion
in order to make clear the purpose of this document. Congress required that EPA "publish
information on environmental noise" levels. This mandate is basically one of"description".
Such description is to be made in the· specific context of "defined areas" and ''under various
. conditions". The phrase "in defined areas. under various conditions" is used in both a geo-.
graphicaland an activitY sense, for example, indoorsin·a school classroom or i:>'u:tdoors adja-
cent to an urban freeway. It also requires consideration not only of the human activity
involved, but also o.Lthe nature of the noise impact~
The next and last statutory phrase in Section S(a)(2) is most important. It is that the
noise· levelS are to ·t)e discussed-on. the· 'basis cif whatis requisite to protect "the public health .
_ arid welfare with -an· adequate margin of safety". The. use oHhe\vords ''public health"
requires a.statisticalapproach.tO'determ.Ule the order of magnitude of the. population ...
affected by a given level of noise. The concept of a margin of safety implies that every
sector of the population which would reasonably be exposed to adverse noise levels should
be included. by the specifically. described levels.
The phrase "health and vrelfare'· as-.u5ed herein is-defuied as "complete physical, men-
tal and social well-being and -~ot merely the absence of disease and infirmity". This defini•
tion.would.take.into account stib:clinical and subjective responses (e.g:, annoyance or other
adverse psychological reactions) of the individual.and the public. As will be discussed. below,
the available data· demonstrate that the:most serious clinical health and welfare effect caused
· · · by noise isinterfer.~rtce withthe·ability to hear; Thu5c, as used in this document, the phrase .
. "health and welfare~•will·necessarily apply to those.levels.of noise that.have,been.shown tO···:·· >
interfere ·with the' abilhy io hear: . · ·. · · -·
Thej>hxase, ~'health and welfare" also' incl~des-personal comfort and V:.~n-being and the· .. -
·. :absence ~fmental anguish-. and annoyance. In fact, a considerable portion of the data avail~ ·
able on the>•b.ealth and welfare" effects of noise is expressed in terms of annoyance. How~
·ever, "annoyance'' is. a description-of the human rea'ction to. what is described as, noise
"interference"-; arid though annoyance appears to be statistically quantifiable, itis a sub~ . .
jective reaction to interference with some desired human activity. From.a.legalstandpoint,
annoyance per se is not a legal concept: Annoyanc'i~ expresses the human response or results,
not its cause. For this reason; the common law has never recognized annoyance as being a
7
..... ·· .. . ··, .. ·
...
.. :-.. ~-: ·' ' : .. ~·
·. ·-~. -----. -:--~
compensable injury, in the absence of interference with a· personal or property right _Of the
many community surveys on noise which ·have been .conducted~ speech· .m.u;J,'fer~~~emerg~s .
as. the -most tangible· component :·or··annoytince,. whereas .sleep .. an_~:-.othei· Id#4~~ 0'·(~4-ijYii:y · ··--·
. _._.;.·.: ... interference are important, but less well-detmed ·cqntributors. Thus; altho~ .it ~,illtportant:·· -.
· · tq-.:·uncterst2rld th·e unPor~ap.ce. or ·annoyante.·as-: a cOnCePt;.-if i.s· the. ~:ct~~~J--#t~r.ret:ence-.. Wt:ilt:. ~;-:_~<:·:-~::·· ·:-·-
actiVity on which the levelsidentifiedui thiS-documen-t~ bas~.'· . ···· · ·· ·-.·.··. · . . . : ... :. ·. · .. ·-. .
_:.··
. . . . An even more imppn~:~. but related• :pOint ~)lsthe kept in In:Uld Wh~tt.'tiui docUment ,;• _··· ..
.. is read. The data o~ which the.infonnational i~els.' in··thls document are .. based are rtb:f••sholt .. -. . . --·
run" or smgle event noises. R~ther, they represent energy equivalent n~i'se leve~ o~er a'long : · · · :· · ·. · ·
period. For example,' the exposure period\vhichresults iii· no mote•than;S dBheannglossaf ..
the identified level in Tables l and·4 iS a period-Of forty years>'·' .~ " ;·:'''':,'· · ;; · .. · · ·. ·.· · ';.c-:.-' ..
. . . ·. ~--·. ' .
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.. ~~!•.;•;;~o~·;:,~,::;:;:;~:~::::~~~ij~~o0-7.:~:3 .. . ' · lJ
.· ·character of sounds from all.sources; .; As discussed earlier; iti~ th~~intent o.fCQligress.Jhat , · · · · ~ ~;~:~ ~
. . MC!riy.noise rating and eValuation ;rocedures are available in~~ ~t~r~tiJ~;2~l ln~lun-. ' ·. ·
.tary national and internationa:l·standards, and in commonly used_•engineerin~practices-(see
Appendix A)~ These_ methods and practiees are well established, ~d it is. not the·purpose of
this document·to list them, elaborate on.them, or bnply a restriction of theit use. Instead,
· the p1.1rpose is to discuss levels of environmental noise using a measure which correlates with
other measures and can be applied to most situations. Based on the concept ·of the cumula-
tive human exposure to environmental noise associated with the various life Styles bfthe
population, maximum long-term exposures for individuals and the corresponding environ•
mental noise levels at various places can be identified. It is important to keep in mind that
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the selected indicator of environment noise does not correlate uniquely with any specific
effect on human health or performance. Admittedly, there are uncertainties with respect to
effects in individual cases and situations. Such effects cannot be completely accounted for;
thus, the necessity to employ a statistical approach.
Section 2 of the report addresses the details of characterizing and measuring human
exposure to environmental noise. The equivalent sound level (Leq) and a variation weighted
for nighttime exposure (Ldn) has been selected as the uniform descriptor. The relationship
of Leq and Ldn to other measures in use is analyzed in Appendix A. Section 2 and Appen-
dix B further detail the various human exposure patterns and give simplified examples of .. ··
individual exposure patterns. The problem of separating occupational exposure from the
balance ofenvironmental exposure and the .statutory responsibility for controlling occupa-
tional exposure is· analyzed in Appendix F.
····-·.
fuBectiorr 3, catise and effect relationships are summarized and pr~ented as the basis
and justification for the environinental.noise levels identified in Section 4~ Specifically, Sec-:
· · · tion 3 ~eve lops ·conchrsions with regard to levels at which hearing impairment and· activity ....
· interference take place. These are discussed in terms of situational variation and the respec-. .
tive appropriateness ~fLeq and Ld:ri· The factors prti.vidfug for an adeq·uat:e margin ofsafety
and special. types. ofnoises are discussed; This section makes reference to material in Appen-
dices C (on hearing lo~s), D (annoyance·m:tdactivity interference) and G (special noises),.
which in turn rely upon material presented in EPA's document, Public Health and Welfare
Criteria forNoise,2 towhich the reader is referred for more detailed information.
Section4 discusses the levelS of environmental noise requisite to protect public health
,. and welfare.forvaricn1s indoor and outdoor areas in the public and private.domain in terms
of Leq and Ldn.· The. summary table. is supplemented by short explanations.
·::··. :;·:~:··. ;;•_, .. -:· . -..... . .-., -:··.· .-........ .
·_. ,.·
· ft is obvio"us that th~ practical application of the levels· to the various purpqses out-·
lined earlier:reqttifes. consid.eratiorts .of factors not dis~ssed here: Alth~ugh some .guidan2e
in. this -respect is. included iri Section. 4, not:·all proble_ms .can. be anticipated~and:some of
.· .... ·these question::; can.:only be resolved as· the inforrnatiotf contained in this report is considered· .. ·
. and applied-; Such-practicarex.peJ:iences co~biried with. resufts offurtherresearch. will guide . ·· · . ·:
EPA in reviSing and updating the levels .identified. In this reg~d, it should be recognized that
certain.-of the levels herein might well be subject to revision when additional data are
developecf;·· ,. _,.. . ·:'~·. : .. ·· ·.·. ·.... . ·.· ·· . · · .. . ···-:···.·.
-.. ~
·-.· ..
. -·· .. .; ..
9
·.; ... _.
>--'
.·.:.··
. , .·-··-· · .... •.·· .
'.:.· .. ·.-·
·.•··. ··,· .. ·_.·. -·:·: ...
·."·:;'·'·;; .. . .-....... ·:·· -:.-·:··.~:·
. --::··· ... :,· . ; . ,: ~ ... ··.·.• ... ··~··· .. . ·.'· .: ~. ... . . . -.
......... : ... :·· · ..
-:. ·>··· .. , .. ··. ·:".:···
. . . . . . . · ...... , ·. -~ :=···
•'.0:;·.. . ••••· . ·. -· .... ; ... • . . ~, ,:., :_', • .. : ... ·.::-.: ...
=-;' . .•:•;·.
.. ·: ... :_.: ....... · ...
. .. ·.·~ :·· .:· ENVIRONMENTAL NOISE.EXP:OSURE
. ·. . . . .. •.: .. :' ..... : .. ~·:. :.· .· .:. .. ... ·: . . ... '.. .... ... : ..
. _ .. -~ .....
... , ...... ' ·:··.: . ... -.
. . . A .complete· physical' des~ptlon. of a sound'must des~be its magnitude; itSfre;: ·.
•· . quency spectrum; and the: variations· of both of these: p~ameters in time~,<£19\feyer,. one
must choose between the ultimate reflriement in measurement techniques and a.:practical
approach that is no more complicated than•neiessaryto.precUcitll~Iinpacfof"n:ois{cl"n .<
· · · ··· ·· . people.-.The Eri~rormtental :piQ~ction Age,ncy•~ ·ch6iceJof::tM ine~s#ie~~t:~i~~nY.tron~::
mental noi~e is based on the following·coJ?:siderations; , · · =· .• , • .. ;,,: ..
.. ~: :
.·::'." ·''.····.
1. · The me~e shbuld·be ~pplicaQle t~·the:evaluatiorrOf:pefY.aSiv:e:'~gitenrr.noise·
. m;.~~ous.~fined::¥eas -~d U!14er -Y.m?.o~.,~()~~~~i()n$·Ov~r,:·lj.~7;8:~~~~\.~~-,~~'~·~··,,;;_;.'::····' ·~:-:'·;:, ·
· 2. The measure' should· correJate weU .. with,Jmown:;effect$•ofLthe npi,Se:e~Vfrotunertt ·
On.theindiVid"uat'and·the·publi~~ . .. . ·· ·.>.~:'' '''•:, , ·'''' · .. ',,.,.
: .·.··. :·· ..... .. . . : '"<•;--:-:~~~-.:·~ ,. :_.~~~:':·.:·-~~i!~~~};:;;(:~.~>-. . . , .... ;.· 0
3. · The measure should be Simpie, practica~ f1t1dacC11r;ite~In p~,c:ipi~Jtshould be ·
useful for planning a.Swellas for enforcementormonitoringpurposes.. ·. < .. :·. · · · ·· •• ·
" " ·, . ;:· ~-· .. · ·_, ... ·-.-.: .. · ·. _.,~··:·~ ... ·.~ .:.; ,. '. :. '<·:>·-' •.::::·· , .. • 0 · . .-·: ·.~ .. -.,;: ~· :...-:·~··. ··:; ~,· ~ ·.:·, . ,1 :<: ";~~ '.' ~!:;:_;.:,::-i:\\'f_..\,';:;":7.~~~~~'~C:·:;~·:~;: .·. '• :·:, . :~: \
..·.':
····· .. " .·. ,,., ... !if\~.;~;;:.~~"·~.,;pm~t.~tli.~ed~~-~-·· ... .
. :.<_,_ 'ti,.:>:·::~.:··. : :.: ... '· · ..
. ·.·. · ... · ·6.·····~·::~~~--~;~--~easure· of··n.~··~;-~:·;v~~~·ici~~i~k··~~~i~:be·;;~~iU~4~·~i~~::·:· .•. , ..• :.,
acceptable ·to-lerance,from: knowledge_ of the phySical even# producillg the' n6ise> · . . . ... · .. ·· ....... :·.. . . ~·~ .. : ~. .. : .. ':
.. . : .. 7: ': . <The·measure shotild)erid itsfhf:t~·s~)unple ~onit~~s ~hlch ·~ ti~·left .•.
· unattend~d in public areas for long periods of time. . . · . ··.· . .
.. ,::·"
These considerations, when·coupled: with the physical attributes ofsound·that in-
fluence human response, lead EPA to the conclusion that tliemagnitude-ofsmi.ii.d. is of
most importance· insofar as cumulative· noise effects are concerned. Lorig.:terJit· average
sound level, hen~eforth referred to as equivale·nt sound level (Leq), is considered the bw
measure for the magnitude of environmental noise to fulfill the above seven requirements.
Several versions of equivalent sound level will be used for identifying levels of sound in
10
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specific places requisite to protect public health and welfare. These versions differ from
each other primarily in the time intervals over which the sound levels are of interest, and
the correction factor employed.
Equivalent A-weighted sound level is the constant sound level that, in a given situa-
tion and time period, conveys the same sound energy as the actual time-varying A-weighted
sound,* The basic unit of equivalent sound levels is the decibel (see Appendix A), and the
symbol for equivalent sound level is Leq' Two sounds, one of which contains twice as
much energy but lasts only half as long as the other, would be characterized by the same
equivalent sound level; so would a sound with four times the energy lasting one fourth as
long. The relation is often called the equal~energy rule. A more complete discussion of
the computation ofequivalent sound level, its evolution and application to environmental
noise problems, and its relationship to other measures used to characterize environmental
• noise is.provided.in Appendix. A.
The following caution is called to the attention of those who may prescribe levels:
It should be noted that the·use· Of equivalent soundJevel in measuring environmental·
noise will not dfrectly exclude· the existence of vety high noise levels of short 'duration .. ·•
For example, an equivalent sound levelof 60 dB over a twenty-four hour day would per-
mit sound levels of 110 dB but would limit them to-less-than one second duration in the
twenty-four hour period. Comparable relationships between maximum sound levels and .
their permissible durations can easily be obtained for any combination, relative to any
equivalent sound level (see the charts provided inAppendix A).
.. · .. ··.,.
Three basic.situations are used in· this: document for the purpose of identifying ·
levels of'ertvirortmental noise:
1. _, permed areas and conditions irt which people are-exposed to environmental
noise for periods of tiine which are usually less 'than twenty-four hours; such as school
classrooms, or oecupationalsettings. '.
2. · D~fmecfareas and conditi~ns in whicli peopie are exposed to ~nvironmenta1 · ·
noise for.extendedperiods oftime, such as dwellings:
3. Total noise exposure of an individual, irrespe.ctive of area or condition.,
. . . : ·~. : ~-... :
: ... :·. ~ . '-.~ .. :-. . ... ' ... ;
*See Gi()s~ for a detailed defmition of terms. Note that ~hen the term "sou~d level" is
-.used througho'!Jtthis document,italways implies the use.of the \-weighting for frequency.
11
'.··-.·· ·. ·"··'· :·
.·::··.
.·. '.
. . : . . . .
\': .. : ..... -.... :
..........
......... ,., ... ·.
. . Three versions of equivalent sound level-are used lit this ,document in order to·ac~ .
commodate the various: modes-ofn~iseexposure that:'6cc~r ~-.~hes~.s.i,ti.la*,qs .. J'}tey are,, .· ..
. ::t:::;::,:~::~eri~ds_ort~e ?;.~-~hicli the.~~-.-~y_e~~~d -~!~:;6v;;z:;r:!~· ~fti9t: .. _~_-_ ...... __
·:•",'·,· .•.:.;-· . . ····· .•.. -· ,.· -l<: .. ·. Leq'fof aJ18-h6ut.period::(l.eq(8)): _This'.~ the. eqW.V.~e~;tA~~ted·:-so~ :: •. · ..
level(in de.cibeJS·relative to 20· fui:cropascals) computed· over any c()ntij:urous tiine period"·• . . .
of eight ·hours· identified with the tyPical occupational ex.PoSi:ire. A's, wiillkshowrt i1i · ...
: later. sectiQns·of .tlliS doc~ent~.4q{8),serve~·as~a.b~forAc;tel:\.ti,frihk;-~~n:men~l
. noise which-causes damage ~o· }).eating. . ... · · · · .
. :": .• r:;~
··.:.: ·,·':.
· · ·._ _ 2. Leq for2~hour wejghtec1Jor nighttfu1e expos.Ul"~-(Ldn):::)::hj~;;form~~ rif' .• . .
·_· . equivalent level iS-used h~reto tcililte ·n~,:ui-;r.esidenHarehvfroiimentS.fo''Clu:oiiicannoyi/);·
ance by speech interference• and iri rome part ,by'sleep ati4· a~ivi.ty:'f~te.tf~nce. · Fot these. ·
. Situations; 'where peopie &:e· affeCted by enviromil~rttainbiSe for e;t~rided: p:erlqd~ ~.f .. . fifEi~;E;]i~i:&~::; .. · .•.
intems:ofthei<lng~tenn:yealiyaverageoftheiliiilY.leveK.: · · '··:,: :>' · ·· ·· · ; .. ·
......... · -·· .. :
In determining the daily measure of environmental noise; it is·important't¢ account'-..... .
for Jhe difference in response, of people in reside-ntial; areas ~o·noises.th~toccur4:qring··::: ,
slectping h~urs as compare4 Jo· w~g Jj,~uts. · :Pux;ing t1ig1lt.timet exj~t?.r~.l>a.e:tcgiound: .· . , .
noises' generally.: dtop irt Ievel-f~om =daytiirie vcilues~ . Furth~; thtt a~tiVify;~()fniost' h&use~ . ,, · ·-, : · ·
h~lds decreases at night, lowering_ the internally generated noise Iev¢Is. Thus, noise event~ . · ·
become more intrusive at night; since the·'iticre$e in noise levelS· oHhe:;evei:j:t,;pver back~=· ·
ground iloise is· greater than it is during the daytime~ . ·· · ·· · . . . . ·.·
. ·.· ······:· ............ ·. ·.··· ,·,::::! .. ,_-.::-.--· . •., •:-:. ;,_.·: ........... ··
· · ·Methods f~racco\mtmg for these,dlffe~nces :betw~-dayti~~ ~rtd ,~ghtti~~.' · , ... -: .. : . ·~--:·. ··'.'
· exposer~ ha;e··been-developed in a number of di£ferent-nois_e assessmen{~~thods em-.. :--..
ployed around the world, (see Appendix A). In· gener8!, the methOd usecl.is to c}).arae-. . ·· ·
· terize. nighttime noise as more severe than corresponding dayt$e ~vents; that'is; to apply
-· a weighting factor to noise that in·crease~ thenumberscominensuratewith,thefr severity.
Two approaches to identifying time periods have been employed: one divides the 24-hou:r
day into two periods, the waking and sleeping hours, while the other divides the 24 hours
into three periods-day, evening, and night. The weighting applied to the non-daytime
periods differs slightly amongJhe different co~ntries, but most ofthem weight nighttime
activities by about I 0 dB. The evening weigLdng, if used, is 5 dB: ·· ·
12
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[:.
An examination of the numerical values obtained by using two periods versus three
periods per day shows that for any reasonable distribution of environmental noise levels,
the two-period day and the three-period day are essentially identical; i.e., the 24-hour
equivalent sound levels are equal within a few tenths of a decibel. Therefore, the simpler
two-period day is used in this document, with daytime extending from 7 a~m. to 10 p.m.
and nighttime extending from 10 p.m. to 7 a.m. The symbol for the 15-hour daytime
equivalent sound level is Ld, the symbol f<;>r the 9-hour nighttime equivalent sound level
is Ln, and the day-night weighted measure is symbolized as Ldn·
The Ldn is defined as the A-weighted average sound level in decibels (re 20 micro-
pascals) during a. 24-hour period with a 10 dB w~ighting applied to nighttime sound l~vels. ·
Examples· of the outdoor presentday(l973)-day-night noise level at typical locations are
given in' Figure 1. .
· · ' ·· 3~ . Leq for the 24-hour average sound level to which an individual is exposed (Leq ·
_ :(24)): This situation is related to the cumulative noise exposure experienced by an indi-
.. vidual frrespective -of where,. or under what situation,: this. exposure is received. the long-
. •· ·'term healthand welfare effects of noise on an individual are related to the cumulative
-· . noise exposure he· receives over aJifetime.
_: '.>. ···~'
Relatively little is known· concerning the total effect of such lifetime exposures,
but dose-effect relations have been studied for two selected situations:
· ..... ;::
·a... . ~Th~ average long-term exposure to noise primarily in residential areas leading
· to annoYa.nce rea~tions and complaiilts. · . .. . . . . · ·
b.. The long-term effects-of occupatio nil! noise on hearing, with the daily
:exposure_ dose based on an eight-hour.work day. . _ .· .
An ideal approach to 'identifying environmental noise levels in terms of their effect on
public healthand.welfiire-would_be to start byid~ntifying_the maximum-noise not to be ·
exceeded by individuals. However~ the noise dosC:rthat an.individual receives is a function of
lifestyle. For example, exposure patterns of'offiee workers, factory workers, housewives,
and school children are quite different. Within each group the exposures-will vary widely as
afi.mction of the working, recreatiomil, and sleeping patterns of the indiVidual. Thus, two .
... individuals-working. in the same office will probably accumulate different total noise doses _
· · . if they iise:.differenimodes of transportation, live in different areas, and have different TV
habits. Examples of these variations in noise. dose for.-several. typical life styles· are, provided _
···in AppendiX K'l:lowever, detailed statistical information oi1 the distribution of a~tuaLnoise
doses and the relationship of these doses to long~teim, health and welfare· effects is-still' miss~
ing. Therefor¢;'a.realistic approach· to· this problem is to.identifyappropriate.noise levels for ..... _ ·-
13
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. ' .. : . .-_.· ..... ·· ... ····
... :·'
·. · ... · ... : ...... · .....
· .... ·
.... :
_. .......... -,·_.-·. '
.. ·.·
.... .-;.·:::
.. ·,· -.· ~:.:, ... -;. ....
. ·:~. . . . . . ·· .... -' . .. .··: ........ ·· .'
' . 'i.d,f: ...
',· ...... :
•.; .. ·.·:. · .. · .. : ···.
·.' .OA:Y.-N~GHT
.. :, QUALITATIVE · ·SOUND· LEVEL'
.· .Q.ES~RIPTlONS ·':··.:.DECI~~~S'. ·
· ..... ;._··.· ...... ;.-·: .... _, ....
, ·::. ouTDoiia LocAiiollis. .
lOS'ANS:ElES~·3ttri=LOOR APARTME~T. NEXT TO
·.,· ..
. ·.··• .. :.· .· .. ·· .
· ....... ':
.. . ... ··.
. .'·1-;.-. ~--......,;.--__,.;·---.· . . ····'FREEWAY' .
""j:---......_.-...;.;.!L;!:O~S~A:!!N!G.~Et:,!;E~S--3/4 MILE FROM TOUCH DOWN AT
· .·.· .·. MAJOR AIRI'DRT·
U)SANGELES-' DOWNTOWN WitH SOME CON-
STRUCTIO.N·ACTIVITY ·
HARlEM -.2nd ·.FLOO•R APARTMENT
. . -~ ;.• . " . .-· ; ": :~ ·."··: ..
~ ; ' ... : . : . . . . . .
..... ··. . •.·.· .... ·:
BartoN ..i.fiow HOUSING ON MAJOR AVENUE -t"-.;;;-----,.---·" ·:··. '' · .. :.-.·
.WAITS-8 MilES FROM tOUCH DOWN AT
:r::.~---· ----MAJOR AIRPORT
NEWPoRt-a:s MILEs i=ROMTAKEDFFAT
. . . SMALL Al-RPOR.T
LOS ANGELES-OLD RESIDENTIAL AREA
··.":
.. ·.' ~ . . ·:. ········
'· .. , 1
·.··
"' .. FILLMORE:: SMALL TOWN CUL-de.;;,SAC
. SAN DIEGO -~W~ODED RESHiE~TIAL SMAll TOWN 'A .;_50~
'. JUH ET SUBURBAN I.··. .· . . : ·-:~: ... . : . :-·':. . .
.• . ..._ ~-.
·.:,.
.. CALIFORNIA·.: TOMATO FIElD .ON FARM
--40-.
.. .;.-
.· ..... · ....
•igure 1. Outdoor Day-Night Sound Level in dB (re 20 micropascals) at Variou:-Locations4
14
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places occupied by people as a function of the activity in which they are engaged, including
a gross estimate of typical average exposure times.
From a practical viewpoint, it is necessary to utilize the wealth of data relating to
occupational noise exposure, some of it, albeit, subject to interpretation, in order to arrive
at extrapolations upon which the identification of safe levels for daily (24-hour} exposures
can be based.
In the following sections of this report, the various modes of exposure to noise and the
human responses elicited will be discussed, leading to the identification of appropriate noise
exposure levels. In order to assist the reader in associating these levels with numerical values
of noise for familiar situations, typical noise levels encountered at various locations are listed
in Table 2~ For further assistance, Figure 2 provides an astimate of outdoor noise levels. for
different residential areas.
Table 2
EQUIVALENT SOUND LEVELS IN DECIBELS NORMALLY
OCCURRING INSIDE VARIOUS PLACES6
SPACE
Small Store (1 ~5 clerks)
Large Store (more· than 5 clerks)
Small Office· (1-2 desks)
Medium Office (3-lO desks)
Large Office (more than I 0 desks) .
Miscellaneous Business
Residences
TypiCal movement of people-no TV or radio
.. Speech at 10 feet,normalvoice
TV listening at I 0 feet, no other activity
Stereo music
(+)These measurements were taken over durations typical of the operation
of these facilities.
15
Leq(+)
60
65
58
63
67
63
40-45
55
55-60··
50-70
~: .. ··.
M
·C:
..5!
~
I
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.5! o;
"'S a.
0 ... .. > ... .. :; e ,. ....
300r-------r-------~------,-------,--------r------~------~
~
!
0.01 '----~--......1.---"'-------l------L---...l.-..L..ii..~J
20 30 40 50 60 70 80
Figure 2. Residential Noise Environment of the N~tio~l-Population As a Fili'-:' -.,_. :·
of Exterior Day-Night Average Sound Levd!:S-.)
16
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Section 3
RATIONALE FOR IDENTIFICATION OF LEVELS OF ENVIRONMENTAL
NOISE REQUISITE TO PROTECT PUBLIC HEALTH AND WELFARE
BASIS FOR IDENTIFYING LEVELS
For the identific~tion of levels to protect against the direct, disease-producing effects-
of noise, protection against hearing loss is the guiding consideration. At this-time, there is ··
insufficient scientific e:Vjdence that non-auditory diseases are caused by noise levels lower
than those· that cause noise-induced hearing loss. In the event that future research renders ·
this conclusion in.valid, this document will be revised accordingly (see Appendix. E). . .... · . .
In addition. to direct disease-producing health effects, interfer;nee by nois·e with various
·human actiVities; such as speech~perception, sleep, and thought can lead to annoyance and
indirect effect~ on: well-being. All of these .;lliect and indirect effects are considered here as
effects on public health and welfare. It is important to note, however, the distinction between
voluntary and involuntary exposures. Exposures to high levels of environmental noise are
often produced. or .so:ught by the individ~aL .For example1 voluntary exposures to loud music
are common. Consequently, the concept of total individual noise dose with regard tb annoy-
ance, must be applied only to involuntary exposure, although, of course, this argument does
not apply to the effects.of noise on hearing.
A further consideration is the physical setting in which the exposure takes place.
Although there a.r; no data to j~stify the assumption, it isjudged here that, whereas a small
amount of speech interfe~ence' m:: most outdoor places:' is not detrimental to public health
arid welfare, the satne is not true for most indoor environments. Bas.ed on this reasoning, . ,
adequate protection of the public against involuntary exposure to environmental noise
· requires spedafconsideration of physicill setting and the communication needs associated
with each.
In the next subsection, the above rationale is applied to identify the maximum
noise level consistent with an adequate margin of safety for the general classes of sound .
. found most often in the environment Certain special classes of sound, such. a!i-infrasound,
ultrasound, and impulsive sounds are discL:;sed in the fmal subsection.
17
·· ..
. ----~--:---
IDENTIF1CATION OF MAXTh:IUM ExPoSURE.LEVELSTO AVOID SIGNIFICANT
AriVERSE.EFFECI'S . . . .. ..,_. ..
--:: : ·:": ... • ... --: :_ ... : .. ~. -.:. -. . . : ." -.-~ · .. · -~ ···:·' ..... : '. ~ ., ·. -.-, ..
.-:.:., -,·
.···.···-:·'···'·
:.:,_ .:;._· . ~ ..
Hearing· ··. .. _ ......
BasiC: Considerafions · .. ;, ..
The, following· consi~e~tio~~. ~ve· bee~ applied in identifying'th~ environmental .
· noise levels requisite to protect the hearing of the general populatiori. For detailed derivation,
justificationandr¢.ferences~(see.App~dix.C)~ ·· · >. ".. .: ·.. · · •• ,.. • .. .
-~. ·-;-·. '" -~
· 1. The human ear, when damaged by ~oise, is typieaJly affected atth~4000 Hz
frequency f"IrSt, and, ·therefore,-thiS ftequen~y. can·. be considered _the ~o'st nnise7sensitive
·frequency. The· averaged frequencies-or·soo Hz, i:OOO·Hz and 2000 Hi:kvetraditionally
.been employed in hearing Conservation: criteria because .. of their importance to·. the hearing
.·of speech sounds. Since there is considerable eVidence·thatfrequencies.abO:V~~zooo Hz are
. critical to the understandirig of speeCh in lifelike. situations,. and Sfuce4000 Hz is • C;oruidered
the most sensitive frequency~ 4000 Hz has been selected ciS th~ rttost itnportailt frequency to .
·be proteCted in thiSii.ociimerit; ·· • .:._ · .:-··· •· · .. , . .. · · : ~-:~::::. · ·
·.;:.
2. . Changes in hearing level of less than's dB ~e generally not,COil~der~d .
noticeable or significant.
";·-·-..
. , . . . · 3; . As indmduals ·approachthe high ~d, ofthe di$txibution:an<ttheir·hearing
..... leyeiS are decreased,. they become less affected by no~. exposure. Tit. othei: :Wol'dS; tlie~e
. eomes:apointwhere one cannot be damaged by"s~unds·which·one canil.othear. . .
.. . . . · 4. ·. The. nofs~ level chosen protects agarnst hearing lo~· up to and mci.udin'g: the:
· · .. 96th· percentile of the population;. ranked acfOrding t!) decreasirtg ability to hear-at 4000 Hz.
Smce the percentiles beyond that point are also protected (see consideration number 3)} ..
-~ ·,: .,, '';. 'vmi:lally the entire popUlation isp~otected agamst fucurrillg m~r~than a S;dB n·oise~induced
permanent. tl:rreshe>ld shift (NIPTS}. ·
Explanation of Identified Level for· Hearing Loss
Taking into account the assum~tions and considerations mentioned above, the
8-hour exposure level which protects virtually the entire population from <sreater than 5 dB
NIPTS is 73 dB, (see Figure 3). Before this value of 73 dD for 8-hour exposures can bt:
applied to the environmental situation, however, certain correction or conversion factors
must be considered. These correction factors are:
18
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PERCENTAGE OF POPULATION
Figure 3 .. Percentage of Exposed Population That Will Incur No More Than 5 dB
NIPTS Shown as a.Function of Exposure Level. Population Ranked by
Decreasing Ability to Hear at 4000Hz. (See Appendix C for Rationale).
L Intermittency: allows the exposure level to be 5 dB higher. This correction
factor is required because most environmental noise is intermittent (not at a steady level,
but below 65 dBA more than 10% of any one-hour period) and intermittent noise has been
shown less damaging than continuous noise of the same Leq· This correction should normal-
ly be applied except in situations that do not meet this criterion for intermittency.
2. Correction to yearly dose (250 to 365 days): requires reduction of the
exposure level by 1.6 dB. All data used as the basis of Figure 3 come from occupational
exposures which are only 250 days~ per year, wher~as, this document must consider all365
days in a year. . .
3. Correction to twenty~four hour day: the identified level of 73 dB is based on
8~hour daily exposures; Conversion to a 24-hour period using the equal-energy rule requires
reduction.of this level by 5 dB .. This means that continuous sounds of a 24-hour duration
must be 5 dB less intense than higher level sounds of only 8 hours duration, with the remain-
ing 16 hours considered quiet ..
Using the above corrections and conversions implies that the average 8-hour
daily dose (based on a yearly average and assuming intermittent noise) should be no greater
19
than Leq(8) = 73+5-1.6 = 76.4 dB. Extending the duration to 24 hours would yield a value
of 71.4 dB. For continuous noise, this value would be 66.4 dB. However, since em-iron-
mental noise is intermittent, this level is below that which is considered necessary to protect
public health and welfare. In view of possible statistical errors in the basic data, it is con-
sidered reasonable, especially with respect to a margin of safety, to round down from 71.4
dB to 70 dB. Therefore, the level of intermittent noise identified here for purposes of pro-
tection against hearing loss is:
Leq(24) = 70 dB
(For explanation of the relationship between exposures of Leq(8) = 75 dB
· and Leq(24) = 70 dB, please see page 4.) ·
Adequate Margin of Safety
Section 5(a)(2), as stated previously, requires an adequate margin ofsafety. The
level identified to protect against hearing loss, is based on three margins of safety considera-
tions: ·
1. The level protects at the frequency where the ear is most sensitive ( 4,00tl Hz).
2. It protects virtually the whole population from exceeding 5 dB NIPTS.
3. It rounds off in the direction of hearing conservation (downward) to pro-
vide in part for uncertainties in analyzing the data.
Activity Interference/ Annoyance
· Basic Considerations
The levels of environmental noise which interfere with human activity (see Appen-
dix D for detailed dicussion) depend upon the activity and its contextual frame of reference;
i.e., they depend upon "def'med areas under various conditions". The effect of activity inter-
ference is often described in tenns of annoyance. However, various non-level related factors,
such as attitude towards the noise source and local conditions, may influence an individual's
reaction to activity interference's.
20
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The levels which interfere with listening to a desired sound, such as speech or
music, can be defmed in terms of the level of interfering sound required to mask the desired
sound. Such levels have been quantified for speech commwrication by directly measuring
the interference with speech intelligibility as a function of the level of the intruding sound,
relative to the level of the speech sounds.
The levels interfering with human activities which do not involve active listening
have not been as well quantified relative to the level of a desired sound. These relationships
are more complicated because interference caused by an intruding sound depends upon the
background level and the state of the human auditor; e.g., the degree of concentration when
endeavoring to accomplish a mental task, or the depth of sleep, etc. Fortunately, there is a
. . . . wealth of survey data on cornrnwrity reaction to environmental noise which, although sub-
.· ject to some shortcomings when taken alone, can be used to supplement .activity interference
· data, to identify noise levels requisite to protect public health and welfare. Thus, the levels .. ·
identified here prunarily reflect results of research on community reaction and speech mask-·
in g.
.....
·.• ._..
.···:=:"•"•
The leveiidentified for the protection of speech communication is an Leq of 45
dB within the home in order to provide. for 100% intelligibility of speech sounds. Allowing .
for the I 5 dB reduction in sound levei between outdoors. and indoors (which is an average
amount of sound atten~ation that assumes partly.,open windows), this level becomes an .· ...
outdoor Leq_··of 60· dB for resfdent:i~ are~s~ ·For o~tdcior voice communication, the outdoor
Leq of 60 dB·allows· normalconversation·at distances up to 2 meters with 95% sentence·
intelligibility. ·· .. ·· · · · · . . . ·· ·· · ·· · . . .. · . ·· . ·· . .·
.··:·
· Alth0ugh:s-pee¢h-~teneieriee has been Identified as the•primfu"Y ~i~~f~r~nce bf · · · ·
. .. .. . :no!se with htiniaA a:diviti~s and is ·one of the primary reasons for adverse community reactions '
to noise and·IOng-term.annoyance, the lQ dB nighttime weighting (and, hence; the termLdn)
.. iS appliedto.give.adequate we~lit toaUofthe:other adverse effects on activity interference .. ···
:For the saine'teasori,"a 5dB ina®i'rofsafety is applied to-'th'e icfentitled outdoorlevel. There-
ofo.re,:the: ou~door L~i~entifiedJe>r reside~tial areas i.s ·55 dB. (See Appendi~ E. fot,relation-: •
Ship.ofLe~1~~dn~t.<.; ... · ... -... ·.c· · ·· · : ·.: .. ·· ·
. .. :• The:·assoaated interior day~~'t: ~oundlevel·~ithfu a typicallioni~: ~ruch ~esult~: .. ·.
from outdoori: js, 15 'dB less,· or 40.:dB:du~:to the. attenoatio~. of the striicture •. The:.expected . .. .. · · ··
indoor daytime.leyel for a typicaLneighborhood which has· an; outdoor Ldn of 55 dB is
approximately 40-dB; whereas the.ilighttiiiie level is approximately 32 dB ·(see Figure A;.7)~
This latter valueis. cOnsistent with. the limited available sleep criteria D-S .· .. Additionally'
. . . . . .
·:·,.
21
·'·· ..
. ._· ~:· :. :.
.·.· .. .-..
. -.:. .... •:.;
.-· ... ··
..
···'··: ~ .' -~: .... : .
. ·o· .••. ·.:;·-···
......
these indoor levels of 40 dB duriilg-the day and approximately 32 dB.at nigll.t are consistent.
with the background levels-inside· the ho~e.which ·have'been' recomniend~ by a,coustical .·•. . ...
consultants as acceptable for many years, (see Tabl~· D"'ro):. · · . ·. . . . . · ·
. -. : . . . . . . -~ ··: . .:'
'· ·····:·;~:;;) ..
' · ·.·· · ·Identification ofa·1~velwhlCh iS·S•·dB :higher than the 55 dlti4~ntifietf' ~bove
. would sigcificantly_.fuerease the• seventy, of the a~ge com~uriity reaction, as·well as the
expected perce~tage of complaints and annoyartre .• Conversely, identification of a leyel 5 dB
lower than the 55 .dB· identified ·aoove'would reduce·ffie fudoof' i~vels-'re~tiitini from ~utd~or
noise well below the typical backgrouriddndpo~ (see·'table '3) and probably make little
change in annoyance since ~t levels below .the id~tified'levei~·individ:ual attit!lde and. life
style; as well-as localconditlons,,see.nl. tit:b~·ntore:.~t.factors #1-.CQntrolling~the .
. · '.'.: .. resultlllg niag¢tude ofannoyanee. or communitY reicti6n than ~-the: a~lu~ 111agnitude
.. of the: level of the intruding noise. ·= ., ·: ..• , · . •. .• . . · · · ·.-.' ·
Accordingly, Ldn of 45 dB indoors-and ofS5 dB-outdoors~ ~esidentiaili!eas
...... , . care-i1ientifiea'as the· maximum· levelS ~low whl9-ll no effects brt. publicoiieaJth and welfare--·'
·· · ·· ·. 0Ccur..-d~e.to iri:terfef~~~e.with speech Or-other.-~vi_ty .. The~ Ieyels_-.)yo~ also· .. ptq~Ct'the_ ..
· .. vast majority of. the population. under most conditions-a~st annoyance:, .. in··thb-absence: of
. fhtrQsive noises. with_ particularly aversive content. .. . . . . . .
:: .;.·.:..-.
·· ... · ...
. . .; ·· .. :-·'-~ . : : .....
· The o~tdoor envfroi'unental n0i5e lewiict~iltified iii Table J provides a 5 dB
margin of safety with respect to protecting speech communication; T.hisis·.considered
· desirable for the indoor situation to provide for homes with less than average· noise reduc-
tion or for persons speaking with less than average voice level. A higher margin Of safety
would be ineffective most of the time: due to normal indoor ac.tivity background levels.
. ,-;.-'
The 5 dB margin of safety is particularly desirable to protect the population
against long~ term annoyance with a higher probability than would be provided by the levels
protecting indoor and outdoor speech communication capability alone. The 5 dB margill
clearly shifts community response as well as subjective annoy:mce rating into the :::1ext lower
22
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Table 3
SUMMARY OF HUMAN EFFECTS IN TERMS OF SPEECH COMMUNICATION,
COMMUNITY REACTION; COMPLAINTS, ANNOYANCE AND
ATTITUDE TOWARDS AREA ASSOCIATED WITH AN OUTDOOR DAY/NIGHT
SOUND LEVEL OF 55 dB re 20 MICROPASCALS
TYPE OF EFFECT
Speech -Indoors
-Outdoors
Average Community Reaction
.· ...
Complaints
Annoyance
Attitudes Towards Area
MAGNITUDE OF EFFECT
100% sentence intelligibility (average) with a
5 dB margin of safety
100% sentence int~lligibility (averag~)at 0.35
meters
99% sentence intelligibility (average) at 1.0
meters
95% sentence intelligibility (average) at 3.5 ·
meters
None evident; 7 dB below level of sigrJticant
''complaints and threats of legal action" and
at least 16 dB below "vigorous action'' (atti~
tudes and other non-level related factors may
affect this.result) .
... 1% dependent on attitude and other non,.!evel.
related factors
17% dependent on attitude and other non-, .
· level related factqrs
Noise essentially the least importantof
various factors
(Derived from Appendix D)
.... -:: ...
23
., ... ·:·-··.·
'• ··>·.'
'.
. response· category than would be observed for tne. maximum level identjfied··W'ith respect to
. . .. . . speech comm.urucationalo~e: Accbrdfug to preseri·t ::~ta:. tillS margin cifsafety p~~tects the .
vast majority·of the .. population aga,in~t.Jong.;.termariri?Y.:a.P:.cellY"rio.iSe~:ltwould reduce
environmental noiSe to· a leveL where it is leastimpottantamong'ehv:lforunen.ta;l.faetOrs that
.. ·· .... :=~t::;~:~:~ri:::~:!!tt:t:is~h~~:t~~:~~~-~~~e~:.:~:::~:~~hat
·· appears not possibie at the pre~nt stat~'ofkriowl~ge~ · .· · .. · ··· · · ·. ··· · ·
.... ···: · .. ·.: ... · .. ····· . '' ---~ ·:' .. · ...
·:····· .. :
. . . .
MAXIMUM EXPOSURES TO SPECIAL NOISES.
. .. _--'
•'. · .. ':;:~··: ·_ .. : ..... _:_ ..... ,.;••·---·· ... _ .. -.::-:
.····
· : ... ,~ .-~udible:Sounds··
.i,.·
Thefoll0wings6unds.may occiiioccasionally.bufare rareiyfourid'atle\te!S'highenough
to warrant consideration· in most environments :which· the public occupi~~ For a 1no:re ·detailed
dis.cu~sion,'seeAppendix G. · · · ' .• · · · · . . · · • · ·.
•' ., . --~
. _,,,.;·-.
. ·. ;-,; ··. ~-..•
IDfrasound . ·,:-
Frequencies below 16 Hz are referred to as infrasonic frequencies and. are not
audible~ Complaints associated with extremely.high levels·ofinfrasound can resemble a mild
· · · stress:r¢action:and··bi2:arre·auditory·sensations, such. as-pulsating and flu:tterii:lg; Exposure to
· · · · '· . high levelS·of infrnsound is tare -for most individualS'; Nevertheless, oii the b:.tSis' of existing
data2;7-, the threshold of these effects·is·approxin'lately 120-dB SPL (l-l6Jfz). Since little··
information exists.withrespectto-duratiOJ1s>fexposure-.and·its~ffe<;ts,and-alsosin~e.mal1Y
of the data are derived from research in which audible fi'e(fuencles w~e·-pt~serit fu· ~orne .
ampunt; these. results should· be interpreted :with caution.. ·, .·. ·
.. : .. ···· ·. . . . . ... ··.· •,. . . ,•
...... ;."·· ... ·.-.;· .. ·: :_·:-:'·''·
Ultrasound .· ·.·:·.····:··
. .
Ultrasonic frequencies· are those above 2_(l,OOO Hi and are also generaUyinaudible.
The effects of exposure to high intensity ultrasound iS reported by some to be a general
· · .· stress response. Exposure to high levels of ultrasound does not occur frequently. The thres-
. -~· hold of any effects for ultrasound iS 105 dB SPL 2·.,A.gain, many ofthesedata may include
· · frequencies within the audible range, and reSults are, therefore,to be interpreted cautiously.
24
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Impulse Noise
It is difficult to identify a single-number limit requisite to protect against adverse effects
from impulse noise because it is essential to take into account the circumstances of exposure,
the type of impulse, the effective duration, and the number of daily exposures, (see AppendiX
G).
Hearing
Re~ew of temporary threshold shift data leads to the conclusion that the impulse . . .. . ...
noise Iimitrequisiteto· prevent morethan.a 5 dB permanent hearing loss at 4000-Hz·after l 0 ...
·· _years of daily· exposure is a peak sound pressure level (SPL) of145 dB. This level applies in · · · · ·· • '·' '•
· ··· . · ... the ca5e of iS'(>Iated e'vents, imispective ofthe type, duration, or·incidence at the ear. How-.. ·
·· ever; for duration of25 microseconds. or less, a peak.level of 167 dB SPLwould produce.the-·
. same effect, (see Figure 4) .
... :.-··
.. 1. . Dmtion Correction: When the duration of the impulse is lessthan 25 ~icr-0-·
: seconds, no correction.for duration is necessary. For durations exceeding25 microseconds,
the level should be;reduced.inaccordance with the "modified CHABA limit" shown in·
Fig-.ue 4 and Figure G-1 of AppendiX G.
2. Corredion for Number of Impulses:
·····:
. N ~ber of impulses
per day: 1 10 100 103 104
· Correction factor: 0•· -10 ~20 -30 40·. dB
. (More detailed infomuition is provided in Figure 4.)
Furthemio:re, if the average il1tervarbetween r~peated impulses is between 1
and 1 0 seconds,· a third. correction factor of -5. dB .is·.applied:. Thus, to prevent hearing: loss
due to impulse noise.,' the identified .level is ·145 dB SPL, or l67.dB peak SPL for impulses
less than 25 microsec011ds, for one impulse ·daily. For longer durations or mOre frequent
exposures, the eql#Valent levels are as sliown in Figure 4.
······.
25
· .. ··· ..
,--_-: ..
:··,
,;
·::--:
/
.. : ~--.
. ·:·· :~-:-...... ~-~--·· ~-,.-.. _ ' ... . : . .-.: . --~'-..-,
0.025 0.05 0.1 0.2 0.5 1 . 2 5 10 20 50 100 200 500 1 000
Figure 4.
B'-DURATION (ms) . . : . ., .
Set of Modified CHABA Limits tor Datiy cA.!Ju:o.wc tu lmpU!se Noises
Having B•Durations in the Range 25M .. "'''osecondsto 1 Secoriq. (Para-
meter: number (N) of impulses per daily exposure. Criterion: NIPTS
not to exceed 5 dB at 4 kHz in more than 10% 9f people.)
(Derived from Appendi;: G)
26
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Non-Auditory Effects of Impulsive Sound
Impulses exceeding the background noise by more than about 10 dB are potentially
startling or sleep,.disturbing. If repeated, impulsive noises can be disturbing to some individuals
if heard at all(they may be at levels below the average noise levels). However, no threshold
level can be identified at this time;nor is there any clear evidence or documentation.of any
permanent effect on public health and welfare.
Sonic Booms
Little or no public annoyance is expected to result from one sonic boom during
the daytime below the level of 35.91 pascals (<Y. 75 pounds per square foot) as measured ·on
the ground (see Appendix G). The same. low probability of annoyance is expected to occtir
for more than one boom per day if the peak level of each boom is no greater than:
. . ,. . . ~ . . . . P~ak L~v~I =· 35 ·91
. · ...rN'· .pascals
'Where N is the·-~~ber ~iboo~s.This,~ue:is ~ ag!ee~~iit~th the equai ener~ concept
... ;. ·.:.-·. :.;:-.... ·
·.· .
.. , ·-·~:: ..
;-: ... ·
.··.·
· .. :·.
. ·.·::·. ..· ..•. · .
····-·· .. ·· .. ·. · ..... .
. :'·
·· ... ···· .. ···
27
·-----·
. , .. · .. · ...
.•. : '.: ~" .' .,.· .. ·.
... ; ·. ·-~ ·.. .
.. ···------
·--:'.
........ ·· ... _.,
··::' . . •:'
-... _ .. __ ·...;·:::.
: ~. . . . . . ' . . .. ,,
.. .. -~ .. ·. ; .... _.· .. -..
-":<··
:' ;. sedi.o-n4 ... . . ·-·::.:, -.. . . ·.~ ... ·. ;_-.; · .. ··· .... ···.· ·:: ..
ID·ENTIFIED· LEVElS OEENVIRONMENTALNOISE IN.DEFINED:AREAS . . . . .. . . •'• ...... · .. ·.·.·"''
··· ..... :·.-. ·---: .... _ . .-...
._ ... , ..... : _.··.-.. ,. ··-:-·-: .. "' . . ~ ........ .
·.,·.IDENTIFIED·LEVELS .. .. ;.·-.:· .. · .··
.-.:·
Table 4 identifies the level~ .reqtmi-te -to protec~ .pu~UC. .b~a1th artd::\Y.·ejrar_~.:_-W:ith:~~ · ade-·: ·---· .. · · ··-
quate:margm of safety·'for both activitY inteiference .. and hearinlloss:; The table<c;la!!Sifies the
various areas according to the primary :activities that are-.rnosHik~Iy i<l:o.cbllt:iri·eacli. The::··· : .. ·. ··'
following is· a brie(description,.of each cla~sificatiqn.•and,a diScuSSjoJt;(lf the baSis fot the.
identified.levelsin Table 4. Fora more'detailed ~s~ussion.of:hearingl()ss;;m~'ac~ivi~y inter·
·· ference, see Appendices C and D. .· .. · . . · . . .
. .
I. Residential areas are areas where human l)emgs frve.;.m<:Iuciing apartments; ~sonal· · .. ·
. residences, and mobile homes, ~weU asyear~rolind'residen~;A quieterl.Vi!toili)letjfis ·
necessary in both urban and rural residential areas in order to prevent,:actiVity interf~rehcd . ·
arid annoyance, and to permit the hearing mechanism to recnperate ffit ~·~xpbsed to higher .
levels of noise during other periods of the day. . ·. · · · .·· . · .
An indoor Ldn of 45 dB will pernut speech·'communitation .fri·:the hortie,·while an '·' ·
outdoor Ldn not exceeding 55 dB willpermit normal··speechcommw)i~tion'at.app;roxi-...
mate'lythree meterS. Maintenance. ofthis identified outdoor 1eve1willproVi(i·e·an:W,~oor
Lctn of approximately 40 dB with windows partlY open for ventiliition:·The ·nighttime por~
tion of this Ldn will be approximately 32 dB, which shouldin most cases, protect against·;
sleep interference. An Leq(24J of 7adB is identified as ~otecf.ing·ag~~~age ~oheanrig;
. . ' . ' . . . . .,_ . . . . ~-. '. . . . . . ' ; . . . . .. · . . ... ....
.. Although' there is a sep~ate category for coinmerci~tareas,.co.!rim.~ciallirlng .
accommodations such .as hotels, motels; cottages, and inns should be inclUded in·the resi~
dentialcategory since these are places where· people sleep and sometimeS spend extended
periods of time.
....... ,
2. Commercial areas include retail and lmancial service facilities, offices, and mis-
cellaneous commercial services. They do not include warehouses, manufacturing plants,
and other industrial facilities, which are included in the industrial classification. Although
a level for activity inteiference has not been identified here (see footnote a}; suggestions
for such k.vels will be found in Table D-10 of Appendix D. On the other hand, a level of
Leq(24) of 70 dB has been identified to· protect against hearing loss.
28
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Table 4
YEARLY AVERAGE* EQUIVALENT SOUND LEVELS IDENTIFIED AS
REQUISITE TO PROTECT THE PUBLIC HEALTH AND WELFARE WITH
AN ADEQUATE MARGIN OF SAFETY
Indoor
Activity Hearing Loss
To Protect Outdoor To Protect
Activity Hearing Loss
Measure Inter-Considera-Against 'Against
Both Ef-Inter-Considera-Both Ef-
ference· tion ference tion fects (b) fects (b)
Residential with Out· Ldn 45
side Space and Farm
Residences Leq(24)
Residential with No Ldn 45
Outside Space
Leq(24)
Commercial • Leq(24) -(a).
Inside Tr.msportation Leq(24) (a)
Industrial-'. Leq(24)(d) (a)
_Hospitals
. ; ::.: ~
45
Educational" -Leq(24) 45
: Leq{i4)(d)-
(a)
Farm Lai1d ancC --r,;eq(f4)
· Generalll!ipopulitted ··
.:• ···.· ..
Land ,, . ~ : •.·: ..... . '.:··
45 55 55
70 70
45
70
'70 70(c) 70 · 70( c)
70-(a)
70 70(c) (a) 10 70(c)
45 55 ·s5
70 70
45 55 55
-·-·-70 :7o
;·.· ...
70 70(c) (a) 70 · 70(c.)
(a) 70 70(c)
a.. Since. different types of ac_tivities.app~ar to b~: associated-with -different levels·, identifi~ · ·• .
. cation of a inaximtim level for activity interference may be_ difficult' except in those .
. .. · ·Circums:tances where:speech oommunication is a critical· activity. (See Figure -o~z·far
noise .levels as a function of distance -which allow·: satisfactory communication.f · · · -
·b. · Based·_on lowest level. ·
c. Based only on hearing loss. . .
d •... An. 4q(-8} of 75 dB. may· be identified in these situations· so .long as the. exposure-over:.
.... -,, the 'reimiining 16 hours-per day is low:enough.to result in a negligible contribution to
· the2fh-ouraverage,b~ .• no.gre:iter than an Leq.of60dB.: --_,_ _ ·
._ . ; ·N'ote: ., .. ; E~~ian~tion-~f ide~tified·fe~~~ T~rhearirtg lei~~ The e~~osu~e ~eriod whkh
... r.esults-in he:~ring·loss at .the identified ,Jevel is a ·period,of 40 years.·. · ·
*RefL"rs to eJieriw rather than·arithmetic aver&ges~
... · .. ·
29
..
.. ;·,
.:·',·.· ...
.. :;··.:, .. ···:·.; .. ··
... ; ' ~· ...
·· .... .. ·.
.· .. ;:
. . ·' .. : ... :;·; ... . ·:, .·
3. Transportation f~cilities are included so as to protect in{jividuals using public and
. private transportation .. Included within thiS-clasSification are commercial and ptivite trans•
· portation vehicles. Identification· of a' level to prot~ct,against hearln8:·J9ss.is'th:e: o.nly criterion
. U$ed· at this time; although ~velsJO'Nef;than :an. Leq;O{;,]Q:d'B ate oft¢Ji ·~eSita'bl~'fo'feffective '
: speeCh communication~ However,. because ot'the gr.eat:variety. .of :coJi<fitions·iri$id'e' :transpor-·
. ·. tation vehic::les, and' because•of the desirability of·speech:priyacy~ c¢t:i~·-Sit~~tioris,.a-leyel :·
· .. based on activity interfer~nce cannotbe'identi:&d for all'JI1()de.sof t~swrtafu'n''at.this ...
time~ >.. ' ,.. ... · ... ,· .. ·;:. · •: ··· .· .:·,·-'· :·.'·
··•·• · ... · .· .. : ·:·. :. :. ~· . : ...... ! .. '· ·. . :_.:. ·; ... :~<:; -~·.,:,. ••.
.. :.· :·;·····.' .··. : ; ... .":: · .
.. ' : 4. Industrial areas include such·;fdties'as mzmUf~numgplailt~rw~~h~~~~~ storage: .
. areas, distribution facilities, and· nilillng ·operations~ ·only· ·a· kvel"for hearin-g ·los~: :k identified ... :
· due to the lack of data with respect to. annoyance and activity interferenCe~-Where, the noiSe
.. . .. .... ·: .,_ exposure is-intermittent, anLeq(24)·of.7.0 dB is identified as the, inax#umJevef(orJ)rote~~-··
·.· : ··tion of hearing from industrial exposure to intermittent noise. For 8•hour expasures; an
Leq(8) of 75 dB is considered appropriateso long as_the exposure oVe~ t~e remaining.16 .
hours per·day is low enough to result in a negligible contribution to the· 24haur:ave~ge. ·
.... •· .· 5~ . Hospitahreas in.clude the immediate neighborhood Of the hQ~R~tar as w_ell as its ...... ·.
futeiior. A quiet envirorunent is•requited'in hospital·areasbe~use ofthtfihipottart~of sleep ·
and adequate· rest'to the reoover-y of patients. The maintenance of a noise level not exceed-
ing an Ldn of 45 dB in the indoor hospital enVironment is deemed ade.quate to pr~vent activ-
ity interferenee and annoyance. Art outdoor Ldn of'S'5 dB ·should be' adequate to protect
patients who spend some time outside; as well as insuring an adequately protective indoor
. levet A.It Leq(24l of 70 dB.is identified to P.~event hearingloss.i ,. . · :,,:~:-;" ., • ·. ; ·
. 6. . Edllcational areas include ClassroomS,. auditoriums; schools in· gene tat; ~d. those
.. gro:unds•nqfused for athletics. l'he principaLeonSideration iri _the· edUtaJiol1 :eP.y.ircntment is .
'.· ...... :. _; ' the preven-tion of interference ~ith activities; particularly speech ccimriiimici:tibft~ An indoor
........ ·• .· . noise levelp.otexc~.ediftg Leq04} of 4S. ~B i5 id~ntif:1ed a~ acl.ecJ,~te_t9 {~~ta,te. ~~9~~htand: ·
.. · cqmmunication. Since'teaching is·occasioJ:.IallY conducted'outsid.e the'cias5room~ .an p!ltdoor-·
·· · ··Leq(24yof55 dB is identifiedas the maxiniundevetto pre~~nfaCtivitY•lP:tefference~·To pro~· --
. , teet against hearing .loss an Leq(24)0f 70 dB is. identified fer both indoof"~d. out~o<:>r
. environments. As in the industrial situation, eight hours iS generally the· amount 0.f time
spent in educational facilities. Therefore an Leq(8) of 7 5 dB is considered· appropriate to
protect against hearing loss, so long as the exposure over the remaining 16 hour-s is low
enough to result in a negligible contribution to the 24-hour average.
7. Recreational areas include facilities where noise exposure is voluntary. Included
within this classific::ati<:>n are nightclubs, theaters, stadiUms, racetracks, beaches, amusement
parks; and athletic fields. Since sound exposure in such areas is usually voluntary, there is
seldom any interference with the desired activity. Consequently, the chief consideration is
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the protection of hearing. An Leq(24) of 70 dB is therefore identified for intermittent noise
in order to prevent hearing damage.
8~ Farm and general unpopulated land primarily includes agricultural property used
for the production of crops or livestock. For such areas, the primary considerations are the
protection of human hearing and the prevention of adverse effects on domestic and wild
animals. Protection of hearing requires that an individual's exposure to intermittent noise
does not exceed Leq(24) of 70 dB. A separate level for the exposure of animals is not identi-
fied due to the lack of data indicating that hearing damage risk for animals is substantially
different from that of humans. The unpopulated areas include wilderness areas, parks, game
_ r~fuges, and other areas that are set aside to provide enjoyment of the outdoors; Although
qUiet is not always of paramount importance in such areas, many individualS enjoy the ..
special qualities of serenity and tranquility found in natural areas. At this time it is hot
possible to identify an appropriate level to prevent activity interference and annoyance.
However,whenit becomes possible to set such.a level, a clear distinction should bemade
between natural and man-made n()ise.
:· .·.·.
:..·· ..
USE OF IDENTIFIED ENVIRONMENTAL NOISE LEVELS .
..; ···'. .. . .. ··· ..
One of the purposes of this document is to provide a basis for judgment by ~tates and
local governments as a basis for setting standards. In doing so the information contained in
this document must be utilized along with other relevant factors. These factors include the
balance between costs and benefits. associated with setting standards at particular noise
levels; the nature ofthe existing or projected noise· problems in any particular area, the
local aspirations _and the: means available to control envir_onmental noise.
In order to bring: these. f~tors.toge.ther, states, local governments and the public will
need to evaluate ina;systematic manner the following:
.. : ·:.-:::.:·:·:··: .' .' :~
1. ·. The.magnitud~of e-XiSting or proje~ted.rioise environments m deruied areas as
compared with ~h~. various le~els· ideritifi~d in_ this. document .. · · · · · · · ·
.. 2. . The cOmm~ty expectations fo~ noise abatett1ent with respect to existing or
vrojected c()hditions. . .
.. :·:: ..... 3. . . ·Tlie.atfected' elem~rit~:~f.th~:_:pub~c imd'th~·-d~~~e:~ik'pact oi'~t~~~t-,~~ pro-
jected envirQnniental.noise levels~' .·· ....... --,-···:• : . · · .. · · '· .-,. · ·
· 4. The noise sources, nof controlled: by Fedei:alregUlatlons, that-causelocal noise
problems. ' · -' · · · ·
,·.:
31
~-'.:= . -~ ..
5~ Methods available to· attack .. enviroruriental noise problems (use llinitatio~,:sotiice .
_control thr~ugh noise emission standards, compatj.ble land,use plamlil1g, etc.).
.· .. ,..
6. The 'costs inherent i.ri reducing noise to certairi: levelS and benefitS:a~hleved· by ' .· . . . . . : . . . . . . . ' . . . . ·~ , .. ·. .. . ....
.. doing~. . . . ···· · ···· · · .. :. . :: .. :.·.·: ·,-· '' ....
····· .;·.. ·_;., ...
. . . 7. . The availability of techhol~gy to achieye ,the desiJ::ed noise·ie9;\.1Cti:()n; :, .; .... .. .. . .. . ,,_ .· .;,_-: ...... ;. .. ........ . .. ; . . . . .
··.··· ... •.··.'·· '.' .· ;., .
The levels ofenvironmental:.noise identified ill:this ·report proVide:the·b:asis·fa.T~asse~g' •-· ·
·. the effectiveness of any noise.abatemel;lt program..These,noise.levels are-iderttified:irrespecti.¥e· . · .
.. ·, .. ,_ of the na,ture P.fflllY individuatnoise.~~our~. One oftheprimaey purposes.·ofldentifying.·:~::: .. ;·: .. ;:· ·.: •
environmental ~oise levels is to provide .a b'asis by which noise· source emission regulations~ . ·
. . · .. · human exposure $lldards,.land. uSe.. ptalming, zo:rling, .and· building codes may.be asses~d; .. ·
. as to the' de~ee with which they protect the public .health. and· welfare· with-.-tespect:to nOise;' .
Such regulatory action must consider ~eciliitical f~bili_ty ~d econOmic reasonablenessithe.
seale of time over which results can be.:expectedi ilncf the specific problems of enforcement ..
In the process--of balancing these··conflictiitg· elements; the'·puhlic health•and\velfare ·~~~~ · · ·
sequence· of .any specific decision can·· ·be detennined ·by comparing the• resultant n()ise ··
environment against the environmental noise levelS identified in this r~polt~ .
. ' . ; ~' ' ···.
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32
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REFERENCES
1. Noise Control Act of 1972, Public Law92-574, 92 Congress, HR 11021, October 27, ·
1972.
2. Public Health and Welfare Criteria for Noise, EPA; July 27, 1973, 550/9-73-002.
3. "Report to the President and Congress on NoiSe," EPA, NRC SOOJ, December 31,
197L·· · ·'·· ··.· · · . ,.,., .. ···
. .. . .
. · .. . 4. ''Impact Characterization of Noise Including Implications of Identifying and· Achieving
Levels of Cunnilative NoiSe ExpoStire,'' EPA Report NTID 73.4, 1973.
5. Proceedings of the Conference on Noise as a Public Health Problem, EPA Report · · ··
550/9-73..008, 1973.
. 6.. · Seacoi:d, o:F~,.!. AcotisticalSociety of America, 12: 183; 1940.
7. Johnson, I)~, "Various Aspects of infrasound," presented at the Colloquin on Infra-
sound, Centre Nationalde la Recherche Scientifique Paris, September 1973.
... ·
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GLOSSARY
AUDIBLE RANGE (OF FREQUENCY) (AUDIO-FREQUENCY RANGE). The frequency
range 16 Hz to 20,000 Hz (20 kHz). Note: This is conventionally taken to be the
normal frequency range of human hearing.
AUDIOMETER. An instrument for measuring the_threshold or sensitivity of nearing.
........ : . AUDIOME.'JRY~ . The measurem~nt of hearing .
. ~l~.OAD-BAND NOISE. Noise whose energy is distributed ave~ a broad range of frequency
--~---~~~c-c:c::-:,----:.(gener-ally~spealcing-.:-rnore-t-tum one octave).
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CONTINUQ_U~N91SE .. ·Ori-gomgnoise:wh.oseiritensitytemaipsat a measurable level·
(whichli1aY.YC:U"Y)Withoutinterruption over an.indeimite period or a spe.cified
period <)f time.:· ·
DEAFNESS .. 100 percent impairment ofhearing associated· with an organic-condition.
· Note: .This is .deimedfor:medical.and cognate purposes as the hearing threshold
. leveFfor.sp~~h <;>r the_ average,h.earing .thresholdJevel.for pure, tones of 5·00,·1 000 ·
aiid-:2000 Hz· in excess of92 dB. ·•· ·· .. . · .. ·-. .-.·.
EQUIVALENT SOUNI) LEVEL. The level of a constant sound which, in a given situation
and time. period, has the. same sound energy as does a time,.varying sound. Techni-
cally, equivalent sound level is the'fevel of the time-weighted, mean square,,._.·
A-weighted solind pressure. The time intervat:O.ver whi~h the· measurement is .....
taken should' alWays be specified.' .,_. ... · ,.. · · ·· · ·· · ., .. _· ··
....... -. ~ ": .. : ' .. ··.· : .... , , ' ..
···ENVIRONMENTAL NOISE: ··ay.Se~ 3(11)-ofthe.rqoise Control Act ofl972,the term
"environmental noise;1 means:the.iflteriSity';·drirati~tl', and chara~ter:of soundS .
· from all.sour~s.
HEARING LEVEL •. The differen~ in sound pressure level between _the thresholci sound
. . .. for·a persorf(or the median.:vaiue or the aveia:ge.for ~ ~o~p) arid. the ref~r~:;{~e
sound ·pressure level defming the ASA standard audiometric threshold (ASA: 1951). ·
Note: The term is now commonly used to mean hearing threshold.level (qv).
Units: decibels.
Glossary-1·
~-..
.:": ..
. · ... ,.,.
·····HEARING LOSS. hnpairnient of auditory sensitivity: ·~· ~ievatiori: ofa·h~g threShold
level. ·· · ''· · ......... ·:· ............. .
: ... · . . . . . ' ; : ... ;· .. ··~'~: ~: -:;:;·.: ... ~:· ... :· ... : : ..
·'·HEARING THREsHOLD·LEVEL the. amount by whl~h,the·:thfeshbld:b(ll.eanng for an
. . . ear .(or the.average for a gfouil)~ exceeds tb.~ s~an~d .audiomemc:·refe~.ence· zero .
··(ISO 1964 ·ANSI 1969) · .t.Inits · · decibelS · ... · · · ,. · .· .. ·.·... ·. ··.·• .... ::·:~··~; ·/: ~· .. · . ,. . . .; .. ,.. ~-......... · ... · ..... ·. · ... •; ~-.. :. ·-· .. ; ··:-.. . . ·,-.... " '
. -· . IMPULSE NOISE. (IMPULSIVE·.NoisE). No~e ~;:~~~~:·a~i~9n .(;;;~~~:~:·;han o~~
: '. . . ·second) especially of:high·intensity, abrupt onSet and ra:pid' decay~ and: often
. ... rapidly changing spectral' composition.:-Note: ··IriiP.ul8e' noise . .-is:~~~P.te'ristically· , . ·
associated with such somces as explosions, impacts, the• discharge of;frrearms, the
pas~ge of ruper-sonjc aircraft (sonic boom}·and ~a,ny industrlah,roce5ses. .. ·
0 0 ••, • 0 ° O -~· •• p ·., .·.'
00
° '• • ,:~' :_., : • ... ·:.•.,:,:. -~: •• • 0000 ""!"':i'• oA'.:.:", • ",• •::::·.·.-.:~-.·~. •'·.·,',:.-,•
INFRASONIC; . Having a frequency below the audible' rang~ for man (dusto~api; deemed .
· ··.· .. ·. · .. _t9-c~~ of! a-t -~6 H~). · .. ;~~----··= .. ··. .. ....... ;. · ..... ,_ -=<--;.. .·'·:r·t::·'·:):'.,:···:
.INTERMmENT NOISE. Fluctuating noise whose le~l falls .once or more times to low or
unmeasurable villues during an exposure; In thiS doct:lment:itltemuttent'noise will
mean noise· that is below· 65 dJ~A at leastJ:O% Qfany 1 hour·pe~ba.::· · ' :: :
. . . . . . . . . . ·• . . . . ~-.. · . . ' . . . .. ··.. ' . .-; . . . .
NOISE EXPOSURE. The cumulative acoustic stimulation reachi:iigtll~eat'ofthe person
over a specified period of time (e.g., a work shift,.a day; a· wdrking.life, or a lifetime) .
. _,..·
NOISE HAZARD (HAZARDOUS NOISE) .. Acoustic stirhui~tion cif:tli~:~·which'~:likely .
· to produce·noise"'indu~d permanent thresht;>:ld:;shlftin:'som~·of:~.:'p.QpUlatio.n;
·· .. ··.:· .. ·· .·.·.-: ....
. :· .
NOISE-INDUCED TEMPQRARY·TH~SHOLD SHIFT. (NITrS) •.. T~paT.ary"threshold ·
shift caused by noise exposure.
· ·, NON-VOLUNTARY EXPOSURE TO ENVIRONMENTAL NOISE. The exposure ofan
indiVidual to sound which ( l) the individual cannot avoid or (2)the sound serves
no useful purpose (e.g., the exposure to traffic noise or exposure to nois·e from a
. lawn mower).
. . . . . . . . . . . '
OCCuPATIONAL EXPOSURE TO ENVIRONMENTAL NOISE. The noise exposure of
an individual defined under P.L. 91-596, Occupational Safety and Health Act of
1970.
Glossary-2
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OTOLOGICALLY NOR.J.\1AL. Enjoying normal health and freedom from all clinical mani-
festations and history of ear disease or injury; and having a patent (wax-free)
external auditory meatus.
PEAK SOUND PRESSURE .. The absolute maximum value (magnitude) of the instantaneous
sound pressure occurring in a specified period of time.
PRESBYACUSIS (PRESBYCUSIS). Hearing loss, chiefly involving the higher audiometric
frequencies above 3000 Hz, ascribed to advancing age.
RISK. That percentage of a population whose hearing level, as a.result of a ·given influence,
exceeds the sp¢cified value~ minus· that percentage whose hearing level would have .
exceeded, the specified value in the absence of that influence, other factors r.emain-
· .. ing the same. Note: The influence may be noise, age, disease, or a combination of
factors. ·
SOUND LEVEL; The quantity in decibels measured by a sound level meter satisfying the
requirements of American National Standards Specification for. Sound I.;evel Meters
Sl.4-4971. Sound level is the frequ.ency-weighted sound pressure level obtained ....
with .the·standardized dyllamic characteristic ·~fast" or "'sl.ow" and weightillg A, B, .
or c; unless indicated otb.erwise, the A-weighting is understood. The unit of any sound
.level is the decibel, having the unit symbol dB.
SOUND EXPOSURE LEVEL. The .levelof sound accumulated·over a given· time interv<il
or event. Technically, the :sound exposure level-is. theJevel of the time·hitegrated
mean square &weighted.sourid.for. a stated time interval or event, .with.a.refere.nce
time of one second. · · ·· . · .
. ·•·,
SOUND PRESSURE "LEVEL. in de.cibel.S~ .. 20 timesthe logarithm to the base te.n of the
ratio of a sound pressUre to the refe~ence sound pressure of 20 micropascals (20
micronewtons .Per square .. meter) .. In the absen~e of any .. modifier; theJevelis ·
understood to bethai·ora·mean-square pres5ure; · · ' · .·
··SPEECH DISCRIMINATION. The.ability·to distinguish:and understand speech signals •.
... :.~
. ,._...,_ ., .. -. ····:··:·'· · .
. TEMPORARY THRESHOLD SHIFT {ITS:). That com'pOilerit of threshold' shift which
·· ·· · ·. ·· · Sh<?.Ws a progr~sive red~ction with the passage of time after th~ apparent cause ·has·, .
been removed.
:.· ...
.... _. ;.
THRESHOLD OF HEARING (AUDffiiUTY). The minimum effective soun4 pressure level .
of an acoustic signal capable or·excitfug the sensatiori "of hearinght a specified propor-.
tion of trials-in prescribed'·conditioris ofli.Stening:c··' ,,. · .· · : >:·:·' ··· · ·· .... ··
:. . :•.. .· .-· ... ,
·.· ULTRASONIC~ ·HaVing a frequen~y,above the a~dible,Iarige.f6r·man (~6~~~ti~ri~y·
deemed to-cut off at ·2o;oooJu);::.:. ,., ..... · . . ... ; ~-: ,,.,:: .. ":;.
··::;.::_. .... ... : ..... ·.-•>-: .,:_.,: ... _ .. •
., __ , __ .. ·. ·.:.,_._._ •.:··,._ -.. · ... ·.-.:·--··
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Glossary-4
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·APPENDIX A
EQUIVALENT SOUND LEVEL AND ITS RELATIONSHIP
. TO OTHER NOISE MEASURES . -
. -.. -:' ... ;
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Appendix A
EQUIVALENT SOUND LEVEL AND ITS RELATIONSHIP
TO OTHER NOISE MEASURES
DEVELOPMENT OF EQUIVALENT SOuND LEVEL
The aCC:umwated ·evidence of research on human response to sound indicates clearly
that the, magrutude of sound as a function of frequency and time are basic indicators of · ·
·human response to sound. These factors are reviewed here, and it is concludedthat it is not
necessary to invent. a new conc~pt for the purpose' of identifying levels of environmental
noise.
1.\llagnitude
Sound is a pressure fluctuation in the air; the magnitude of the sound describes the
physical sound in the itir; (loudneSS; on the other hand, refers to how people judge the
sound when they hear· it). Magilitude is stated in terms of the amplitude of the pressure
fluctuation. The t"allge of magnitude. between the faintest. audible sound arid the loudest .
sound thee'~ can With~tand is so enormous (a ratio of about 1 ,000;000 to 1) that it would' ...
be very awkward. to express sound pressure fluctuations directly in pressure units. lnstea'd; ··
this range is. ''~mpressed" by expressing the sound pressure on a logarithmic scale. Thus,
. sound is described ffi.terrns ofthe sound pressure level (SPL), which is ten times the com-
mon logarithm ofthe··ratio ofthe squaie 'ofthe soUrid.pressure·in question to the square
· of a (stated or·unde~tood) reference sound pressure, almost always 20 micro-pascals.* Or, ·
j!l: mathematical; terms; so~nd .. pres8urelevel I;.e'xi>~~ssed. in decibels is:. . . . .: . • ..•..
. . · ... :.~~·.p2
L =· JO,log; .... 2 .
... . .Po ·
... : (Eg~ A·l) . ... ·:--·
.. \Vher:e p iS·~thepte~ure.fltictuatiori.and Po iS the r~feience·pressure.
. . . ·· .. ·. ·. ·-::· .. · .. :: ... . . _.: .·. . .. ·· .. ··:. ._,.-. :··::·: ... ; ·· .... .······· : .. ;: ,; .· .. ·.:··
... ···
··'.•, ..
*One pascal= one.newton per square meter.
... ; ~-_ ....
.. Frequency Characteristics of Noise .. . : . . ~ '. ...... ~ ... . . ... _ ':-....
The response of human beings to sound· depenc!s. sqongly on:· the frequency of sound .. ·
In genera4 people·are less sensitive tO. sounds oflow freq\lency,,such as,.~:O.<f:hert'Z (Hz)*,
. than •to sounds at 1 000· Hz; also at. h.ig1J. frequencies. such ~.80001'Iz; sensitivitY" decreases.
.. · Two basic approach.e11.to compe.p.sat~ forJli.is·diffe~!lcem·re8pc:>nse todiff~rent·ftequencie5
. a:l:e (1) to segmerit"thesound pressure·s~ctrum ilttO.a.siriesotoontigu<>us;freqtiency bands
by electrica:l filterno as to display 'the· distribution 'of s~u:nd' energy ovei· theOri~-u~"ncy
. ·range; or (2) to apply aweighting·to•the:ove~all $l?.ectrum.in sUCh: a waytJ:lafthE;l SoUnds at
. ·various frequencies are: weighted· ill inuchthe .same wa:Y'.iiS' ~e:li~ ear . .liear~.~hem. • . . .... -. :-·--~ .. _;-. ... -;:... .. ··• . ....
· • · .·In the frrst approach a·sound iS segme~~ed ~to'sdun4 p~~~e· Ie~~k·h..i4.·different
frequency bands, which may be used to calculate an, estimate ofthe ''loudness'' or "noisi-
ness" sensation which the sound may be· ex~cted to cause.•.This· form .ofanalySiS.into bands
iS usually employed when detailed· engiiteenng studle8 of nciise: soitl-ces.are l'equfred·; It is
· .. much too·.complicate<i formonitonng:noise exposU:re:' ...• < :. ·' .. . ;,. ' ·' ·.:· ..
. . :•. . . . ~. -..
. · . To perform . such analy~,·especially.fo~ .. ~·varymg..SQ.Unds,..requires·a'·~very complex.
· .. set of equipment. Fortunately~ much ofthlS complication ean· be avoid~d by using approach
. 2, i.e., by the use of a special electriCal weighting:netwotk m. the meastir.emerit sys.teni. Thls
network weights the·contributions.of sounds .. of diffe~rtt freque~cy so·thatthe·response of
. ·the average human ear is simulated. Each frequency of the no~e then c9ntribu.tes iothe
total reading by an amount approximately proportiohal to ihe.subjective· response associated
with that frequency. Measurement of the overallnoisewi~a&ound levelm~t~rincorPorating
such a welghting network yields:~ single niunber, such as the A,..weighted·-Soimd•: Level, or
simply A-level, in decibels. For zoning and morutoring.purpo5es,.t}$ matks;an·enormous
.•·.·· simplification; For-thisreason,·theA~levelhasbeeri adOpted iri'latge.:Sdaie stifV~ys of.city
noise coming from a :variety of sources,; It is·widely accepted aS•an:adequa~e:way to deal
with the ear's differing sensitivity to sounds of different freq,1,1ency} im:ludfpg:~sment·of ..
· noise with respect to its potential for causing hearing loss. Despite the::faclti18_t mgre · ·.
detailed analysis is frequently requited for engirteering noise control, the resui~ •6i such.
noise control are adequately described by the simple measure of sound)eveL.
One difficUlty in the use of a weighted sound level is that psychoacoustic judgment
data indicate that effects of tonal components are·sometimes not adequately accounted
_ for by ·a simple sound level. Some current ratings attempt to correct for tonal components;
•Hertz is the international standard unit of frequency, until recently cailed cycles per second;
it refers to the r, ··mber of pressure fluctuations per second in the sound wave.
A'-2
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for example, in the present aircraft noise certification procedures, "Noise Standards: Air-
craft Type Certification," FAR Part 36, the presence of tones is identified by a complex
frequency analysis procedure. If the tones protrude above the adjacent random noise spec-
trum, a penalty is applied beyond the direct calculation of perceived noise level alone. How-
ever, the complexities involved in accounting for tones exceed practicable limits for monitor-
ing noise in the community or other defined areas. Consequently, EPA concludes that, where
appropriate, standards for new products will address the problem of tones in such a way that
manufacturers will be encouraged to minimize them and, thus, ultimately they will not be a
significant factor in environmental noise.
With respect to both simplicity and adequacy for characterizing human response, a
frequency-weighted sound level should be used for the evaluation of environmental noise.
Several frequency weightings have been proposed for general use in the assessment of response
•o noise, differing primarily in the way sounds at frequencies between .1 000 and 4000 Hz.are
evaiuated. The A-weighting, standardiz~.d in current sound level meter specifi~tions, has b¢en.
widely used for transportation and community noise description.A-l For many noises the ·.
A~ weighted .sound level. has been found to correlate as· well with human response as more
··complex ~asures·, su~ as the calculated perceived noise level or the loudness level derived ·.
from spectral analysis~A-2. However, psychoacoustic .research indicates that, at. least. for some
noise. signalS; a different frequency weighting which increases the sensitivity to the 1 000-4000.
Hz region is ~ore·reliable.~-3 yarious forins of this alternative weighting function have been
proposed; they will. be referred to here as the type "D-weightings". None of these alternative
Weightings has progressed in acceptance to the point where a standard has b~en approved for
. commercially. available instrumentation. • .....
. . . . . .. . : ···.· .· ·. ( . .. .
It is concluded that a frequency-weighted sound pressl:tte level is the most reasonable
~;hoice for describing tb.e magnitude of environmental noise. In order to use available stand-
ardized inStrwllentatiOn for drre.ct measurement, the A frequency weighting is the. only suit-
able. choice at this time.* The indication that a type· D-weighting might ultimately be more
suitable than the A-weighting for evaluating the. integrated effects of noise on people suggests
that at such:time as.a·.type D-weigbting become~ standaroized and available in commercial
instrument~tion~ its value as the weighting for environmental noise shOuld be considered to
determine if a chartge from the A~weighting is warranted. . ...
Tilne Cfuii-aeterlstics of Noise· ... :;_ ..... , .. .. ·: ,r ,•::: . . ·, .. :~ . . ..
, .... ·.·· · ... -: .• · ..... .:· ··.•· ..
.·:··.,·--: .
. '·· > _:The dominant :Characteristic ~fenvironmentalnoise·is·thatit is not steady~atany par,. .. ··· ·
ticula:r locatl.ori the noise usually ·fluci1l~tes considerably' from quiet at one instant. to lortd .... . . . . . ' .
*All sound·le\'elsin-this. report are A-weighted sound pressure levels in decibels with refer-
. ence to, 20 micro pasCals. · ·· · · · · ·
A-3
:·. · .. '.
.. ·.· ,.;_.: ... ~
·.;·.-...
·.< ..
the next. Thus, one cannot simply say -that the noise level at a given location or that experi-.
enced by a person at that location is, ''so many decibels" unless a suitable method isused to . . . .
average the time-varying levels. To. describe· the noise• completely requfresjf.statjsjical approach .•..
Consequently, one should consider the·noiSe e~posure ·which iS rec~ived: by·~cin.diviiiual. . .
moving through different noisy spaces: ThiS expdsure'istelated·to the·w6Q;u;,~:-varymg
pattern ofsound levels. Such a noise eXposure can be described by tl!,e ~Ulative distribution
of sound leyels, showing exactly what percent of the '\\fhole observation period eacJiJeyel was
. exceeded. . . . .. . .. ·· ·: . . . . . . . .
. • ! : _··:~ ': ".-: .-. . ~.;. . ., . . . .-.
A complete description 'of the nois¢, exposiu'e. wouid distinguisk behveei{ci.·ilytime, ey¢n"'· ': ·
. ing and nighttime, and between weekday and weekend noise leyel distributions. it would al~o-..
give distributions to show the difference between winter and summer; fair. weather and foul.
'.. The practical difficulty with the statistical metliodology is thatit yieldsa·large ntim.Oer
of statistical parameters for each measuriilg location; and ·even if these were averaged over
more or less homogeneous neighborhoods~ it stili would reqW,re alarge·set-ofri-umbers to
. characterize the noise exposure in that neighbo.rhoo<f._. ~tis liter<tllYirnpossible for a.ri¥. such
array of numbers to be effectively used-either in an enforcement_co~t~?Ct '()l'··'to' map. exiSting
tioiseexposure·basefutes~ ·, · · · ·: · ···· , .. · ·· .. · ····. :·<.······ :·.-·;··:··:·· · · ·· . ·.
.. . .. ·.' .·.·.;.· ·.·· .. · .... : .
it is essential, therefore, to look further fo~ .. a, suitable single-nutnbei.I}leas~e of noise ..
exposure~ Note that the ultimate goal is to characterize with reasonable accilracy the noise
exposure of whole neighborhoods (within which there Iliay actually exist a fairly wide range
of noise levels), so asto·prevent extremes ofnoiseexpoSufe_at any giventime,'ancf~o detect_ .....
·. unfavorable trends in the future· noise clirnate .. For these purposes~ :pinpoki ~cc~~cyand • ·.
masses of data for each location are not. reqUired, and may even be aJtindrance, Since one .
. . . -. ··.· . . . .
· · could fail to see the forest for the trees. . . . ....
. A number ofmethodologies for combining the noise .from both.individ·ual-events and .. -.. _ .. ,. ,.
.. · .... quasi-steady state sources into-measures of cumulative-noise exposure'have . .beeiideVe'loped:-~:;
in this country and in other developed· nations, ~.g;;, Noise Exposure Forecast; Composite ·
Noise Rating, Community Noise Eq-uivalent Level, Noise and Number· Index; and Noise
Pollution LeveL Many of these methodologies, while differing in technical·detaii{I;rimarily
in the unit of measure for individual noise events), are conceptually similar and correlate
fairly well with each other. Further, using' any one of these methodologies, the relationships·
between cumulative noise exposure and community annoyanceA-4,A·S also correlate fairly ·
well. It is therefore unnecessary to invent a new concept for the purpose of identifying
levels of environmental noise. Rather, it is possible to select a consistent measure that is-
based on existing scientific and practical experience and methodology a.11d which meets the
criteria presented in Section 2 of the body of this document. Accordingly, the Environ-
mental Protection Agency has selected the Equivalent Sound Level(Leq) for the purpose of
identifying levels of environmental noise.
A-4
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Equivalent Sound Level is formulated in terms of the equivalent steady noise level
which in a stated period of time would contain the same noise energy as the time-varying
noise during the same time period.
The mathematical defmition ·of Leq for an interval defmed as occupying the· period
between two points in time t1 and t2 is:
(Eq. A·2)
''· where p(t) is the fune vaiying sound pressure and p 0 is a reference pressure taken as 20
· . micropascals' . · · ·
. . ·. .
· The concept ofEquivalentSound-Level was developed in both the United States and
Ge~y ov~r· a penod. ofyears~ Equivalent level waS. used in the 1957 original Air Force
. Planiling·Guide for noise from.aircraffoperations,A-6·as well as in. the 1955· reportA .. 7 on<.
. criteria for short~ time' e,xposure of personnel to high intensity jet aircraft noise, which was· .
' -the forerunner ()'f thel956Air:Force R:egulationA-8 on ••Hazardous Noise Exposure".-A· .. ·
more recent _application is the development of CNEL (Community Noise Equivalent Level)
measure for describing the noise environment of airports. rhis measure, contained in the
· NbiSe Standards, Title 4, Subchapter 6, of the California Adm.iil.istrative Code (1970) is based
. upon a summation of Leqov~ a 24-hour period with weight.i,ngs for exposure during evening
and rtight periods. . · .. _ . . . _ ..
···-.··· ·-··--... ···-
The Equivalent Noise Level was introduced in 1965 in Germany as a rating specifically
to evaluate the:impact. of aircraft noise upon the neighbors of :tirports. A-9 It was almost
imm~diat~iy 'recogniZed ~ Austrfu aS' ·appropriate for evaluating the impact of street traffic
noise in dwellinggA~lO'-imd in schoolrooms;A-11 It hllS been embodied in the National Test
... Standards of bothEas~ Germany~~l2 and West GerinanyA-13 for rating the subjective ..
effects of fluctuating noises of all kinds, such as from street a~d road-traffic, rail traffic, .
-canal and river·ship-traffic, aircraft; industrial operations (including the noise from individual
machines), sp~rts .stadiu~s, playgrounds., etc. It is 'the· rating used in both the. East GermanA-I 4
and West GerrnanA-15, Standard gtiidelliles: for. city plaliriing; It"was the ratilig that proved to ·. · ·
correlate best with. subjective .respOns-e in the large Swedish ti'affic noise survey of 1966-67. . . ... . . . . ; .,... ·· ... · ·. . . '
.. -It has come uHo' such' general u5e iii Sweden' f<>r r.ating n-oise j!Xposure that commercial .
.. .. iflstrumentation iS' .ctiiiently av~ii~~l~-for inei:sUring L~q directly; the lightWeight urut is
small enough to-be-held i:n one--hand and can be operated either from batteries or an ele-c-
·trical outiet:A~l Q .
. ·.·. . . .... ·:··~
. ; ~ :-. ·., ..
·.·, .•
----------:---~----
........ : .... ·., ... .. ·.·:·;· ... _ ...... :
.·.:>·· .• • .. .. . · · .. •·.··· --·-:----~-
. ·:·· ·.:
. . . . . . .. . . :. .
· The concept of representing a fluctuating.noise leyel.U;l terms·of~--~tea.dyn.oise having
the same energy content is widespread in ·recent rese;n:,ch~ ;!8 shown .in the:<EPA-report on
Public Health and-Welfare Criteria _fo(Noise ( 197.3). •. There is-eVidertce.:that·it accimltely
desCijbes the onset and progr.ess. qf .p.e,rmanent no,ise-in.duced hearing:Ioss·,Ad-7 arui substantial
evidence to show.that it app~estoa~o~ce in vari.ous· ~c~tan~~~~l~. ~!.~.e.-conc~ptis.
borne out :by· Pearsons' expenmentsA.-:.19, on the· trade.offoflevel at1d ·i:futatton of a, notsy .· .
. . . event and· by. .. numerous investigations .. ofthe ~ade-off between number•'of eVe-nts and noise .
• · · ·1eve.l in air.craft flyovers.A"'20.. Indeed~ th~ Composite Noise RatingA-2Lis•a·forinulation•of ·
· .· Leq• modified by corre9tions.forday vs. Digbt op~ra·tiotis. theconcel'iis ~bod~ed in · .. ··
···several recommendations o.fthe International 'Standards Organization,. for assessi:flg the noise
· from aircraft;A.;22 industrial'noise a5it affects.re~denees,A;.2J. and hearlng ~on~~rvation in· ····
··· · ·· ·.· ·· · · factories~A-24 ... · .. >... ·· · '' •· ·
.·: ·::·· ..
. -.....
"!·'· .. :<·
····.··.;_. ...
COMPUTA TlOI'i' :OF·EQUIV ALENT SOuND LEVEL
·-.:-:·. .: ;:• .... -:~ ...... . ·:.-.·:---··
In lllaliy ap.plications~·it' i&·usef.uf to ):l~ve 1u.ta;lytic-expressions f o,r;ty;e ~quiv.~ent souitd
. level Leq in terms of simple parameters:Of.fh~·tiJiie~ar)dngnoise signalso that.~?e mtegral .
does not have· to pe. compute.(i;)t .:iS Often: suff~tly. accUI:ate:to approximate·a~-complicated
time•varying i10ise ievel with Simpie tilDe patterns. For example, industrial noise can often
be considered in· terms ofa ·specified noise levelthat is either on or Off as a function of ti.me.
Similarly, individual aircraft o:i: motor-vehicle noise events can· be considered to. exhibit tri•
angular time patterns that occur intermittently during. a period· of observation._(Assuming
an aircraft flyover time pattern to be triangUlar in shape instead of'shaped Ii.ke i ··•normal·:
distribution function" introduces an error of, at worst, 0$ dB):. Other noise l:ijstorles can .
often be approximated with trapezoidal time pattern shapes•
·,
The following se·ctions provide explicit analytic exptessions for-estimating the eq uiva-·
Ientsound level in terms of such time patterns', and graphic design chartS are preserited,f&r ·
.. ,~asy appfi.ca:~on to: ,practicil prob-lems; Most of the desf~· ch~ts ~~-expressed.'fu term:S:af--:".
· .,., · · the amount (.tili) that the level (L) of the new noise source exceeds an existing background
noise level, Lb. ( .c:lL = L-.Lb)• This: background noiSe: may. be consid.ere.d. as the equivalent
. sound level that existed before the inttoductionofthe new noise, provided that its fluctua-
tion is small relative to the maximum value ofthe new noiSe level.
A-6
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Constant Level Noise· Steady or Intermittent
The Leq for a continuous noise having a constant value of Lmax is
Leq = Lmax> which is derived from
1 Leq = 10 log T dt = Lmax (dB) (Eq. A-3)
When Lmax is intermittently on during the time period T for a fraction x. of the total time, ,
with a background noise level Lb present for the time fraction (1-x), Leq is given by:
· L.q = Lb + 10 log [o-x)+ x (10 ~~)] (dB) (Eq. A-4)
where ilL = Lmax., Lb. This pattern is illlistrated.and the expression is plotted in Figure
A-1 for various values of L and .x. For values of Lma:x that are 10 dB. or more· higher than .
Lb, Leq is approximated quite accurately by;;.·
Leq = Lmax + 10 log x (dB) (Eq. A-5)
Except in extreme. cas~s as noted on the graph~ .J\n h_ourly equivalent sound .level (Lh)" can be
computed from the last equation With ~the;iiitegration· "time. (T}equal to· 3600 sec·onds· ·
(1 hour). An'.example ofthe rela.tionship between Lh and· L~~ as a function-of pulse·
duration T forLmax • Lb' greater. than lO.·is:given in Figure· A-2. These results may be des-
cribed by: · · ·· · • · · ··
(dB) (Eq.A-6)
.. •.: ,••
.. ···.
. . . ·<;
· Triangular Time Patterns
The eqUivalent sound: level for a single.triarigulax time pattern having a .maximum val~
· of Lmax and ~ing from a background level of Lb is given: by: .. ·. : ·
[
10
23t!.L .
.. t!.L 1
ooio . l)J .
A-7
(dB) (Eq.A~7}
I·, ; : ~ .·.:· ,' ' .
.•'• .• w',.•
···.·,
., '•• ..
. ..
where agafu AL = Lmax -Lb. When . .O:L is greater·tlum lO dB, the following approximation
for Leq is quite a~curate: · .. : · ... ·: .. ·· · ..
. . .
· · 2.3AL .: L · = L . -lO.-log. ~1 .0 ... ·.·· ...... ·.· .. · .. . ..· eq. max . . . (dB):· · · (Eq .. A-8) :•, ... ·.···· ...
.···.·."
Except in.extrezpe cases as n~~ed OJ1. ~he graph. Th~ y:il~~ ?f leq for a .~~ries ofn._identidil
t,riangular,t~e patterns havin~m~~~m·Ievels: o(~~i~given by:. .. , .. · · . :·
,.· .. · ... • •.. ·: ·.•. •," .• ::·:! .. ·
~L ... J
(IOTO .:t .. ~ ~)· ....
2.3. .. 10 (dB) (Eq.A-9)
. ··.·· ... ·. ·.:· .. ·
. Where the duration between d-in~..; io.CiB) pcimts~·is T seconds, the background level is Lb,
and the totaltime period iST; (See .. FigureA~3)i·Adesign chart for determining· Leq for differ~
ent values of ALas a function. of nT per hour is· provided. in.·Figure A-3; · .. .
·. ; .. : .. , . : ·; .~·.:: .::' ; .
~ .... ,. . '· .
*The duration far which the noise leycl iS 'wiilifu I:Q·dB· 6(1.~·~; ~so .callecf the "1 0 dB
down" duration. · · · · . : .. · .... , ·. ... · · · · ... .. '•:. ·
'3~· :... .. ..:..· ---+---1----,;..j-+-.:...+-.......;;:.,......:...""""".;.-==-.:.,--~~
I _r
Figure A-1. Leq for Intermittent Lmax Added to LbA-25
A-8.
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. ·· ... .'
ASSUMED
PULSE
n--LMAX
-H--DURATION
COHBINED
PULSE DURATION IN InTI·
SECONDS PER HOUR 10.0
/
1.0 0.1
.'10 80 90 100 110
PULSE MAXIMUM SOUND ~EVEL(LMAX)INdB
Figure A~2. ·Hourly Equivalent .Sotittd· Level as a·Ftirictiori ofPulse Duration and· Maximum
· · · Soun,d LeveHor One Pulse·pel"Hout or a SucceS'sion ofn Shorter Pulses Having
. aTotalof the Indicateg DurationDuring Qne Hour. (Backgro'UJld sound leveL ..
· 'lesst:lian.:~30dB)~.{Derived'from Equation A-5). · · · ·
;.:··.
. . . .
·Figure A~3~. Leqfor a Repeated Series ofn Triangular Signals Overlaid on a B:il~kground
Level of Lb dB and T =Duration at (Lmax-10) dB in Seconds.A~4J .
(See Equation. A-9) .. • _ . . , . . ,. · ·.·. ..: •. .·
..... . A-9
:.,
. ·.:: ....... :
, ....... ·.
An approximation to equation (A~}Jor cases whereL is greater than lO dB is giveri by:
· · · nT Leq =. Lmax +·I 0 log 23'F . (dil). (Eq.A-10)
This equatio11 yields fairly good'results•·exceptin·extreme'~s asean/bese~n.tn.thegmph ... · .... , ·,
. . • .. ;:· •· .. : ;:• ·.-.... ·: •·· ... ·.:. : .. •.,:' ... •. ·: ' .":-> •• _,>r·.: ·.: ·.•.. . . -·.:_, -":":-·~···.·· ·.:::-::·.:···:···.-.·-:':: .... ·.. . ; . .-.. .
Trapezoidal Tnne Patterns
.. ·,······. ·.. .:_,._. ~ ._ .. · .... : . ,. . . . ... ~ ......
·.··' ··.·
.. . 'the.~Uivalent sound level, .Leq• fOr ·~:trapez~id31.time·p~ttem fui~;.Il1a~~~m: lev~ ....
· ofLmax• .background level Lb, duration between (Lmax -~·10: dB). poilt~:.()f T and d'uration, ·
at Lmax of ; is given by ·_ · · . ;.. .. . . . . . . . . . · ·. :,.,: ... ,;.·:: ';,·:·.:::: · ····.:·: .. .
... _..... .·.··· ... ,,, ...
Leq = 10 log (c~.~ ~llL :+· ~ )···.[~o~~ ('T -S l)
.. · 10•.... . .. . 2 . . .. 2.3 .
. · . . ........ ·-:: . . . '
(Jt_J.··
., ',· . r,:··
., .. · . +10 L~ 0)]: ' ,:· '
· The approxhnation to. Leq when ·lll,.· is great:er·thafi·tO'pll',for s · sm~l¢ompared to
is:
L · :. L ~ 2.3 LlL · + .· . .1 0 Jog s eq max· 10
:,::;;..._._;. :(d.Bi,., , ....... (Eq. A-12}
:.-.. · · ...... · ··· ...
., :,:-Tbis equation yields adeq~te .resul~s ~x:Cept·iii•ex:treme:eases as· noted' on the graph.
. Noting the simihirity between _equations (A·S)(A-&),..and{A-12); one· canapproxima~e Leq ..
for a series of trapezoidal pulses by ~uitably combinil}g design data fi.OIT1 figure A-land '.:: ..
·. A~3. That iS, theap.proximate Leq fo~ a series of i1 trapezQidal'Pul:Sesis,p.btainect:t>¥the Leq·:: ·::'···
value for triangular pulses plus an additional temi eqWil to 10 log n; e.g., · ·· ' · · ... ·· · · · · ·
.... _, .....
. -· .;., ·.'
.... , .... ·. .T.!T .
. Leq = _Lmax + 10 log 2.3T + ·lOlog n; (dB) . (Eq. A-13)
Time Patterns of N oiseJiaving a Normal Statistical Distribution
·· Many cases of noise exposures in communities have a noise level distribution that may
be closely approximated by a normal statistical distribution. The equivalent sound level for
th distribution can be described simply in terms of its mean value, which for a nonna1
A-10
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distribution is L5o, and the standard deviation (s) of the noise level distribution:
,.,
Leq = L5o + 0.115 s"' (dB) (Eq. A-14)
A design chart showing the difference between Leq and L50 as a function of the standard
deviation is provided in Figure A-4. ·
It is often of interest to know which percentile level of a normal distribution is equal in
magnitude to the Leq value for the distribution. A chart providing this relationship as a func-
tion of the standard deviation of the distribution is provided in Figure A -5.
Various noise criteria in use for highway noise are expressed in terms of the L 10 value ..
·.·_ For a normal distribution, the L 10 value is specified in terms of the median and standard · · ·
deviation by the expression L 10 = 1 50 + 1.28 s. The difference between Lto and Leq is given
··· by 1 10 -Leq = 1.28's--0.115 s.2 This expression is plotted as a function of sin Figure
A-6. .... ::·.·:
It sh~uld be noted that traffic noise d'Oe~ not always yield a normal distribution of noise .
levels, so caution should be used in determining exact differences between Leq and L10.
RELATIONSffiPS BETWEEN DAYTIME AND NIGHTTIME EQUIVALENT SOUND
LEVELS
The.day-ni~t sound level (Ldn) was def'med as the equivalent A.;weighted sound level·
during a 24-houi time period with-a 10 decibel weighting applied to the equivalent sound
level during the nighttime hours o£' 10 p.m. to 7 a.m. This-may be expressed by. the-equation:
·.
[[ lS(lO~/tO) + 9(!0 L :~O l]] (Eq. A-15)
. ~ · ...
··,· ..
. Cdin
·.·.·· . ... ··
. ·-···where
..... :·. •· ..
.. • .·
Ld =:=: ~J:..eq:~?.! ~~e ~aytime {07QO-:poo hours) · -·
·:.': •· . . . . ·: ·.. .. ... .
and ,• .·;· ...
Ln = Leq for the nighttime (2200-0700 hours)..
A-ll
',;_
.·:.:.;-.:
te r---------~------~~--------~--------~-------~--------~
16 ~----~-+----~~~-----~--!--------~----
.. ~-
•. . . -·~~ •. -: ·,. ··> •.. '
' .. ::. :.·.·
: • ... ;'·~·-~ .··· ....
· ... :.-: ·":•'''
· ... ····
. 14 ...,..__,... ___ -+---~-~
i:D
"'0
·= .·
0 •n
...J
I cr u
...J•
l2 1-"---~-:--..,.;.;...-l-----+--...;.-,_..;..., __ ,,4-_;.._-~
.. . ··
10
8
. : . . .
0 2
~. ·,;, .. ·
. • · . · .. ~-......... ~ .. ..: · .. · :: .. .
4 6 8
s ·.;. Stondorrf Devicit,ion in dB
10 12
Figure A-4, Difference Between Leq and Lso for a Normal Distribution Having Stand.ard
Deviation of s.A-25 (See Equation A-14).
A-12
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' Leq= L50 +0.115s·
I
10 .........-·
v v
/
/
v
/
v
I .. .·: . ..
20
30
40 v .. .. 500 2 4 10 8 12 14
· s in dB
FigJ.lte A-5; ,percentile Ofl:l Normal Distribution thatis Equal to Leq A-25 ·(See Equation
A-14 and Probability Function).
.4 .-----,~---,.,....,.....--..---....---..-1. -. --~~.--2 .....
. . . ___:. · L10 -Leq= 1.28s-0.115 s
//···.-~ 3~----~~~~--4~-~---+--~----~
/ \·· 2~--~~--~-----+-----+--~-+----~----~
4, / .. \ l'V -\
' ... ··· . .. \
. ~i l-.,....,....---~-----'----~-,----+--..;.._-+----4+-----~
2 4 6 8 10 12 14
s -Stan~r::! ueviati~n in .. dB
F~ A-6. ·.:Dif:ference.Between L10 and Leq for a.Noonal DistributionA-25 ..
.. ·· :·•. ··.···· ..
A-13
.·.:-·, ·:.
.····
: . . . . ~.
Figure A-7. Comparison of: the Differen<# Between pay,an£Night Val~es~f-theEquivalent
. Sound Level With the Day•Night Average·Sound·Level, LdnA-:> ·
:·.:_
The effect of the weighting may perhaps b~ more clearly visualized ifit is thought of as
a method that makes. all levels measured. at night'IO dB higher than they-.acttiallyare,<Thus,
as an· example, if the· noise level is a·. constant 10 dB. an· day inci ·a. constant '60 dB an: night, ·
l,dn:\VO.Uld_be 70 dB. . .. .. . ... ·. ... ·-·
Methods for accounting for the diffeten~s in:·interferen~ .or annoy~~ between day-
timejnighttime exposures have been employed in ·a· nwnbef Of diffetenffioiSe ·aSSessment
methods around the world~ A-5 .· The weightirtg5 applied'to:the·nohdaytime· periods· differ
slightly among the different countries but most of them weight night activities on the order·
. of lO dB';A~24 the evening weighting if used is 5 dB. The ch~ice of lO dB' for the nighttime
\Veighting made in. Section 2 was predicated on its extensive .prior usage, together with an
examination of the diurnal variation in environmental noise. This variation is best illustrated
by comparing the difference between Ld and Ln as a function of Ldn over the range of
environmental noise situations.
Data from 63 sets of measurements were available in sufficient detail that such a
comparison could be made. These data are plotted in Figure A-7. Th~ data span noise
environments ranging from the quiet of a wilderness area to the noisiest of airport and
highway environments. It can be seen that, at the lowest levels (Lctn around 40-55 dB),
A-14
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__--·.
Ld is the controlling element in determining Ldn• because the nighttime noise level is so much
lower than that in the daytime. At higher Ldn levels (65-90 dB), the values of Ln are not much
lower than those for Ld; thus, because of the 10 dB nighttime weighting, Ln will control the
value of Ldn.
The choice of the 10 dB nighttime weighting in the computation of Lciri has the follow-
ing effect: In low noise level environments below Ldn of approximately 55 dB, the natural
drop in Ln values is approximately-to dB, so that Ld and Ln contribute about equally to
Ldn. However, in high noise environments, the night noise levels drop relatively little from
their daytime values. In these environments, the nighttime weighting applies pressure towards
a round-the-clock reduction in noise levels if the noise criteria are to be met.
The effect of a nighttime weighting can also be studied indirectly by examining the
· eoi:relation between noise measure and obs~erved community response in the 55· community... .
i:eaction.cases.presente.d in the EPAreportto Congress of 197l.A-l The data have a standard
deviation of 3".3 dB when a 10 dB nighttime penalty is applied, but the correlation worsens
.. jstd. dev. = 4.~ dB) wi:ten no nighttime penalty is applied. However, little difference was.
... · observed among values of the weigliHng ranging between 8 and: 12 dB. Consequently, the
...... community reaction data support a weighting of the order of 10 dB.but they cannot be, ... ·
..··.·.··
· utilized for determiniiig a finer gradation. Neither do the data support "three,period~' in
preference to "two-period,. days in assigning nondaytime noise penalties.
COMPARISON OF DAY-NIGHT SOUND LEVEL WITH OTHER MEASURES OF
NOISE USED BYFEL)ERAL AGENCIES
The following subsections compare the day-night sound level with three measures
utilized for airport noise, CNR, NEF, and CNEL, the HUD Guideline Interim Standards
and the Federal Highway Administration standards: . . .. . .·.. . ..
, .. :. . .· .. _ .. ,: .. ·
CompariSon of Ldn with Composite Noise Rating(CNR)~ Noise Exposure Fo.recast
(NEF), and Community Noise· EqUivalent Level (CNEL} · · · · · · · · ·· · · · · ·
CNR, NEF, and <:NEL are all currently uied expressionsfor weighted,.accumulate_d
noise exposure. Each is intended to sum a.series of noise .. while weighting the sound pressure·
level for frequency and then adding··appropriate nighttime weightings. The oldei'ratings,
. CNR and NEF, are expressed in terms of maximum PerceiVed Noise Level and Effective
Perceived Noise Level, respectively; each considers a day~night period iderttic3.1 to Lciri· .
----·-----·-------_, ,.-. -:........-. ___ _
-.= .. ·•·· . : .• ·/.'.
·.···:·
The measure CNELitselfis essentially-the same as·Ld:n·,except for the methodof
treating nighttime noises. In CNEL, the 24-hourperiodis:brokenin:to·thi'eeperiods: day
(0700-1900), evening· ( I-900-2200}, arid riight (22()0-0700). Weightings -ofS d~ are applled
to the e-Vening period and ·.1 o dB· to the· night ·Period. Fot:m<>St' tirile distributions. of aircraft.
noise around airports~ the numeri-cal difference between··a:-two;;.~ffi;d ~ricfibii~~P6iiJd· day'' ·'
are not ~gnificant; being of tll~ ·order 'or'severaltenths -of~ d~~i~lat most; ·. · · . ·
. . . ·. •• • .. . . . _: ..... ·. ·: · •.. _-:.·: '·· .... _·:-· .• ••· ... ·:,~-~ ·, !'· .... ~;:~~::-:
One additional difference betweert these founkw.a.r nieasures-is th~method .of apply-
. ing the nighttime we.ighting and th~ ~tude of the \Y.eiglr(ing,. The original: CNR cori\:ept,
carried forward in the NEF; weigbted. ~e.,~ghttime e;x,posure .by.J 0 d:ij_; Because of the dif-
. ference in to·tal duration of the day and night periods, 15 and 9 hoursrespe9tively, a specific
noise level at night receives a weighting of I 0 + I 0 log (I~), or approximately 12 dB in a
·reckoning· of total exposure. Givet:t the clloice· of w.ting e.i~er exposure or level; itis
simpler to weight level directly; particul~ly whtm·aet~ no~· monitoring i5.:·ev:ent~~lly
consid~red. · . · . . . . · -. ·
-:::·;.· .. :. . : .. :. ~ ... ". .. . .
The following paragraphs describe the method:-utilized to· calculate CNR; NEF, and
CNEL, as applied. principally to aU-craft sounds, together with the_ analogo-us, method· for
caicuiatingL(iii: -··.·· ·· : .... , ·. ___ ,;. ... ·-,. ' , .:·:.: -,---.--·: .·">· , •... , .
Composite Noise Rating Method (CNR)
The original method for evaluating land use around civil airports is .the composite
· noise rating (CNR}. It iS still. in wide use by the Federal Aviation Administration andihe
Department of Defense for evaluating land use around airfields, (Ci:vil:Engiru~erln_g_;Planning
and Programming, "Land Use Plalining with Respect to Aircraft Noise," AFM 86~5, TM
5-365, NAVDOCKS P-98, October 1, 1964)~ Tius'no~e expos~ scale may .be expressed
as follows: ·.:·•:-•·-·· ·· ·
. . ' ~ ' ·:· .. ; : :. ~ ··: ...... ~·:..,
The single event noise level is expr.e~ed (with()ut.a: duration or toJJ,~: corre.ction)
· as.sfmply the. maximum perceived noiS~ level (PNLthax) iii PNdB: . .· ·· · ·. · · · "· · .· .
The noise exposure in a community is specified in tetms of the. composite noise
rating (CNR): which can be expressed approximately as follows:
CNR = PNLmax + 10 log Nf-12 (Eq. A-16)
where
PNL
._·, ... ,
= approximate •uergy mean maximum perceived noise level (PNL) a: 1 giveil
point
A-16
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Nr = (Nd + 16.7 Nn), where Nd and Nf the numbers of daytime and nig.ilttime events,
respectively. · ·
The constant ( -12) is an arbitrary constant, and the factor 16.7 is used to weight
the nighttime exposure in the 9-hour night period on a 10 to l basis with the daytime expo-
sure in the 15-hour daytime period.
Noise Exposure Forecast (NEF)
. .
This method, currently in wide use, for making noise exposure forecasts utilizes a· ..
perceived noise level scale with additional corrections for the presence of pure tones. Two ·
time periods are used to weight the number of flights (Galloway, W.J. and Bishop, D.E .. ,
'"·' · · "Noise Exposure Forecasts: Evolution, Evaluation, Extensions and Land Use Intefl)reta-·' ·
tions," F .A.A-N0-70-9, August 1970) .
.. .. The single event noise level is defuied in terms.ofeffective perceived noise level
. (EPNL):which can~.be,specified appr~ximately by: . · ... .'... ·· . . ·.
· EPNL '·· =. PNLmax + l~g ~t]g • + F, (EPNdB). (Eq.A~l7)
.. . . .
·where· ·. ;._ ···· .. ·
PNLmax =.maximum perceive<:~ noise level dUJ.ingflyover,in.PN:dB,
= "10 dB down" duration'·~f the perc~ivednois~ level time history, :·m ·s"econds, .. · · · · · · · ·
and.
. .. · .
... ·
.. -... · .
. -·,
. . .. . Community rioise exposure is then specified by the N~ise Expostire Fore cast (NEF). For a
given runway·and: one or·two dominant aircraft types, the total NEF for both daytime and
.. ni'ghttime operations can be expressed approximately as:·
. . .. ' . '
NEF · = EPNL+ 10 log Nr-88.0 (gq. A-18)
where
EPNL = energy mean value of EPNL for.each single event at the point in question
= same a~ defmed for CNR..
A-17
......
·.-....
-· •. '"1·-_ ... :
··•· ...
Community Noise Equivalent Level· (CNEL)
. The following simplified expressions are derived from the exact definitions in the
report, "Supporting Information for the Adopted Noise Regulations for California Airports." , .
They can be. used to estimate.valu~s ofCNEL whe.re.;l:>ne type-of aircraft and 6ne.-fliglifpath · '·
dominate the noise ex_posure lc;)v~l. · ·y . . .. _, . ·
-,~ ...
··.·
Single event noise· is specifie<Lby the single·event.noise exposure le:vel {SENEL).;j~ .
·. · dB and can·be·closelyapprcndm.ated.by.~, · ,. . ·. · .. :· · · · ...... ·· :·.···~ ·· .·.··. .. . ..
·:···.-·.-.· .-._ .. ;·
.SENEL = NL .. · . + 10log1·· 0· 1'/2' · max · ..
··.;-;_···. . .: . : . :. ·. . ~ ~ ....
··.··· .. ···-.. ·.:-·· . -· .... ·:_. . .. ~ .·.:-·:·
.,. where . ..... ·:': ... · ........... : ·: . . . ·· ...
= maximum noise level aS observed on the A scale. of a standard s.ound level · . . . .·-·-.-... . . . . --·. -· ... ·:· .
meter·
·.·.·.::.'·
·and
. T · .· = duration measured betWeen the points of (~max -10) fu seconds:· The
effective duration is equal to the "energy,. of-the -integrated noise lev:el (NL}, divided by
tM maximum noise level, NLma,X', whe~. ,b()th are. e~pre8sed in te~s of antilogs. ii is
approximately l/2 of the 10 dB down duration ... , · · · ·. .
. . '···
.. ·.·:·· .. : .. ·.
A measure of the average integrated noise level over one hour is also utilized in
the proposed standard. This is the hourly noise level (in dB), defined as:
-HNL . =• smmL + 10 logn•35.6 (dB) -. (Eq:A-20)
·.·
where
SENEL. = energy mean value of SENEL for each single event, : · ····
and
n = number of flights per hour
The total noise exposure for ·a day is specified by the community noise equivalent level
(CNEL) in dB, and may be expressed as:
CNEL = SENEL+ 101ogNc·49.4 (dB) (Eq. A-2!)
A-18
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where
or
and
Nd, if d = total number and average numb~r per hour, respectively, of flights during .
· the period 0700 to 1900
Ne, if e = total number and average number per hour, respectively, of flights during
the period 1900 to 2200
= total number and average number per hour, respectively, of' flights during . . . . . . .
the period 2200 to 0700
Day-Night Sound Level (Ldn>
. ;: ..
· The follow-ing simplifi'ed expri?SSions are u,seful for estimating the value· of Ldn.
.• fo:r.a,geries,of single.eventlloise~ which are of sufficient magrutude relative to the background
noise that they control Ldn:
Single eventnoise 1s specified by the sound exposure level (Lex) measured during
a single event. Itcan··be closely approXimated by: · ·
...... · ·.'·· ·.
(dB) (Eq. A-22)
where··: -~·· ... .-_.. ~--:. -:".·
Lmax:.. . . .. =::=. ml00n1um sound l~el.as observed on, the A scale of a standard sound level
· irieteron the:slow time·.characteristic .. ,
-·:·.--·::· ·:;' -.-. -.--.·.:···.· ... ·. ·.
T • · .. \,. dm~rlon meastired, betWeen the·p6iilts.of (L~ax ,. ·to) in ~econds.
·-. : .~ .: .. ;· .·: ~.. . : .· . -:-:. . -·. . . . . ' .. ~ . . . . . : . .
::.:The day-n~~t sound· level rna~· be. estirn~tedby: .· ·.··
. I ..
Ld · ' · . ·. ··~ Le·x· . + 1 O.log N. '-· 49.·. A.:. n. •. (dB)
. ·.where · ·:·:
L~x.
N
='~he energy meah ~alue ofthesin~deevent Lex values
·:, tNd + lONn}
A-19
.(Eq.A-23)
... :.··.·.·,: .. ·;
: ... , .. ··:.:-.. , .
or
= total number of events during·the period 0700 tp·2200;, .•.
and :·.·,·:· ·,,
= total number of events during. the perjci.d 22~0 to-070(), ....
. .·· ·:-·:··· .. : .. · .· ... ·: .. :· · .. ·•:.· ... ·, .. . ·., .. ·.
There ~;~o· fiXed tetatjc)liship.:~etvveen Ldn :Or,. 2NEL and CN~~~r N£F'because· of· .. ::·. .
the differences between the A-leveland,.PNLJreql!ency:weiihtin.gs and.t~aUowimqe.for~· ·· .. . ., ...
duration, as weii as the mino~ differenees -~ appro~ch to· day~ght conside~ti;;~~: Neverthe-... ·
less, one may translate from one measure to another by'the foiiowizlg appro·Ximaterelation~
shi··J>: ·, .. :.· .. .... <···..... .. .,,,; •.··.·.· .. ·· .. ·
': • · •• ;0. ~ ·.~· •• ". " .•• ·. • ...... ~
Ldn
:·· .: . = CNEL = NEF + 3S =c.NR ~ 35 . ~:-..... .-:·.·. · ..
-· ··:: .. .:.:
: {~q;:A..;24} . ·...... .·.: .. . :. ~· .
. For most circumstances involving aircraft flyover noise; these relationships are··valid \Vi thin
about a :1: 3 dB tolerance.
. ··.·· .. ·.::
CompariSon of Leq with HUD GUide~e Interim ~timdar~·(l3?0.2 Ch~.l) ··
·The interim HUD ·standards for outdoor noise. are specified for ali· noise SG,)Ur~es,: other
than aircraft; in terms of A-wejghted SOUnd level not to be ·exceeded 'mote than a certain
fraction of the day. Aircraft noise criteria are stated in terms of NEF or CNR. .
....
The HUD exposure. criteria for residences near airports are "no:mlallyaccepta~le~' if · ...
1\'EF 30 or·CNR 100 is not exceeded. A "discretionary acceptable'' eategory. permit~-
. exposures up to NEF 40 or CNR 11 S. ·
· ...... ·· ···.······· .
·. ·~· ..
· .....
· .. ··
· . For all o.ther noise sources, the HUD criteria specify a· series of ac~ptable;· cliscretioriaryi · ·
· · and unacceptable ·exposures. Since these specifications are simi~ to P.oin.ts .on a .cuin:ulati~e .
. . ,:. statistical description of noise levels, it is of interest to oot1lparetheHlJ.D:giteria ~th Leq
for different situations. For discussion purposes, consider the boundary betWeen the cate:-
···· · · .. · .· .. · gories "discretionary-normany acceptable" ~d "unacceptable·."
The first criterion defining this boundary allows A-weighted noise levels to exceed 65
dB up to 8 hours per 24 hours, while the second criterion states that noise levels exceeding
80 dB should not exceed 60 minutes per 24 hours. These two values may be used to specify
two limit points on a cumulative distribution function, L33.3 = 65 dB and L4.2 = 30 dB .
. The relationship between Leq and the HUD criteria may then be examined for different types
of distribution functions, restricting the shape of the distribution only so that it does not ·
exceed these two limit points.
[
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.
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. . -~-·. . '.·
First consider two cases of a normal distribution of noise levels, comparable to vehicle
traffic noise. For the fJISt case, assume a distribution with quite narrow variance so placed on
the graph that the 65 dB point is not exceeded (see Figure A-8). For this curve, to the nearest
decibel, Lso = 64 dB, and the corresponding standard deviation (arbitrarily chosen small) is
2.3 dB. The resulting Leq is equal to 64.6 dB.
Now consider a normal distribution with the widest permissible variance (the curve
marked Maximum Variance in FigureA-8); if the variance were any greater, the distribution
would violate HUD's requirement that the level not exceed 80 dB for more than 60 minutes
per 24 hours. This distribution, to the nearest decibel, has Lso = 60 dB, L 10 = 74 dB and a
standard deviation of approximately 11 dB. The resultant Leq = 74 dB, is almost 10 dB
higher than for the previous case. Both curves meet HUD's interim standards. ...../
Next, consider a series of intermittent higli level noises, superposed on a typical urban/··
· suburban background noise le:vel, such that 80 dB is not exceeded more than 60 minutes per .
24 hours, say 4%. Choosing a series of repeated triangular-shaped time signals of 90 dB maxi-
. mum sollll:d level will produce_ an Leq value:.of 72.4 dB without exceeding an L4 val1:1e of 80
. dB. :. . . . ·· .. · .. · ··· ·. . •· · · · · · .· :.
••• •. < ._ •• ·
· · .. Ho~ever;mie can allow the:maxim1J:I11level to increaseindefinitely provided L4 remains
at 80 dB or less. The linliting case is that of a square_.shaped time pattern, switched on and
off. In this irtstance_, if the total "on ... time" is 4% or less, the value of Leq is equal to· Lmax
-14 dB, illld both fmax and Leq can. increase without limit and still remain acceptable
within the HUD interim standards •. Maximum A-levels for an aircraft can be as high as 110
dB, which would perymt Leq val~~s of 96 t.o be obtain_e~ without exceeding the L 4 .1imit
of 80 dB.· ·• · · · ·· · · · · · ·
It .is dear that no uniq~e: relationship Can be ·specified between the HUD non,.airport
. stand~ds.and ~eq· Values qf L~q·rilngirtg ~.P to 9.5. dB can he found in compliance with the
. HUD outdoor n~e· standard deP.encting ·on the .time distribution. of noise levels considered,
Even if th~·.rugli~~::penaity:~e~·app~d.to Leq· t,~·Yield Ldn there would ~till be no unique ..
· · relation· with the HUDc·standanfs'.> ·· ·' · · ·
·-::.:····.:.•. . ... ·:::_·.·
Comparison Of~L~~With F'ed.eral Highway Administriltion Noise Standards, PPM 9().;2,
February·8;·1913· ···.: .. ·· .·· .. ; .. , ... ·.·:< .·: .. · -.· : .. · . . .· .. ,·.' ........ ·:· .: .. •,; ' .. :: ... _ :·: .. ·. . ' ' .. ·.• ···~ : ._.·:.· .. . ····. . • ..
. The_ ppmary: c;ziteria. of J:ll'M· 90~2 are that Lto for·iioi$e levels inside .people,-occupi~d
spaces shall not exceed 55-dB,.or for sensitive outdoor spaces .. _in which serenity. arid· quiet:·. ·
aie of extraordinary signiflcance-,?. 60 dB. . ·· .
. · .. •. ·.·.. ..; . ' ': .
A-21
.. •' ' .... -~ ..
-.: ...
· .. · ·.:·
. · .... ~-., :-.-.. ' ..
:.": ....... .
· . ... ··
,··,.
\ '··:: .
. ~. ~ ...
.· .. : .. ·
. ... ;:. :.·. '· ... '; -~ ·: ........ -:·';. ·.: .
,·,·. .., .· ........ ·:
.·:·':; ..
. : . . . ~ ... .::··
· .. ·::·
g g: 99.9J:-I-:-J-+-+++++-,.+-hH~444'-+·+~ . , ...
I&J 99.8H-i'-+-++++++-+-HH-i'-+4.'-~~.1 .-+--l ~
~ 0 a: 99;5J:-I-i-+-+++++-+ ... -.. ~HH-i-+-++++:4
8 99 .!~
.. ·4 ,;. 98' ··.· 0· .
1-:.: . ~· ,,. ~.;.
N ~~ N
;!; 90 '-MAXIMUM . . a: •
Cl _ S VARIANCE'· · '.. . ILl· .. ~ so >-'"'KIA' ' · 7 1-Nli" · ~ u._: · ~. · t::f· .. 70 ,['.< ... .. ~ _J.. +-+-H ;;'-
~ ~-~
I&J ·60H-i-+-++-P-.d-+--I-\-~+-'IH..-...J-+-+.+.·++4··:::) :::». · ....... ·
50 ., \ ~!E·
40 . ['>.. \ 10
30 "'' ,___ 8
' 20H-+++-+-H;..:.· +. +4'+·~~++--1-lf.-.;.!:4-l-...ff--,._.;;_ 6~ ... . \. r-..., ··:~~:l.:.: IOH-+-+-.. -+, -, + .. ..,... .. ,!.,., .. +-.. +-H~-+--P-t-'-;,-. .j.;.,-+o-...j..:...;+'---:io-1120 2
5H--+-H++-:t-,. ... ,+ ......... l-+:.-l,"-\..J-:..I..,...j..~l-~-1-.... ~ ... !.-. +. -l .. 160 • -~~, ...
2 ' . ~·":s
LO: HUO'INTERIM NOISE .... : \ .MINIMUM . IS
Q;S EXPOSURE STANOAROS ~ "vARIANCE,_;_~ . ,
0 .2·. ,,GIRCULAR·l390;2,CHANGE I •···
. . 911171 !
O.~ ·NA-'NORMALL'!'_ ACCEPTABLE ._,.:::f-HH-+++-+-1
N~-NORMALLY UNA£C~~AB~E .. · .. · .. ,,
o;Ol U UNACCEPTABlE 1 1 1 1
4() 50 .60 10 ao· 90
A;..LEVELidB)
< .. ·.· ·.
·:,:-.-·
Figure A-8. Permissible Normal Distributions of Leq Under HUD StandardsA~25
A-22
...... , ...
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L
v·
Highway noise often has a random distribution of noise level, the distribution function
being approximately normal in many instances. In this case, the relationship between Leq
and L 10 is given by the expression:
Leq = L 10 -1.28 s + 0.115 s2 (dB)· •(Eq. A.;.25)
where s is·the standard deviation of the noise level distribution. The difference between L 10
and Leq for normal distribution ofsound level is plotted in Figure A-6. It can be noted that
Leq = L 10 -2 dB within ±2 dB, for sranging from 0 to 11 dB. Highway noise rarely has a
standard deviation of 11 dB; 2 to 5 dB is more. typical.
Thus, setting t 10'at 60 dB·for highwa·y noiseimpacting a sensitive outdoor space, we.
·>find that an Leq valt~e of 60 -~ = 58 ±2 dB would meet the most sensitive FHWA cri~erion. · ···· ··· ··· · ., · · ...
--·:···
._.,_.
:-:·,
.. :--.-._ ·-:-. . ... _;··.
-·-·: -_ ... -~ :.-·--·-:.. .-.-, .. ·.;.
,· : ~-. · .. •.
·,···-=-·-·
. . . . .
.·.· ...
: -~ .. ;
...... ··::·: .---::·,··· :·
····; .. :,;·:·:··'·_ ... :·:-·-. .'··:
·_ ~ . . . :·::.
·-.· .. ,
·:·.·,_.-
-···-· .. -.... ,-;_
A-23
··;.:·· .. ........ :.::-· ·.:
·.' '·•
...... .REFERENCES. F,OR APPENDIXA .•
. ' -~.; .. : ··.• ~ ..
'"•,# ' .... • •
. '· :· .· ~. '
A-l. ...
... ·::·-
.. · "Reportto: the Pres,ident andcCongress on Noise';~' ~onmental.Prote~tion Agen~y ~
NRC 500.1, December 31., 1971. .. ··· . · ·.-: ·' ·· · .
.. • ·-'. ·.:· .'
···,·A-2.· ·Rishop, D:E., "Judgements of the' Relati~ andAbsblute Accept~bility of A~craft. ' ... ·
·.~ . ~;' ':. . . . . . Noise;.· J..Acoust. Soc; Am·· :40~103, Deceiltl:>er 1966. · · ·
.. · .. :-... ·.·.
A-3.
. . : . . . . . . . .
A-4.
Kryter, K.D .. , "The-Effects ofNoi~on M~n/'·Acad~Jnic'Press, ~ew York: 19c7o •.
;•.:: . .. . . .
"House Noise• ReductionMeasurements_forU8e· in·Srud!es of Aircraft Flyover
Noise,n Socie~y ofAutoinotive EngineerS, btc., AIR l08l,Octo'ber 1971 ..
. -.:·,
.A-5; ·· · · .. B~op,.~--~., and Hor~hjeff, R.b., ... Pr~duie$ror~~~lopirig.#o~ E~posure Fore-
cast Areas for Aircraft ·Flight Oper~tionsj ..... FANR~port DS-61;;10; August 1967 .
. .. _.·:· . . ·. ..... . . . .··' . . . . . .. , .
A-6. Stevens, K.N., ~dPietrasanta, A.C., and the Staff of Rolt Beranek and Newman,
Inc., "Procedures for Estimating Noise Exposure and Resulting Community Reac-
tions from Air Base Operations," W ADC Technical Note 57-lO, Wright"Patterson
,''A'-7.
. A-~L ·
A-9.
.·Air Force· Base, Ohio, Wright Air Development Center, 1'957. · · '· .· . -
' Eldred, K;M'.,<Gimilon; vi.J., and von Gierke,.H~E., ·~criteria for short .Time
· Exposure of Personnel to High Intensity Job Aircraft Noise," WADC Technical
Note 55-355, Wright-Patterson Air Force Base, Ohio, 195'5. · ·
:·.-.. :.-:·
Air Force Regulation 160;;3, "Hazardous Noise Exposure,'' USAF~ October29, · .
·1_956·.. ' ....... .
Burck; W., Grutzmacher, M., Meister~ F.J., Muller, E.A., and Matschat, K.,
"Fluglarm, Gutachten erstattet im Auftrag des Bundesministers fut Gesundheitswesen,"
(Aircraft Noise: Expert Recommendations Submitted under Commission from the
German Federal Ministry for Public Health), Gottingen, 1965.
Bruckmayer; F. and Lang, J ., "Storung der Bevolkerung durch Verkehrslarm"
·(Disturbance of the Population· by· Traffic Noise), Oesterreiche Ingenieur-Zd tschnft,
:;. 1967, H.8, 302-306; H.9, 338-344; and H.l 0, 37 6-385.
A-24
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A-12.
Bruckmayer, F., and Lang, J., "Storung durch Verkehrslarm in Unterrichtstraume"
(Disturbance Due to Traffic Noise in Schoolrooms), Oesterreichische lngenieur-
Zeitschrift, 11 (3): 73-77, 1968.
"Schallschutz: Begriffe" (Noise Control: Definitions), TGL 10 687, Blatt 1 (Dr.aft),
Deutsche Baumformation;East Berlin, November 1-970.
A-13. "Mittelung zeitlich schwankender Schallpegel (Aquivalenter Dauerschallpegal)".
(Evaluation of Fluctuating Sound Levels (The Equivalent Continuous Sound Level)), .. ·
DIN 54.641, (Draft), Deutsche Normen, Beutti-Ver.trieb GmbH;Berlin· 30; Aprill97'L
A~l4. ..Schallschutz.: Territoriale tind Stadtebauliche Planung" (Noise Control: Land Use
·and City Planning), TGLlO 687, Blatt.6, (D~aft), P~utsche Bauinformati~, East
Berlin, November 1970.
A.,J5. ..Schallschutz inStadte.bau" (Noise Contr.ol.in City Planning), DIN 18 005, (Draft),
· ·.Deutsche. Normen),·Beuth..,Vertrieb. GmbH~:Berlin 30,, August 1968. . .. . .·
. ; ' . ·: . -. . -. . .. .. . . . . . . . . . .. · . . . ·--. . -: . . . . .. ·_ ~ . . _, -.
A-16. ·.· · B~njegard,.Sven-Ola.f;·"Bullertfosimetern'~;(The Noise D.ose Meter}; Report Sl/69~
Statens institut fur byggnadsforskriing~Stockholm, .1969.
A.,l7. Robinson, D.W., and Cook, J.P., NPL Aero ReportNo. Ac 31, National Physical
Laboratory, Engbind, June 1968. . .
· · A-18. ·Meister, F'.1:, "Der :Efufi~'Ss cie~ Emwirkd~~er bei dei Beschallung des Ohres'' (The
1ttfluence of the Effecti~ Duration in Acoustic Excitation of the Ear), Larmbe-
kampfung 10 (3/4), June/August 1966.
A;19. Pearsons;K.S., "The Effects·ofDu!ation and Background Noise Level on Perceived
· ··Noisiness,'~ :FAA ADS-78; April.l966; ' ·. ,, · . ·
A-20.
, A-!1.
. ·.· ,-.
'~Procedure for Describing NoiSe .Aro~d an·Airport/' R-507, Intemati~nalStan,.
·'· dards Orgiirtization, Geneva. 1970. . .
. ·, ~ ··-' .. ·r:;
· A-22. · ·"Noise Assessment with Respect to Community Noise," R-1996, Intema~ional
Standardsqrganization,Genevll, 1970. . '
; ·.:: ·.
. .. ·:·:···: _:-.· _,_ _.-...
A-25·
····~ ...
. :-. ~ . . ··;; .. -.. ' .
-:·
. :'·_.-...
· .... ;; ~ .... ~. :.
· ...
;.· .... _.--.
A-23.
<·.:::::.
··'•;.
.. .... <
''Assessment of Noise-Exposure DuringWork for Hearing Conservation," R-1999,
hiternational S~andards .OrganiZi~~n, .. Geneva; .197-0~ .. , .. .. ········.. ... . ......... .
: ....
Galloway~ W.J ., .. Review of Land' Use Plaiuimg Pio~urei;; I~t~rll'n,r ecl.Ullcal
:R~port, .Aero8pace Me~cal R,:esear.ch Laborito,Y,;;\vPAFB, :obi'0:;:¥3,i~:i9:ti.
.-: .. . ........ :
••tmpact CharacterWitioii of Noise Including Implications ofldel1ti.fyfu,g·_and
Achiev.ing·Leveis of Cumulati¥e: Noise ExP:<>sure;·~_T; EiiVi!onrfi~iitar:Prot~Ction
. Agency,i.fTID73A,.l.973-... .... . · .~.·· . ·· .· ·· · c
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,;-•.-.:;·_::.· .. · · · · ·APPENDIX·B ·
LEVELS OF ENVIRONMENTAL NOISE rN THE u.s. AND TYPICAL
EXPOSURE PATTERNS OF INDIVIDUA~
·.,, ·.
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APPENDIXB
LEVELS OF ENVIRONMENTAL NOISE IN THE U.S. AND TYPICAL
EXPOSURE PATTERNS OF INDIVIDUALS
Levels of environmental noise for various defined areas are provided for both the outdoor
and indoor situation. Examples are· then used to illustrate how an individual's daily dose accumu-
lates from the exposure· to such noise levels.
LEVELS OF ENVIRONMENTAL NOISE
. . ~ .
Outdoor Sound Levels
The. rang~ ofday;.nightsouncllevels(Ldn) in the United States is very large,extending.
from the region· of 20~30 dB estimated for a quiet* wilderness area to the region of 80..90 dB
in the most noisy urban areas, and to still higher values within the property boundaries of
same govern~ental, industrial imd commercial areas which are not accessible to the general
public. The measured range ofvalues. of ~y-night sound levels outside dwelling units extends
from 44 dB: on a:farm. to 88.8 ·dB outside an .apartment located adjacent to a freeway. Some
examples of these data are swrimarized :in Figure .B .. L ·
The ·dominant sources for outdoor noise in ·urban residential areas are motor vehicles,
aircraft and voices."'This conclusion has·been found in several studies, including a recent
· ·sbrvey B-1 oft2oo people:.which is sum~arized in· Table B• L · · ··• · : · . :·. · · · ..•.. · . . . . .. : . . . ..
.•:. :·.
. . . The ~~Ulative numb~ ofpeopl~··~~tilnate(n~ reside tri: areas \vhe~ the day.:Oighf sOuru( .
level exceeds Various valuesjs.givenin Table B-2. In.the areas where the Ldn·exceeds 60 dB,
the prOpOrtion betWeen the nUm:bef·ofpeople r:esidfug in areas where the outdoor noise . . .
environment is dominated. by ilicraft .and those.residing in areas.where. motor vehiCles domi~··· · ·
nate is approXimately one to tolit~ ThiS' proportion.i.S almost identical to the proportion . . ·
.· found·in the survey; previously 'sUnUnarized in Table B.,.l. where· people were asked to judge .
the principle eontributing sol;II'ces. of neighborhood noise. The estimates in Table B-2 of the·
*Meas~ement appro,ilinat~ly 25'feet from a m~untain waterfall on a small.canyon stream
in Wyoming gave an: Ldn of approximately 85 dB.B-2 · · · · . · · , ·. ·
·· .. ··
B-1 ~d./
;. · ..... ·.
.· .. :·
. . .
-'QUALITATIVE
DESCRI PnONS
.·-
: ~-. .
,.
....
·.·_,.
Ldn
DAY~NlGHT
SOUND LEVEL
DECIBELS-
.... ·.
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:. . . . . . . . ... ~ ........ ·.···
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, .. :· :, ·~ .. • .-..
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:··f.' ·~.·~:·· ::: ~ :·.: .. : ..... · .·
.· ... .···.: . · ....
. . . ' .. . . ~ ';--:·:. . ···:: . . .. .....
:OUTDOOR L<)CATIONS .;;;g<)·.;:. .·
... · Los :ANGELEs,;;;;; 3rd··FLooR·APARtMENT NExT To·.
·.· ......... ,: . . ·FREEWAY· · ._.::
· i.os ANGEl.Es'-~3,4MILE f:RoM.roucH ·oowN AT ·:·.·.
,··.·.·.·· · .. ·· -, -· . . .. . :) MAJQ.R,A~Rf?~Hn·. :
·.· ... · .. ,,,
· ·. ··. t..os ANGELES-· oowN.towi'J . wt:TH: soME .cclN-·· ...
·.. ..·. : _,' .... STRUCTI'ON: ACTIVlTY .
.. .. · '··
HARL£.M~: .. 2n<I .. FLDOR APARTMEK-r-....
·.: ... _..; ....
. ;_. ~ .. :. ::.-.
Figure B-1. Examples of Outdoor Day-Njgl}t~ound Level in dB (re 20 microp;:tscals)
Measured at Various LocationsB
B-2
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Table B-1
PERCENT CONTRIBUTION OF EACH SOURCE IDENTIFIED BY
RESPONDENTS CLASSIFYING THEIR NEIGHBORHOOD AS NOISY
· . (72% OF 1200 RESPONDENTS)B-3
Source Percentage
Motor Vehicles 55
Aircraft 15
Voices 12
Radio and TV Sets 2
Home Maintenance Equipment 2
Construction 1
Industrial 1
... ~ .... ·. .. ·: ', . ..
··:·:· '
Other Noil;es : .. : 6
· Not Ascertairiecr 8
Table B-2
ES'l=IMATED CUMULATIVE NUMBER OF PEOPLE IN MILLIONS IN ..
THE UNITED STATES RESIDINGIN URBAN AREAS. WHICH ARE EXPOSED
TO VARIOUS LEVELS OF OUTDOOR DA Y/NIGHf A VERAGESOUND·
LEVEL, B-4,B-5
··, ....... ..
. Outdoor
Ldn· Exceeds
60··· ... ··•.·.
· .. 65·
··7o·.:.···_".', ...
1s·' ·.
. --so-·,·
. :UrbW. . · · .. . .. . FreewaY
Traffic· Traffic
.:·· 59.0
24.3·--
, ·· .. 6.9-: .. -
.. _,· .. }.3:.: ... ".: •.
'•.
0.1
. .3.1 :.·
25:
1.9 .
''·0.9 ....
B-3
. Aircraft·
Operations
16.0
7.5 ..
3.4
1.5
0;2
·• Totii.l ·
···:
78.1
..343.
12.2
3.7
. 0.6·
•. I ~.'
.··'.•
number of people living in areaswhich.are exposed to freeway and aircraft noise are taken
from the EPA airport/aircraft.noise report. B-4 They were based on calculated noise con-
tours and associated populations for a few selected situations which formed the basis for .
extrapolation to-national valu~~. The· estimates for .the number of people living' in areas in
which the noise environment is dominated by urban traffic were de~eloped from a sut:veyB,.S
conducted in Summer 1973 fqr EPA. The survey measured the outdoor24-hour·noise
environment at 100 sites located in 14 cities, including at least one city in each of the ten
EPA regions. These data, supplement~d With that fr.om previous measurements at 30addi-
tional sites, were correlated. with census tract populatiol1 density to ob~ a·~neral rela-.
· tionship between Ldn and population.dtmsity. Thisrelationshipwas then·utilized; together
with census data giving population in urban areas as a function of population density' to
· derive the national estimate given in Table B-2. ·
These data on urban nOise enable an estimate of the percentage urban population in
terms of both noise levels and the qualitative descriptions of uroan resid.ential areas which
were utilized in the Title IV EPA report to Congress in 1971. B-6 · .
These estimates, summarized in Table B-3, show that the majority of the 134 million
people residing in urban areas have outdoor Ld:n values ranging from 43 dB to 72 dB. with a
median value of 59 dB. The majority of the remainder of the population residing.in rural or
other non-urban areas is estimated to have outdoor Ldn values ranging between 35 and SO
dB.
. Indoor Sound Levels
· The majority· of th~ existing data regarding levels of environmental noise in residential
· . areas has been obtained:_ outdoors. Such data are useful in characterizing the neighborhood
noise environment evaluating the noise of identifiable-sources and relating the measured
values with those calculated for planning purposes. For these purposes, the outdoor noise
levels have proved more useful than indoor noise levels because the indoor noise levels con-
tain the additional variability of individual building sound level reduction. This variability
among dwelling-units results from type of construction, interior furnishings, orientation of
rooms relative ·to the noise, and the manner in which the dwelling unit is ventilated.
Data on the reduction of aircraft noise afforded by a range of residential structures
are available.B-7 These data indicate that houses can be approximately categorized into
"warm climate" and, "cold climate" types. Additionally, data are available for typical open-
window and closed-window conditions. These data indicate that the sound level reduction
provided by buildings within a given community has a wide range due t'J differem .. es i:1 the
use of materials, building techniques, and individual building plans. Nevertheless, for
B-4
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Table B-3
ESTIMATED PERCENTAGE OF URBAN POPULATION (134 MILLION)
RESIDING IN AREAS WITHVARIOUS DAY-NIGHT NOISE LEVELS TOGETHER
WITH CUSTOMARY QUALITATIVE DESCRIPTION OF THE AREAB-3,B-4
Estimated
Average Census
Typical Tract Population
Description Range Average Percentage Density, Number.
LdnindB of Urban LdnindB of Peo.ple Per ,.. . . . . .... . Population Square Mile
Quiet Suburban 48-52 50 12 ·630
Residential-,·.
Normal. Suburban · .. 53-57 55 21 2,000·
Residential ...
60 28 Urban Re~dential 58-62 6,3(_)0 · ... . ,, .. .·.··-... ·~ ... . . . '. ! . ~ ·-•. ·; ··,·. ·· .. ·· .. '.
. NoiSy Urban 63-67 65 19 20,000
·. · Residential ..
Very Noisy Urban
. . .. .. : ·• .. ····.;·. .··.·. ..
68:;72 ... , 70 7 63,000
Residential.
,_._
....
. . ' .
. planning purposes; the typical reduction fu sound level from outside to inside a house can
be summarized as follows in-Table B-4. The. approximate national average ''window open"
. condition ·corresponds to an opening of 2 square feet and a room absorption of 300 sa bins
(typicilaverage of bedrooms and living rooms). This . .window open condition has been .
.. assumed-throughout this report in estimating cOnservative values of .the-sound levels inside . ·•
·• · ' dwelling unit~ which results from qutdo()r noise.· · •· _. .. ·
:·.·. . -·. . . . . . .
..
The sound levels inside .dwelling. wtits result from. the.noise from.the,outside--environ .. • ·· ·.·.· ··
. ment plus the noise generated ~te~ally.The internally generat~d nois~ results from people
activity, appliances and heating.and ventilating equipment .. Twenty-four hour continuous
measurements ·were made in_l2-iiving ·rooms. (living, family or dining .room) in 12. houses · · ·
. ... . . during tile 100-site EPA surveyB-5-~f Ul"ban noise, .exCluding areas where_ the noise .. resulted·
-. . ._from freeways and aircraft. The_ :r~s1;1Its, .. summarized. ,below in Table B-5, sho:w that the inside·
· •; '. · day•nights'oundievel iii tlWSe·homes was .. the result ·Ofinternally generated,<noise~. in fact;. .
·. · ..... 'the interpal Ldn. aud Ld values. were':~lightly higher them tho~~ measiired· outdo'onl,: despite ·
· · the fact th.:rt,the average house .sound.levelreduction.appeared to exceed· 1:8. dB,_ The pattern
for the indoor'.soundlevels varies s1gnifii:antly among the homes. as portrayed by the data .
in Figure B-2~ The ·hourly equivhlerifsoi:in.d levels ha~e an. average minim fun of approximately
. . . .;:-,_ ~-.
: __ , ·.·· ..
Table B-4.
soUND LEVEL REDUCTIONDUE'fO HousE:s•I:r;rwARM AND coLD ...
CLIMATES, WITH Wl·i'IDOWS OPEN AND CLOSEoB4 • .. · '······ .
Warm· climate 12dB
Cold climate . . ·· ·r7d'B ... •> : '·.·-:·· -: .:·-:·
Approximate national average 15 dB
...... ,
·····,
·:Wiildows' --·····;--... ·:-.·cli!lsed~-.. : .. ··
··· .. 24dB '.
···--·:·>-·-:·:··-··:-· .
··:)?'dB
....... 2S ci:B :·
--~.;--
....
*(Attenuation ·of outdoornoise by e:x:terior shell of the'ho:t.~se}.
: =-~ •;.. . • .,
-__ ;.:
. . ..,
. :··-; ,. :'
Table B-5>
COMPARISON OF INTERNAL AND OUTDOOR SOUND LEVELS IN
LIVING AREAS AT.l2 HOMEsB-7
;·._, ... _; .
'"·"···
. · Daytime ·. • . ·.· Nighttmif · .· riay,;Night
Sound Level Sound··Level Sound Level
· (Ld) :ii1 dB ... CLn) ·in· d~ .1 . Lct~ in dB
Outdoors:
Average
· · ·· Standaxd-'Deviatioh
Indoors:
Average
Standard Deviation
Difference:
Outdoors Minus Indoors
B-6
..... . .... ,
·s1.1
3:1'
59.4
5.6
1.7
i
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49;8
4.6
46.9
8.7
2.9
··ss.s
3.6
60.4
5.9
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2 • • • I • • • • • • • • • • • • • • •· • • 0 I • • .. • N • • • • • • • • • • • I • lJJ • • • \ • . • • \ • a: • .. • I I • • • • • • • I • • • I . • • • • lXI i :-• . • i . • .... . • • • • . • .. . t .. . \. . . .. z i lttl I •· .. • ·• • • • • • I I . • ..: ! ' . •
...1 ' ' •
..,
• • .. •
6 9 .. 12 . . 15 18 21 24
. ·.-· .. ·
NOON MIDNITE
.· .. :.-;·_:;.-
·.· ·· ·· · ·· Figure·B:.2~ . Noise Inside Living Areas· of 12 Homes-Values of Hourly Equivalent
. S'ound. Level as a Function of Hour of DayB-5· .
. .
36,dB during the· hours between.!· a.m. and 6 a;m. This minimum level is probably governed
. by outdoor.npise.inthe majority.of the situations. However·, when people are active in the
. daytime, the hou:dy'equivalent sound levels have a range of over 30 dB, depending on the
type of activity; Thus; during the waking. hours, the outdoor noise sets a lower bound of
indoor noise. For the. outdoor Ldnrange of 52-65 dB this lower bound is significantly below
the averag~ level of the internally.generated noise.
.. :
EXAMPLES.OF INDIVIDUAL NOISE. EXPOSURES .. . .. ::"::'··
.. :.'.':'"
" . . . .
The noise ejcposures received·by iridividuals·ate very much a function· of the individual's
life.style. The variation in these exposures can· be :illustrated by examining .several typical ·
daily activity patterns. While these patterns. are realistic, they should not be construed as
applying to all.indivi~uals following .the particular life style depicted.
· .. Th~·total daily exposure, Leq(24)is considered the sum of tP,e sound ynergy from.all
daily exposure, including occupational exposures. Mathematically .this can be interpreted as:
Leq(24 br) ~ 10 log [ ~~~ ; X wL(ti)/IO 1-49.4
B-7
...
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·· ... ··-·.
··.• :·-~'------·~---. -:_7_ .. _ _._-. :~----.. -
.. ,·.:· ---~ .-. :. : ; .. : .. _.-_:_._·:: ..... ·
where: L(ti) is the Leq value for the a~propriate ~e p~ods, (tt) and the· summation of
. . .. , n .. , . _;. .. -. --__ . _,. -----.--
all the ~'s must equal. a total of24-hours {ie., Z ··tf=-24holirs($6400:sec.)); . ,. . . -. :· . · -··-·.::.··· . L7}:.·.·.:·· ··:~·;.-.·· .: · ··"=-;:~:··< __ .: ·.
Five different exposure patterns for a 24-hour day are depicted. in Figures :a~3 to :&-7. -·
The patterns are representative of the expos~es that might be incurred by;. . -
-. . --·-.... ·
. -~ : -·.:.
-·:·· Factory worker .-. __ ... . .. , Figure B;.3 . ·-···:·:., · · .. ·.-·: .. --
··'·:· ... ·.· ·.
· _ O.ffice worker.
·Housewife ·--· . ':.; -~!~ :~·-~ ·.:::j_. :-.: -~-....
· School chilQ-_ . _ •... _
: Pre-school cruld . ·
. , :.> ~ figure B-6 · . :~. _
·. Figure~T
.. ···: Certain assumptions were-made in· determining=· the levels· shown in ·Figure-·:&-3:.to B· 7 ,·
First, it was assumeq that the suburban:en~o~rnent was equal to anLdn of SO (Ld ='so,
·_ · Ln = 40). For the· urban environment; th~ tdn v,alue was 75 (Ld = 72; L 0 :: 68) .. The levels
_,·:··---
·-··' -.:-
. " . . .... . . . . l .
for the various actiVities were:deterinfued:fi:om previous EPA'reportson·appliance-noise, ·
transportation ·noise; as well as irifoririation contamed''m'the'·E:PAtaskGroup No.3 Report
relating to aircraft noiSe.B-4 · · -. -• .... · · · ..
Values for the Equival.ent Sound level (Leq(24)) experienced by the individuai are com-
puted from the basic formulation of Leq· For each of these lifestyles, the Leq(24) value and
the Ldn values are equivalent as the controlling noise dose normally d()es J10tbcc_lll' at night.
This emphasizes that for most pr.a.ctical situations, the average_ individual.Ldn. dose or Leq(24) _
individ~ do~ are interchangeable. . . . -. · · -· . . .. . -· _
... ~ :-
Noise levels for other lifestyles could also be generated. ,However; it i~ important to
remember that Leq(24) values are·, in most eases, controlled bY· the 2; to 3.,hour-exposures·
to relatively high level noise. For example, assume :a motorcycle rider rode<}ijS vehicle for 2
·hours a day at an expostire of 100 dB produciilgan Leq(24) of 89; if this-were :the case, then
other noise producing activities during the day would have little effect on the Ldnifthey
were at a level of at least 15 dB below the level of the motorcycle.
B-8
....... .·.·-
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FACTORY WORKER
a ..
...J
100
90
801-
70
Leq(24)
SUBURBAN ---87
URBAN ------87
nfl·. 1
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' 1 :
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rW I ,.-_ · ·lUI ------rJ-Let . ; I--
60
50 f.-.
40 1-
"' ... "'"' "' ..,,_ ..
30 a..· :si ., :> X
"' "' ::;; «
"" '::;; a: .... a: ::;; .... ...J
...J· ~0 ~-« ~ 0 «"" "' ... v .... <.> "'"' I I
12. 3· 6 9 12 ·3 s
MIDNIGHT NOON
0 3 6· ·g 12 1.5-18
. HOUR OF DAY ·
OFFICE, WORKERS
. ···r:r .... .....
-•.: .:,_ .. ·
l.eq(Z4J ..
SI:IBURBAN -.--·.-72
, .URBAN.--.-:----:-70·
. :.···
z·
0
\1i >·
"' ...J
"' ...._l
9
a..
"' .....
...J
(I)
12
MIDNIGHT
24
.. .... . -., .... ·-·· .. ;_--
:;;
·-.... ,. 60
50
40
.· .. ·
·-· ..
"' .a: ·-~·
-. ~-', .
9-:. ··.12· .3. ·.s .. ·
·g: ' III~N 15 .• is
HOUR OF DAY
...• ·:.= ..•.
9 :. 12
.. MIONIGI+T • 21 . 24
.··-··:··· .
Figure B-4.~ Typicai Noise_ ~xposute Pattern. of an Offi~e Wo~kerB;. 1 ,B-4,B-8 ,B-9
:--··.
B-9
·'.
.·.:,:,_:.:.
::-... · ..
HOUSEWIFE.
:t ....
80.
70
·60'
50
40
----...,;.--
.... ..... ..... .....
Ul
12 . l·
MIDNIGHT
. Q; ;~·.
s··
6'
· ....
:·• .. ··. ~ .. : ·.
:-::T~: .,~·:>~· ·.· -::..· .... ~...-:.-:
12
·NOON
9· ·. ·12 ... :IS,·:.: 18.
HOIJ~ OF DAY.
... <.·
12
MIDNIGHT ·ai .. z.;.,.
. ·. ··~ ·_ ....
:-;,';": . ... -... ... ·· ... :..·
··:'.-.'."
. \.,·
Figure B·S. Typical Noise Expos~e Pattern· of a'HousewifeB;;l ;B-4;B'-8 ,B"'9
SCHOOL CHILO
... .. ....
eo
10
60
....
.. . . . . '-tqcz•1 : .
SUatiF!EiAN'~ 71''
UFIBAt.l ,.: -' --: -'-2r7' :·
...... ···
-------
50
40
30 f::i .., ....
(I)
12 .3
MIOI~I~HT
0 3
6
6
9 12
·NOOI>f
9 12 15
HvUR OF" DAY
6
18
9
Zl
...
t::l ....
'"
12
MIONI(~._,T
24
........
Figure B-6. Typical Noise Exposure Pattern of a School ChildB-l,B4,B-8,b-9
B-10
·····:··.
. ...
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·';·'
PRE -SCHOOL CHILD
C1' ..
..J
so
70
60
50
40 .
30
Leq(24)
SUBURBAN ---60
URBAN -------69
r----,
I I
I I
I I
I I
(/)
0:
0 .... 0
0 ::;; ...
0 ::> :I: 0 ..... .....
~ ~ ~
..J ..J 0.. .... 0..
6
6
9 12 .3,. 6
-NOON
9 12 1~. 18
HOUR OF DAY
·.--· ....
9 12
MIDNIGHT
21 24
Figure B-7. Typical Noise Exposure Pattern: of a Pie-School Child
B-1, B-4, B~, B-9
. ' .. :
••• < •• • ·.·::. ·.,~
B-11
· ...
·· ...
Reproduced from
_best available copy.
'-.· ..
.. ~· ..
.. · B-:1.
B-3.
B-4.
.. · .. ,
····· ...... . · ..... · ....... :
. ;.. .. • ......
... ··,. ···.·.
··.·.·.
Eldred,K.M.,. "Community Noise;' Environmental Protection Agency NTID 300.3,
December 1971. ·
Garland,.~.L,Hanna,SJ .. an.dLamb;D.R.,''AlllbientN?ise;,WindandAirAttert-
tuationin Wyoming," Proceedings of Noise-Con 73, Washington, O.;C;,October
1973;
·· ...... ·
Bolt Beranek and Newman~ Inc.~ ·~survey of Annoyance from Motor Vehicle ..
Noise,'; Automobile Manufac:t;w:e:rs A~~i9~t Ip,c;~ Report ~lJ2:,. JWte }971 .
. "Impact Characterization.ofNoise IncludingJmplications ofldentifying and
Achie$g Levels of Cumulative Noise ExpOsure,~'. EriVironmental Protection
Agency NTID.73.4~ July 27, 1973.
B-5. Galloway, D. and Eldred, K., 100'-Site ·RepOrt, in-preparation as a BBN Report
for the Environmental Protection Agency.
:s.-6. "Report to the President and Congress on Noise,'' Environmental. Protection
· Agency·NRC 500.1, December 31; 1971.
B~7.~ . ''House Noise -·ReduCtion Meas~ements for Use in Studies .of Aircraft Fi}·over
· Noise/' Socie~y of Automotive Engineers, Inc., .. AIR 1081 ,,October 1971.
l\.-8·. · "Transportation Noise and Noise from Equipment·Powered'by hlternal Combustion
EngineS, •·• Environmental Protection Agency: NTID: 300~ 13, December 1·97'1.
''Noise from ConStruction Equipment and· Operations~ Building Equipment and
Home Appliances," Environmental Protection Agency NTID 300.1, December
1971.
B-12
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. ~--' ~-~ .. . . -~·· .. • ..
. ,. . . . . . . .. ~ ... .
.··, .
.. ···.·.
.. :··· ·.
APPENDIXC
NOISE~INDUCED HEARING LOSS
.... ~ . ·, ' .. .·•·.· , .. ··.·· ·. .. . ..
. : . : . -~ . : : ' ....... . . . ,· ..
·.·······.:·
··.·· , ... ·.'
.,•.:.·' ··:···· ..
--. (!.;<.-l . . . ·•. :
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APPENDIXC
NOISE-INDUCED HEARING LOSS
INTRODUCTION
A considerable amount of hearing loss data have been collected and analyzed. These
data include measurements of hearing loss in people with known histories ·of noise--exposure.
··Much of the> analysis consists of grouping these measurements ·into populations. of the. same. · · ·
age with the same histocy of noise exposure and determining the percentile distribution. of
hearing loss for populations with the same noise exposure. Thus, the evidence for noise-
induced permanent threshold shift can be clearly seen by comparing the distribution of a
rioise-e~posed population with that of a relatively non-noise-exposed population.
.. · .. :-
Most of these data are drawn from cross-sectional research rather than longitudih:al
studies .. That iS~ individuals -or populations have been tested at only o~e point k tiine. ·
Because complete noise-exposure histories do not exist, many conclusions are limited by
. ' : . :~ .'
the need to make certain hypotheses aboutthe onset and progression of ~10ise-induced hear-
ing loss. Different hypptheses about the time histocy will lead to different conclusions even
from the same data base, although the.range of such conclusions is limited. Thus, in reaching
. conclusions about hearing loss, reliance is made on assumptions, hypotheses, and extrapolations
which are not all universally accepted by the scientific community. However, attempts have
been made to consider differing opinions and to insure that the methodology and:conclusions
in this section are in the mainstream of current scientific thought.
BASIC ASSUMPTIONS AND CONSiDERATIONS
In order to proceed further; it is necessary to make the foil() wing well~ based assump-
tions:
· ....
1. Heari:iig shifts in the "non--:noise-exposed"populatiop.s are attributable to aging··
and other eausesrather than .to noise exposure. --·· .. _,. . . .. .... . .· . :. ; .. . .
2. As individuals approach-the high end of the distribution and their hearing becomes
worse, they become less affected by noise exposure. In other words, there comes a point
. where one cannot be damaged by. sounds that one cannot hear; . . .
C-1-~
.... ...
.. , . . . : .. -..
;: ..
.. ·· ·;.
·, ·:·' ··:·
.. _,_· .....
.·.-· ..
In addition, there are some ·important consideraticins:ne~ssary for the iden tificatiort of
· a levelto protect against):1earing lass.-· · · · . . ·. . . ···.
. ....... -.···. ..·.· ''··· ..
:: '·'' ': .,.;.
. . . ' ' . ;
Preseryation.of.High Frequency''Heanng. ... ·.:-:::.:·: . .",•;·":•'·'';'.····
. ·, ~ . . . .. . . , .. :; . .
·. :·· : . • . ~.·: :_. -.. • .·: • . . • ! . • .••..
The leVels identified fu this do.Cuinent for h~itting ~-cinServation purposes' Me those which
. have been shown to_ provide protectionfrom·any_,measurable.degradation-.ofhe~ac~#y~-·_·· ..
. · Trus·protection'is provided even forthoseportion~·ofth~ hearmg mecharusm whleh-resp~rid .
to the-audiometric frequency at which noise-induced hearing impairment ftrst oc;curs, namely ·
40()0 ~· The defmition of hearing )Ja,n(iicap Origb.late~i ~ytbe Anlerica,ri A¢a~mY·of0pthal;. .·
. mology and Otolaryngology (AAOO), ~d currently in~rpo,t:ated in mariy bearing damage-· · , ..
'· risk criteria, is somewhat-mffe@.nt .fr.Oiil.-the defmffim~·-tlsed:jn tlili''document;: H~g han eli-..
cap, (and later, hearing imp~ent) \Ya5:defiri:ed ~Y afonnula which ~d_tfie:,ayerage ·heariJlg. __ .
level at s 00 Hz, ~ 000 Hz· and, 200.0J~i;. ::;: · ' · -~-:~ · · ... .. ! ·--· · -· .· · · · · · · ·· ·
Although hearhtg loss fot frequencies abo\re 2000 Hi~ llot trea;ed -~signifitant by
mosto.f the existing occupational hearing darnage;;fiSk:ciiteria·, the ability t6 heat frequencies
above 2000 Hz is important for understanding speech and· other signals; DeSpite the traditional
use of the terrtt "speech frequencies•• to ~pply to· 500~ 1000 and 2000 Hz, useful energy in
speech sound ranges from about 200to·6l00 HzP·l It has been known for many years that
the equal discriminability point in the speech spectrum is at about 1600Hz. That is, fre-
quencies above 1600 Hz are equal in importance' to th()se: below 1600 Hi. for understanding
. · · speech.C~l However, there are other reasons for pre8ervmg the frc;~quep.cies above 2000Hz.
Higher frequencies are important .far the localiZation and. id.entificatiall:of fam~;',hiih-pitched.
sounds in a variety of occupational and soci:al·sitiJations. Detectian·of~oft;,relatitely' hiih~ · ·'
frequency sounds can be espe.cially importantin<yi~~ce·:.tasks; such,a~ tll()se-Which may --
occur in the military. In addition, good. hearirig for. the higher f~eqiiehcies-Js impoitazlt to,.
heai everyday occurrences such as sounds inditlitive .of deterioratiOn in mechanical equip.. .. _
merit, crickets on a summer evening; bird sOng, and·~· muSicai soundS; In fact;·b.igfi-·· .
fidelity sound reproducing equipment is often promoted on the basis of its· rldelity up to
15,000 Hz, or even 30,000 Hz.
Any measurable hearing loss at any frequency is unacceptable -if the .goal is protection
of health and welfare with an adequate margin of safety. For most environmental noise;
protection at 4000Hz will insure that all other frequencies are protected.C-2 Thus, the 4000
Hz frequency has been selected as the most sensiti_v:e indicator of the auditory effects o.f
environmental noise.
C-2
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Significant Changes in Hearing
In this section an attempt will be made to.determine the relation between exposure
level and noise-induced permanent threshold shift (NIPTS). Before this is accomplished, how•
ever, the significance of various amounts of NIPTS needs to be addressed.
For the purposes of identifying the levels in this document, it was necessary to adopt a
criterion for an allowable amount of NIPTS. Whereas a NIPTS of 0 dB would be ideal, it is
not appropriate for the following reasons:
1. Most audiometric equipment does not have the capability to measure hearing
levels in less than 5 dB steps.
2. · There is no known evidence that NIPTS of less tha11 5 dB are perceptible or have··
any practical significance for the individual. ··
3. Individual hearing thresholds are subject to .minor fluctuations -due to transitory · .:.~.'' ·.
~ . . . .· . . .
. . psychological or physiological phenomena.
. . NIPTS of. considerably larger amourits have been permitted in vanous d~~ge .. rlsk cri-
teria in the past. For instance, shifts of 10 dB to 20 dB have been considered reasonable.C-3
However; the requirement for an adequate margin of safety necessitates a highly conservative
. approach, This approach dictates the prevention of any effect on hearing, which is defined
here as an. essentially insignificant and unmeasurable NIPTS, i.e~, a NIPTS of less than 5 dB.
The available evidence consists of statistical.distributions of hearing levels for populations at .
· various exposure levels. The.evidence of :NIPTS, then, is the shift in the statistical distribution .
. . . : .. of hearing levels for..a noise-exposed population in comparison to that of a non-exposed pOP:" .
.. ··_··• ·uiation .. ,·.-:· ··.··.-~,
.. ,··
-:····--.:-
PREDlCTION OF.NOISE-INDUCED PERMANENT THRESHOLD SHIFT
Stahis of Hearing at 4000 Hz in the United States ... ,;· . . '·;. _.; · .
Figure C-1 summarizes hearmg levels: of 'the gener~l U.S. population .. ~t 4000Hz. The data
ate from the Public Health Survey (PHS)conducted in 1960·62 in the United States. C:~ · ·• ·
Robinson'sC-5 non-noise-exposed and otologically screened population is shown for compari-
son. Several points should be noted·:
C-3
·_:.··.
... ,
~:··. . ' . ·: ... ~.
.. ;. --.
0
"'
-~
<D
.. 2:0-.
~
! 30
:::.··
...J
~a:t w-o·
...J
C!l -40·:
z· a:
<(
50 w
l: ·.·-.....
60
90 9-8 99:8'
95 . ·9-!h-· ··99;9.:.•·. ··· ....... .-.. :
WORST HEARIN~ .
POfiUL;ATION PERCEN'TILES •. · :::;· ..
1. The hearing of a selected percentile of the population can be determined for various
age groups. As displayed here, the.-higher the percentile point, the worse th_e hearing.
2~ At age 11, there is no hearing difference due to sex, C~ but for the· 18 .. 24 age group, .
. a· definite difference is evident, with men's hearing considerably worse. · . · .. · ... ~. .. . . ..
3. Considering that there is no ~vidence for any sex~inherent differences iJ1 susc~PJi~
· bility to-hearing iliipairinent,.it is most likely that. the. differences displayed ~ due· to noise ; . .
exposure.
The Effect of Noise on Hearing
Table C-1 summarizes the hearing changes expected for daily exposures to various values
of steady noise, for an eight-hour day, over 10-and40-year periods.C~7
Four different measurement parameters are considered in Table C-1:
1. Max NIPTS: The permanent change in hearing threshold attributablt· ~o noise.
NIPTS increases with exposure duration. Max NIPTS is the Laximum value duri".; a 40-~:ear
C-4
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Table C-1
SUMMARY OF THE PERMANENT HEARING DAMAGE EFFECTS
EXPECTED FOR CONTINUOUS NOISE EXPOSURE AT
VARIOUS VALUES OF THE A-WEIGHTED AVERAGE
SOUND LEVELC-7
Max NIPTS 90th percentile
NIPTS at I 0 yrs. 90th percentile
Average NIPTS .
Max NIPTS I Oth percentile
Max NIPTS 90th percentile··
NIPTS at 1 0 yrs. 90th percentile
Average NIPTS . · .·
Max NIPTS lOth'percentile· .
. Max NIPTS 90th percentile
NIPTS at l 0 yrs. 90th percentile
Average NIPTS ·
Max NIPTS lOth percentile
Max NIPTS .90th percentile
· NIPTS at 19 yrs. 90 percentile
Average NIPTS
·.Max NIPTS lOth percentile.· ·
75 dB for 8 hrs
av.0.5.I.2 kHz av.0.5.1.2.4 kHz 4kHz
I dB 2 dB 6 dB
0 1 5
0 . 0 5
0 0 0
80 dB for 8 hrs
av.0.5.1.2 kHz av.0.5.1.2.4 kHz 4kHz
I dB
I
0
0
4dB
3
1
0
85 dB for 8 hrs
lldB
'9
4
2
av.0.5;l;2 kHz av.0.5,1,2;4 kHz 4kHz.
4dB 7 dB
2 6
I 3
r· 2
· 90 dB for 8 hrs
av.0.5,L2 kHz av.0.5.1.2.4.kl!z
7·dB
4-:·
3 ..
2
12 dB· ·
9 '.
6
4'
.19 dB
16
9
.. 5
.4kHz
28 dB
2.4
.IS
ll
Example:.· For an exposure of 85 dB during an 8-hour working day, the following
effects are expected:
C-5
·. : ....
,,· ...
... , :;.:·,.
-expositre _that starts at age 2o. Data f~oiQ. the 90th; perc;entA~-poinfof.tl).e·popula:tiqn wi)l~e _ .
·used to extrapolate to highe:r.percentil~' · -'· ··--• .... _.. ·' •·: :-·'· · ,;_ ... · .,. ·· · --
... ··; .. : .. ·.·.·· '.··.;
... _. 2. _ _NIPTS ~t I 0 years: The entries on tlUs row a~o-apply;.to .the·9ot~_pef:centile-point·.,
of the population for 10 years of exposure. --------
.:.'·
::· ·.
_ 3. Average NIPTS: The value.of. NIPTS is av.eraged:.over all tlle'percen.tiles:for aU age · ..
· groups. (This figure· differs by only a C01lple of decibels from. the m~dian. NIPtS after 20· ..
years ofexposiu-e . .for the entire' populat:ioh.) · · · · · ·-;.. ··.·· ::,: ' .·. ·
.•.;> .
-The values in Table C-1 are arithmetic averages of data found iri ·th~te:ports.ofPasschi~r:-
. · Vermeer;C-8 Robinson,C-5 and.Baugliii.C-9 .. -·.-· · · · · : . ..-. --·-: ---_ -. ~-. , ·
·· ...... . ·.·.: .. ·.· . ,,;:·::· ,.... ·.,:.-:.:.:·::·:; .. ;:
DERIVATION OF EXPOSURE LEVELS,
Selection of the Percentile and-Related Exposw:_e Level. ..·· ..... ;.;
-· ··.· ....
The estimation of NIPTS for a given percentile has been .aceori:iplis~d by .subtracting
· .. · .. the -hearing level of that percentile· of-the ·non-noise-exposed gr6up from'the hearing level Oi
the respective percentile of the noise-exposed group. People above the90tlrpercenti~·ar.f}~ . -_.
those whose hearing is worse than that of 90 percent ofthe··populati,on: -T-liu$; for:exampie; _: .. _:.-
-if the group at the 90th percentile sh<>ws a shift of 1 0 dB because of noise exposur~, then it .
. is considered that the group hasa NIPTS of 10 dB. Extrapolations abOve the 90th percen-
tile can bemade from existing data, as done in Figure C-2. These extrapolations require
cautious interpretation. First, the data for the 75 d-B exposQre levels in Table C-1 are them-
selves derived from extrapolations. The last rum data areat 78 dB. Second, for many ofthe
studies that serve as the b~Jo.r ~he.. Passchier-Vermeer work, the 90th percentile is already
extrapolated from the 7Stii percentne:
As stated earlier, the assumption has been made that if a person's hearing loss is severe
enough, noise exposure will not make it worse. To be more precise, a persor. will not incur
a hearing loss from a noise that he cannot hear (so long as it is within the audible frequency
range). Granting this assumption, it follows that at some percentile, the amount of NIPTS
C-6
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TTrr 1-r-·r-T:rr. -T-·fR 151--i----1---+--+--T-r----r---r---i -·r--_-.t:-1 -n----t-~
I I ; ' I J ).'/ I i : ; • • I . ' ! I
• I 1 ·-I I I I i . I I ·1' I 1 · . ; i · i ~ y· ; i ! ,
I; '. y: ! 'I I; 1 ! . ! I . : /: : I I i . /1' . I 1 · · .-. ' : : , ! . ,
j i ; 35~8A / i i J : ! / J
I 01-i----!----r·---r--:-y· ~---~--+-..:..l--L~----t----1
! 1 i i ': l i :': I
'I I : I . : : . i / f ! :
1 ; / : i / ; l l
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: i i , I i II I I I ' . , I . . I . /t . I 75·oBA -"--f--1 INTERPOLATION ---
.......... / ' ' : r 1 ; SINGLE I
. I :}"'1 I 1 EXTRAPOLATION ____ -I : I I I .. A I : I ·I ' .·.· . ' . ! . !..-I I I ·. I • 1 ; · 1 ' ,, 1 , I DOUBLE __ _
i 'i : l i l-,.1': ; : ~·· .,EXTRAPei:.·ATION i I ! ' J:.: --~~-~-J ; i ! I / I _: I I . ;_ . . __ ... _-f':"~. --: ~' -~ ... !.,.__._l.__.;___~----------~-L..--. :-_.J
I <~ 5 10 20 30 40 o;Q tiC 70 BO '30 95 ')8 99 ~~8 <;t9.9 j9,S!:!
PERCENTILE
. . .
Reproduced from
be,s.t available copy.
Figure C-2. NIPTS at 4000Hz across Perce~tlles for Varlous 40-yr E~posure Levelsc.:2
for a given e"posurelevel will approach an asymptote. In order for further hearing loss to be
incurred above this Critical percentile point, greater exposure levels must occur. In the
extreme, a person who-is totally deaf cannot suffer noise-induced he~g loss ..
A study of the data provides·. a. basis. f-or a reasOnable estimate of this critical percentiie.
Baughn 's.data gives.an indication that the population with a hearing level greater than 60 ·dB ·
after a 40-ye'a.r exposure begins.to becomeless affected by noise (Figures 9, ·10~ and il·of -.
· ref. C-2). For. example, ifa person· has a hearing loss greater tha~ 75 dB, it is not r~asonable
to expect tlul-t an }\,•weighted-noise: of 75 dB (which normally means that.only a level of 65
·dB would be present at the octave band centered at4000 Hz}will cause a further increase ... ·.
of the 75 dB loss. Next, it is necessazy tocdeteimine the distribution of hearing .levels. of the
rton~nois~-exposed.populatioliat age·. 60~.The best data available are the hearing. levels. of 60 ·
· year-old women. of the·l.960...62··Public Health Survey :C-4 While certainly some of the: .. ·
women .in the ·sample inay be ooise··exposea, the noise -~xposure of that popUlation sample · .. · .
ean·be corisfderedmfupras comi.u-ed to·theapparent noise exposure ofmen.The-datafrom
the Public-Health suiv~y predict .the percentage of the population with hearing :levelS above
70, 75, and.80 dB.
Figure C:-3 shows the exposure levels. at which no more than 5 dB NIPTS at 4000 Hz
. will occur for various· percentiles on the lowermost curve. The curve labeled PHS-4000Hz . . . . . . -'
C-7
.. ~, . ;. . ' .
.. :.··· .... ··· ..
80· 85
-... ·.·•·.· .. :··=.·:·
9o
'PERCENTILES·. ·.·
·. ·., ......... ,
. ~· .. ~ .. ·:.
': .. ::·-·-.· ..
100
· .... · . ·· .. ·;.·:
Figure C~3. Exposure Level and Hearing Level as a Function of Population Percentile,
Showing the 5 dB NIPTS Curve Merging with the PHSAOOO Hz Curve
represents hearing levels by percentiles of the non'-noise exposed populat~_c:m.~ lf.a.noise level
· that cannot· be heard by an individual iS assumed not to change his hearin,g level,. then. the
extrapolated 5 dBNIPTS curve of Figure·G·3 cannot cross..the;cmvelabeled:··PHS;.In fact~
the 5 dB NIPTS curve must turn upward and merge ~th. the. PHS· curve; shown,· iii. Figure ·
... . C-3 by the dotted line. The p~~t of merging is s~·J() b~ at:approximate1Y:th~·Q6th.per
....... ceritile' and· the exposme le\rei required to:ptotect this .petc~ntue from a shift ofniore :than
5 dB is an Leq(8) of 72 to 74 dB, or approx1mate1y-73·dB~ It may be:·conclu~e~ !herefore;:
· that a 40-year noise exp.Osure below an Leq(8) of 73 is satisfactory to pre.veirtthe entire
statistical distribution of hearing levels from· shifting at any point by more than 5 dB. Gen-
. eralizing from these conclusions, the entire popuiatiori·exposed to Leq(8)of7JiS·protected
against a NIPTS of more than 5 dB.
A similar analysis can be made for 5 dB and lO dB NIPTS at the mid·frequencies
(Figme C-4). The upper PHS curve represents the better ear data for the average of 500,
1000 and 2000Hz of both men and women from the Public Health Survey.C-4 Both men
· · and women are used since there is little difference due to sex and hearing levels for these·
frequencies. Considering that the curves will merge in the same ma!mer as the S dB at 4000
Hz NIPTS and PHS curves, one -.;an conclude that:
C-8
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...J 100 w 100 > w
...J
w a: 90 ::l en
0 Q.
X w
~ 80
<(
0 a:
J:
~ 70
a: >
0 ..,.,
60
..._ AV, 5 7 PHS (Av •• 5, 1, 2KHz)
Av • • 2KHz 7 v --r-...:...:.s. 7 2 I ' 0 d8NtPT • kHz 5 ,_ S .J!
~~ . ~~~~~~----
r--40oo r-"
-..:: Hzsde . ~~o....
. r--NtPrs K j ~~ . . r-._
r-
l.bs (4000 Hz)
1
-~ r--. I. .• 0.
I
:C::t: mm
...,J> o:c so ~z ~~
80 i~
"' "" ::t:
70 "' ·n c ·:c < m
60 en
1 2 5 10 ' 20 30 40 50 60 70 80 90 95 98 99 99.8 99.9 99.99
:,·. P:ERCENTit.ES ··•·. ·
Figure C-4. Exposure Level and Hearing Level as a Function of Population Percent
Showing Merging of Different NiPTS Curves with PHS Curves
'
1. · Leq(S}of 84 dB will cause no more than a 5 dB shift at the critical percentile for
the averaged frequencies 500,1000 and 2000Hz. · · .
.:.; .. , .·;. ···.·.·
. 2. hq(8") dB will cause.no.more.than a 10 dB shift.at the most critical.percentile for
the averaged frequencies 500, lOOO·and 2000Hz. ·
Although the data base used here is quite large, we cannot be absolutely certain that it
is representative of the whole population. Any argument such as that presented above does
not, in fact; provide 100% protectionofthe entire population: Obviously, there are a few
individuals who might incur more than ·s ·dB NIPTS for an. exposure level of 73 dB. There is ·
the possibility' thai individuals might shift from lower to higher percentiles with a change in
exposure level. In other words, there may be individuals-:who experience greater shifts in
hearing levelthan. those. predicted. here· over periods of. time much less than 40 years~ · . . . . .. ,.. · .. · · ... · . . . . . ..... ·.
At this. point; it may be useful to· examine the 'same data in a slightly different way,
. . . . without utiliZirtg· the concept o(tlie. Critieal percentile; As~timing .that the NIPTS. ofthe
exposed population are. dist:ributed.nonnally, the exposure levels .which produce various
amounts·Of'NJPTS atthe 50th.and 90th; percentiles may be extrapolated to.h:;vels which ·
. · produce NIPTS att}1e 99th percentile. ·Using lhis.extrapolation, Figure c.s shows NIPTS as
C-9
. . . ·: ....
···.-·'··.·: . ··••.
... ,: ... ;··:::, .'
.;-;.-··;
... :-::· _, ... ·-"'
·.·'.',.•··:.·.· .. ·
..... ·,· . .. ·-· .....•. ;
·. ·.·.~ ~ ·:::. :,.. : :: ...... ·. :: .. : ... : · ...
··: .. :_.:,-.···
.. : .. ~ ..
· .... ·''
.. ~-:~
...
··.·····,·
I!IS· . 7D "" ..
.. ~ ; ·:··= .. :
··Figure C~S. · NIPTS as a Function of Exposure Le.Vel for the 50th, .
90th and 99th Pereentiles ·· · · · · .
a function of exposure level for the 50th, 90th and 99th percentiles. The 99th· percentile
.. : ... curve intersects the 5 dB NIPTS ppint at 71.5 dB.(:w.l#c11 is ()~lyJ.·5 dll ~lo.w.cthe::level pre-, ., ....
· .·· ·· .viously identified). Thus, if one wishes to protect up to the 99t~_per~ntue.~~t}f.ou~. employ-....
. . ing the co~cept of the critical percentile~ the exposure level nb~ssary to pr~ve~t more than
_·. S dB'NIPTS is an L~(8} of 71.5 'dB-. . ·· '· . . . . .. • ·. ... . .. . . .. .. ___ .
·.: · .... :.
The preceedinganalysis utilizing the conceptof .. the cri-tical·~centile.,.,(?Oll..cludes,.·that ~:, .. :( .. ,,
8-hoUr per day exposure-to a 73 dB steady noise.'for 40 years will festiit in ~:nois~indil~d ::;:: · · ·
permanent threshold shift of no mote than 5 dB at 4000HZ~ ThiS concluSiOn' was teacbed ....
through the use of assumpti6n5 and considerations pointed out e.arlier lll this. app.endi.X. Siliu-..
lar analysis of the sallie and similar data maybe made usmg other assu.mptlons and conSider~
ations. Some analyses lead to essentially the same conclusion while others do not. However,
no such analysis has identified a level of much less than 65 dB or much greater than 80 dB
for the same conditions (i.e., 5 dB NIPTS at 4000Hz for 40 years of exposure). While the
discussion of these levels and their derivations are a subject of great interest and activity in
the scientific community; the Administrator of the Environmental Protection Agency is
required to identify the level which, in his judgment, is requisite to protect public health and
welfare. For that purpose, the level of 73 dB appears to be the most reasonable chuice for
the conservation of hearing based on the present state of scientific knowledge.
C-10
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Adjqstments for Intermittency and Duration
The next step is to transpose this level into one which will protect public health and
welfare, in terms of environmental noise exposure, with an adequate margin of safety. For
this purpose, it is necessary to correct for intermittency and to extrapolate to 24 hours. In
order to do this, two hypotheses are necessary-the TIS Hypothesis and the Equal Energy
Hypothesis.
The TIS Hypothesis states that a temporary threshold shift measured 2 minutes after
cessation of an 8-hour noise exposure closely approximates the NIPTS incurred after a I 0-:
to 20-year exposure to that same level. There is a substantial body of data supporting this
hypothesis. ·
. The Equal Energy Hypothesis states· that equal amounts of sound energy wili cause
equal amounts of NIPTS regardless of the distribution of the energy across tim~. While. there
··~s experiitiental corifl.Illlation andgenerafacceptance·of this hypothesis, ~rtain types of
intermitten-cy limit its application.
IntermittencY. .
. The equal energy concept is considered by some to be a conservative approach for;
short exposure periods. An alternative approach may.be necessary because there is little
direct evidence to show the effect of short exposure periods or intermittency on the develop-
. ment of NIPTS. This .approach implies the use of temporary threshold shift as a predictor of
NIPTS,
Even for a continuous noise, TIS is not predictable for all possible durations using
the equal energy rule. The equal energy rule' predicts, with reasonable accuracy, the Tis· at
4000 Hz fordurations of 8 holll"S" 'down to about 30 minutes. Effects from durations shorter
than this, however, are better predicted by a slight deviation from the equal energy rule.
While ~qual·energy pro~des for. a 3 dB increase in exposure level for e~ch halving of ex:Posure
duration, TIS for durations of less than 30 minutes are better predicted by greater intensities.··
for each halving-of time. For instance, TIS for durations of less than 15 minutes are better
predicted by a 6-dBrather than a.3 dB increase. For an exposure of two minutes.duration,
the level required to produce an expected TIS at 4000 Hz would be approximately I 0 dB
greater than the level predicted by the equal energy concept..·.
.· . Investigations of environmental noise patterns reported in the EPA document ·. · · ··
"Community Nois~" c~l 0 indicate that in most environments; n6ise fluctUates or 15 inter-
mittent. Moreover, intermittent.noise·.for ~a given Leq having peak levels-:1f 5 to .15 dB
higher than the background level; may-produce less hearing: damage than a continuous noise
C-11
·· .. ········
.. ·~ .... :
: ... , ····· ·:·
.. with the same energy.C-ll Also, noise levels which·are:below 65 dB for 10 peicent of the
.time tend to. be lessdangerousthan contiinious noise:C-12 Therefore,.'.interniittertt noise a5
:used in this document will be d~fmedas·-noi8e which ·is below 65 dB for aboutJOper(:ent of .
each hour (i.e., L9<)-ofJess than 65 dBkwith peak.l.~~ls ()f.'S:.~<J.JS· dB'~~~~-i~J~IT:the:bac~-. . ·
ground. From the examples ~cited iii ~·cqmmWlity· N.OiSe"~ ifiS dear tha~ ·most envitonmental
noise meets these· criteria. For this. reasori.,. the Leq' me~uied iii lriany situa tjons can: be : .
· e)(pected. to produce.less harmfUl effect$}:lD hearing._t.h.,i41. tho~e:depicted iniTa-ble :c_-1. ~9mtl.·
co~ection= factor is·thus·indicatecl ,fqr Leq·'•alues· describing noise expected·. ina··typ.ical
enviromnental·situation in which the e)Cp<;>sure is relativ.e~y :int.ense. but; iilt~rnrl,tteJ1t::in: pa ture~·' : ..
. . • . "• . . .~ . •. . • .""· .; • •. : . '. • ;" ·.. . ·: . .". :·.:·':· . ~· .• ;.. . • • I • ... :
.. ·. . lh::order to deterlnine an appropriate correction factor, Figure Ci6 has been dra~~;
.. Using an exposure of 73 dB for 8 hours a,s a baseliiie,,_the .sound pressilreleve1s. producirig . '
· ~qualTTS2 to be expected at4000: Hz ar~:p~otted ·.fQr duratio~s of continuou~ noise as.sh()rt
·. as.l~·l/2 mmuteS. C-3' ·Plotted·aiso=(curve'a)~··iS th~ iilaximurii,mterinitten_cy·correctioiisug-. ·.···
gested by ."Secondlntersociety Committee" C-13 imd discussed iii. the' NIOSH. criteria d ocu-
. ment.C-11 This correction is forthe mid-f~quertc,i~:·Recentwork hasiildicatedthatfor · .•. ·
4000 Hz the best interriiittency correction to produce-eqUal TIS1 is represente_d by cUrve . '
. · .-b.C-1 ~ The crosshatched area between the eurves:. ~'a"'and ~'c" signifie~ ~?~ ~a of u!l~~rtain ty.
;........ . .. ·.· ·.··,.-·
.. -'···· .. . .... ·-:.· .:.,-
·········.
··.• .. :.;: I .. -~·· ... . ... · ...
i w
a· · 1
... HAS:·' .SEC
TIME. · ... ··.
•· With 5 d8 correction for intermittency added.
NOTE: lmpulse·noisa is defined as Leq;-PEAK -9 d!L Shaded area·indicates·area of uncertainty.
Figure C-6. Equal TIS Curves for 4000 Hz·
C-12
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In addition, TIS curves. for impulse noise are included in Figure C-6. Appendix G
contains the details of the modified CHABA limit and the conversion necessary to derive from
the peak sound pressure level of a decaying impulse the continuous A-weighted noise of the
same duration. The impulse noise data show that the equal energy concept is still a reasonable
approximation for very short durations. While certainly it may be overly protective for some
noise patterns, in general it predicts the effects of noise on hearing reasonably well. Prediction
is improved, however, with a 5 dB allowance for intermittency.
The average correction for intermittency sugg~st~d by Figure C-6 is· 5 dB· (i.e., plac-
ing the origin of the equal energy line at 78 dB for 8 hours). This correction should be used
only if the noise level between events is less than 65 dBA for at least 10 percent of the time
(L 90 < 65 dBA). Since most enVironmental noise exposures will meet this requirement dur-
ing· any 8-hour period, it is further suggested that environmental noise should be considered
intenruttent unless shown otherwise. Using the 5 dB corre-ction factor; the area of uncertain"ty":.
·(crosshatched) of Figure C-6 is appro~ately bisected. Further support for such a· S"dB cot--. · ·
rection f~ctor is found in a recent Swedish study where exposure to continuous noise of Leq ..
85 to 90 caused a hearing loss which corresponded to an intermittent noise·of Leq 90 to.95~ ·.
The authors: conclude that a 5 dB .. correctionfactor is appropriate. C-J 5
For certain noise situations, aJarger intermittency correction might be justified.
However, the us~ oflatge corrections when only part of the total noise exposure pattern is
.known entails a considerably higher chance of error. Therefore, the use of correction factors
higher than S dB for intermittency are not considered consistent with the concept of an ade-
quate margin of safety.
...
Conversion .of 8-Hour to 24-Hour Exposure Levels
The TIS after 24 hours of exposure generally exceeds that after 8 hours of exposure
by about 5 diJ.C-2 Thus the use of a 5 dB correction factor is suggested to extrapolate from
the 8-hour exposure data to· 24-hour exposure.C-2 For example, the predicted effects.ofan
exposure to 75 dB steady-state noise for·a 24-hour·d~tion are equivalentto the eff-ects
estimatedfrbm industrial studies for an 8-hour exposure to a continuous noise with a level of
80 dB. This,S dB ·correction is consistent with the equal-energy trade-off between exposure·
. duration and noise level. That is, the equal-energy rule.in.this case also dictates a correction
of 5 dB for·24 hours ..
. · It appears that exposures over a period longer than 24 hours need not be cot1Sidered .
in this case. Various studies of TIS C-16,~-1 7 ;C-.18 have sho~nthat, for CU1 e)(;posure to a .
specific noise level, TIS will not ~xceed a limiting value regardless of exposure dumtion. This
. limit is reached at approximately 24 hours of exposure. However, this concept applies only to
· exposure levels less than 85· dB .. · · : · .. · · · ·
· .. · .
C-13 ·.•:
.:, ... ·
Conversion of Occupational Dose to·a Full ~ear (2SO:to 365 Days)
..
. The applicability of o~upationa_l d·ata to ~~~-o~UP.::tY.onal eJ{posure is questional
in several ways, One concern is the use oftlie occupatlonal·exposure d~ta to predict the
.. general effects '00 populations compO$ed; o_(people ~ll9~JQr ;a~y_arlety of:reas<>ns, do nOt work.
However, there are no data froni. which i(; derive approximate co~cti~n fat:tors~ An9ther
concern is the ·fact that the occupational data are based' on··a· 25o.day working year~ When
predicting the effect of a known noise ~xposure over·the 3()5-day year, -certainly some cor-
.. rection·is iri order. the _equal energy concept. would predict ·~t Ieasfa.l Ji dBJowering-of the' ·
.. :.,exposUre level, and such a correc_tion shoUld be used:~b~J1.~tb~--~~ceptp(.~ aDJ1UaLexposure
· ';. dose. is used. · ·· · · .·. · · · ·. . .· . · ·•.·> .
To sUrlunluize .the a,dj:qStmen·ts, .the..foll~'Ying·:expf?sureS. 9ver.40)~e~ww: resultiJ1.
· :the same·eff~(:t: . ·· '... ··· ... · · .... • ·. .. ::;; .: · .. <.(~: .: .•. · <, ·· .. :·· . ·~:-.. ·
•
. . . . . . . .. . .. ·.·
Leq of 7.3 .dB· continuous. riolse• durlrtg the. 8-hour-working:daj/ .·. ·• .· ....
with relative quiet for the refua.iningJ6 houis, 5 days per week .. ·.
(See discussion ofquiet reqwrementSbel6w}. · · ·
.. ;···· ···· .. ·
• . Leq .of 78 dB inter.mittent·noise. during the,s::.hour \VOi'king d'ay····
with relative quiet for the remaining l6·hours, 5 days pet:week. · . . . •.--··
•
•
73 + 5 = 78
::' ' .. -Leq of 76.4 dB intermittent noise for s~hours a: day, with
relative quiet for the remaining 16 hours, for the·365-dayyear,
78 -1.6 = 16.4 . . . . . .
Leq of 71.4 dB intermittent noise for 24 hourS a day, 365 days .··
a year.
76.4-5=71.4. . ,,:,:··. . ........... .. . . :../:
. : .. :. ~ : ' :.
In view of possible uncertainties in the analysis of the data, it is considered
reasonable to round down -from 71.4 dB to 70 dR These uncertainties will be discussed in
the next section.
CONSIDERATIONS FOR PRACTICAL APPLICATION
The Data Base
In viewing the data in this appendix and elsewhere in the hearing impairment li~era.ture,
a number of fundamental considerations must be noted:
C-14
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1. Few, if any, of the various "classic studies" (e.g., those of Robinson, Baughn, and
Passchier-Vermeer) are on comparable populations. In addition, some of the data are derived
from populations for which noise exposure histories are sketchy, if not absent (e.g., the 1960-
62 U.S. Public Heilth Survey data).
2. There are major questions regarding the comparability of the audiometric tech-
niques used in the various surveys.
3. There are a great number of unanswered questions and areas of uncertainty with
regard to the relationship of hearing thresholds to individual physiological and metabolic
state. The role of the adequacy of the blood supply to the ear (and the possible influence of
changes in that blood ·supply resulting fro.m carqio-vascular respiratory disease or the process
of aging), as well liS the fundamentals of cellular physiology involved in adverse effects with~
in the organ of Corti, simply cannot be stated with any degree of reliability at this time. · · ·
There is some evidence that these non~noise related influences. may be of major signifi~c·e ..
Moreover, part of. the adverse effect of noise on hearing may .l;>e attributable .indirectly to
these influences •.. '·· ...... , . , . ,_, .,·
·.·;.-..
4. There are no iarge~cale lortgitudinai shtdies:on heaiihg loss fu. selected and: are::,·:
fully followed populations, .whose physical state and noise exposure has also been carefully
detailed.
:.·,
Accuracy of Estimated Effects
· .. • , ..
There' is.imperfect agreement' among ~arious. studies as to the exact relationship between . .
sound ex:postire lever. and· noiSe~induced heating loss;. The range of error invoived is on the order
of 5 dBC-2 when examining the difference between the values in any single-study and the ...
values presented in Ta~le C-1. Furthennore, the intermittency correction of5 dB is only an ..
approximation. It has been proposed that a correction as high as 15 dB could be used in some
cases. Thus, the·true·intermittency cor.rection.for.a particular noise exposure situation could.·
be from 0-:15 dB. ·. . . . ' · .. :. ·· · ..
The selection of alternative .population percentiles to be_ protected would cause r~latively
. · small changes. For instance, -there is only a. 7 dB difference in .. protecti.tig the_ SOth percentile ·.·
against incurring.a 5 dB hearing loss instead of the 96th-percentile.
· .• !'• ....... _. ,:
Using. the· assUmption that the noise is of broadband character can lead to errors:.Q.f -5-to ...
10 dB by which .the.risk of the sound exposure is underestimated. This could lead to greater
possible errors if a stibstantial portion ofthe exposure is to r10ise with intense pure tone com-
ponents. These conditions, however, ·ai:e tire in the enviro.nmental situation . . ·.
C-15
.. ;··· .:
~:-
. ·.
.· .....
._.·:._.,· ...
There are apt to be errors in extrapolating beyond ~e 90th percentile in order to pre-
dict effects at higher percentiles".-Likewise; _there ~t be egorS-1n extrapolatiri-g,from known
... exposure data at 90 md· 80· dB :to estimated· effects"aff:r dB f~r a.n 8;IiQ~·~xposur~ to con~
tinuous noise. · .... · .. · . · '· · . · · . · -· · . . :, :. . .': . ~:: .. . ·•
. . _ One fmal ~ote~~al soun;e ·of drror'milerentJrt;ti~~-th~::~6~upatio~~-datajs't~e ;eedto -·.
. compare a population that h~ received:~: occupational·n~~~.:e:xposuie':to:a;populatio~-that .•.
has not received an ·occupational-noise· exp-OSure. ·However-,'this latter:population inay have-·.·.
been exposed to levels of environmental noise ( Qther,than-occupational). As a;cons~quen~,,_in ' · .
... · : _ cOriipUingthe-two grou~s. ~ccupation~d:ex}?~s~~-may'~ei:Y::weU show ne~llgibl~ ~ffects ·.· ...
. ·.. . . ·. · .· below a certain: level because. other enviit:inn:ientai no1ses-ptedominate .. The· direction of the -·
· · · ·.· ·possible error is not unequivocally ciear:;:;lS--certairl·iy. the.advers~ 'effe~idt~Y.~ind~~L · ·---··-
e~posures may very well have l>tlen due: to.~-unfot:;tw.tate ~111Pinatiort.with I10I1":9.<:cupational _.
· · expostir~~~-At this tiirie, it is uniiossibie·tcr.ptoperly analyze the i:>(;ssible bw:that the non~· ··· ...
·:·'-·-··.
occupational noise exposureirtti'oduces~intri the.dataQfTable:c~1: At. p~sentit is' assumed
· to be ne~ble. This. assumptioll will reqUire ultimate verifii:atio:ii by experiinentally relating
·the annual exposure dose of individtiais to their b,ea:ring leve}; Only such· studies Will show .
·how much of what we now tend: to eontribut~ to the·phySiologicl:ll aging proeess ~f the: hear-
ing mechanism could be reduced by "fUrther ~edUclng·wJiat we Consid,e]; to&ly ~.··riormal" .
or "quiet'; environmental noise levels associated ~hpresertt~y livit-lg in.oui society. . . . . .. ,· .· ..
.. ·.:.·":·:·.
Quiet Requirements
-:·. .... ;;/· .....
It has been· shown that the q,Uiet intervals betW.e_en high intensity n.Oise.,butsts· mu~t be
below 60 dB SPL for-the octave· band; centered at 40Q() 1'4 ifre:c4~ery fra·m #l'iri}Wkry thres-
hold shift at 4oooHz is to be fudePendet:tt ot'the"reStfugSound pressure le~~l.C-20•-In this ··
document, sound. pressUre levelofS.Q d.B-.in~:th,e 4000:Iiz. octaYe·b~d js suggested-as a· goal,. _ .
for ••effective quiet""; For typical spectr~ ci comlriunity noise; so :dB SPL in the4000 Hz,
octave band translates to an A-weighted sound level of apP-roximately 66 dB~ Thus, for-: .
·. purposes of hearing conservation, the noiSe level where an individual sleepS. ·should.-ll<l.t be · ·
.. ·. above an Leq of 60 dB, based on the following consideratiorui:
1. Totai TIS recovery is required to prevent TIS from becoming NIPTS.
2.
period.
For some individuals, an ·8-ho.ur nighttime period is the only available recovery
3. In ordertobe consisttmtwiththeidentified levelo.fLeq(24) =.70,_aA 8~iiour
· exposure of'75 dB would require an exposure of 60 dB or less for-the-remain-ing l 61:\o.urs.
C-16
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It should be noted that this level would be too high to protect against other effects.
(See Appendix D).
Contribution of Outdoor Noise to the Total Exposure in Residential Areas
A person's 24-hour exposure to outdoor noise will typically include both outdoor and
indoor exposures. Since .a building reduces the level of most intruding outdoor environmental
noises by 15 dB or more (windows partially open), an outdoor Leq will not adequately pre-
dict hearing effects, because the corresponding NIPTS estimates will be too high. Consider a
situation where the average sound level is 70 dB outdoors and 55 dB indoors. The effective
noise exposures for some of the possible exposure situations are:
. 24-hour Leq in dB (assuming the noise is generated outdoors)
. Indoor Time
(55 dB)
24 hrs
23
22
21
20
16
8
·. ,::
._ .... _ ..
. . , . -~· ··.
Outdoor Time
(70 dB)
Ohrs
2.
3 :···,
4
8 ..
16
.· .. ··
• .. -.·.::,.
24
•.. ·-
Combined Indoor
and Outdoor
-.. >·.· •'
-·-.. ·.···'
55.0
58.6
60.5
61.8 ...
62~9
65.5
. 68.3
·--~··_:·· . ;, .. ·
. . 70 ..
. . -.~-....
Outdoo.r Only.
56.2
59.2
61.0
·62.2
65.2
~8.2._ ... ··
70
'·.-.• ..
The 24-hour value of the combined Leq is essentially unchanged from the outdoor value ·
(less than. one dB) by the indoor noise exposure, so long as the outdoor exposure exceeds
.. _3 hours. Thus, as long as the criterionis.e.stablished with respect to outdoor noise exposure
exceeding 3 hours per day, the contribution of the indoor level of intruding outdoor noise
may be neglected ii1 computing the 24 hour Leq. ThiS conclusion does not depend greatly.
on the actual noise attenuation.proVided by-the house so long as the attenuation is greater·
than 10 dB. . . .
. ,·
.. ··.
C-17
....... : .. · ......
.-: .'
'·-:· ..
'· .. . . ·.·. ~-
Rela~on of. Ldn. to· Leq;~ ~~siden~.~ . . : . . .... :· ·· ... ·_-.:·.-..... • ...
. ::·~ ....
~ ":"i ;. ': •. ·, :~···-~ ·-~·-.).;·.···
Although in residential areas, or in·~eas wheteindividu~IS'~yb~ expeCted to be present.
for prolonged periods or time, u.:would.appear desirable for-practicaL~iisicier#tionsoto use:onlY.L •.
one measure of noise, such a5· Ldn~'it.may --~-rniSleadirigtodo:sO:~ ·tJie·dfffieult~ arises· from. · ·_.
the factthatto relate hearing loss to noise exposure, the basic element to co~-sideds fue.act~l··
energy (not weighted) entering the· ear during a twenty..four hour··period., ·l,eq me~ures the .
·actual energy entering the ear whereas•Ldn:inclu.d~ a .XP.9-l3.Weighting for._tije•;n,ighttinteperio(:t
. Thus, Ldn values corresponding to actu~. Leq valu~. are dep_e.n.d~t up_()n ·the djstrib-ution·Ui· . · ..
noise levels occurring during the total twenty·four hqur. period and could -be. misleading. For .... · .
. . example, the Ldn v.alues corresponding-to Leq(8) ·are·b~twe~·O .. to 6 (iB'~eat~r than the Le~
values~ The lower value corresponds-to -a .situation wher:ethe ayer'clge S()-9-rid·'leveldt.liing the
· · niiht is 10 dB lower than that occuriing·.d~g the.'.Clay.,-whereas: the hlgher:value· correspqnds · .
to the situation when the average so lind level du'rlng the rught equals that·oc~Wrlng during the
day. In residential areas, the difference iit Leq values. for the daytinie and nighttime _period. -· _
often is approximately 4 dB based a~ ca.Iiiinunity. noire meas'rirements~~~zg··lr{tliis particular·"· ...
case, this difference in Leq valuesleads.~oan Ld.n val~e w~is-three·decibelS,above the Leq
value fot the. daytime period. ·· ·' · · ·
. ' . '. . . . . . . :. . . ' . . '.. . . . . ' . ·.•· _·. : .. '. ::~ _: ·•· .· .. ~ •.· . . . . . .. ··· .. ;. ··. . :-: :,_. ... ·~ ..
.... ;_.;·':""·'.
·;; ·:·-.
·. :-.::;.··:.
..:·: ·.·.·, ..
''··· ... ··.·· ... ···r· ·-. ··'·.·
. . ~ ... · ..
..... ··.• ... . ·.· .... :·. ··:.
: .... · .. ' ..
C·18
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C-2.
C-4 ..
C-5.
C-7 ..
C-8.
REFERENCES FOR APPENDIX C
French, N.R. and Steinberg, J.C., "Factors Governing the Intelligibility of Speech
Sounds~" Journal of Acoustical Society of America, 19:90-119, 1947.
Johnson, D.L., ''Prediction of NIPTS Due to Continuous Noise Exposure," EPA-
550/9-73-001-B or AMRL-TR-73-91, July 1973;
. . . . ·. . ...
Kryter, K.D., Ward, W.D.,Miller, J.D. and Eldredge, D.H., "Hazardous Exposure· . .
to Intermittent and Steady-State Noise," Journal of Acoustical Society of
America, 39:451-464,1966.
NationalCenter for Health Statistics, Hearing Levels of Adults by Age and Sex,
tJnited States, 196(}.1972. Vitalimd Health Statistici, PHS Pub; No. 1000-Seties .':. · ··
1 l-No. ll. Public Health Service., Washington, D.C., U.S. Government Printing
:Office~~ ·OCto bet 1965.
Robinson, D .. W., "The Relationship Between Hearing Loss and Noise Exposure,"
Aero Report Ae 32; National Physical Laboratory, England, 1968.
. .
National Center for He.alth Statistics, Hearing Levels of Children by Age. and Sex.
Vital and Health Statistics. PHS Pub. No. 1000 Series 11-No. 102. Public Health
Service~ Washington,D-.e, February 1970. ·
. Guignard, 'n~., "A Basis for Limiting Noise Exposure f~r Hearirig Conservation,"
EPA.550/9''-73-001-Aor AMRLTR-73·90, July 1973.
· Passchier-Vermeer; W., "Hearlng·LossDue to Steady-Stafe Bro~dbmd· Noise,"
. Rep<;>rtNo, 35, Institute for rublic Health Engineering, The Netherlands, 1968 . ··-. ··. ·-·· .. · .·-· . . .. ,_-. . .· . .
-...... .. ·. -· -:-· .. • ·•·•·. · .. ·>
Baughn,W.L., "Relation. Between Dally Noise·Exposure and Hearing Lo.ss as
·.Based on the Evaluationof.6835 IndustrialNoise Exposure Cases," in publication
... ·as.AMRL.:.TR~73~53, Wright·Patterson.Air Force Base,phio . .... · .... . ,.:·~ ..... ...
C-10. . _ Eldred,K.M., "Commuruty Noise," EPA NTID 300.3, December 1971.
.····· . -··.
C-19
: ... ··.-
C-11.
: · .. t····· .· . . . · ... ·... .; .. : ~ . .
"Oecupational Exposure to Noise, Criteria fora Recommended ~tap.dard;Hu~s.
Department of Health, Education and Welfare; Natiomtl Institute. f~r Occupatiqnal
Safety and Health, 1:972 .. · '·· · : .·:;;,<· · . . -. '
: · . .'. ..
I • ~-. ...... ' . ' ....... ~-.. .
. c~ 1:2. . . ... _-f.Vt7kif.8.,,Etf:c;~>~{!j_~~~~~~-jlfa~~~-~~~;fMg"~j~'-~ew·,~~;;~~"JO·:···· ·
C-13.
c.;r4.
C-I-5.
G·16.
C-17.
, ...... ·•· -....
GUideline for. Noise Exposure Con.trol, S6Uizd:a1id· V{biitltlbn; .y:bh 4,:·pp/2 1~24; ...
· November 1970. . . . . . . ••:·• . ·· · ... ·· ·'.·,-::· ~:.:.·. :·. :,• ·.:: : ....... ··
··· .. ,. ·.·.'i··
Watd; w;o~, "On the Trad:i.ng;Relation .Bet\Veen Time and IrtterisitY forlhtermi~ri-t ...
Noise Exposures," pres~mted· a( 86th Meeting O,f A,coustical.Society; of America;
Oct~ber 1973. . · · · · .. •.;: . .. ·· ;.;·,.... · >.::;_:''':: ·:.:·: /' . · ...
Johansson, B~. Ky~ •. B., ~~ .ReopstoHi,:s~.; ·~E:~~-~~tion 6~ i11~· .. H~ug.Dam~ge .·.
Risk from -Intermittent Noise Accordiilg to' the· ISO Reconinl.endations," Proceed.;·
ings of the_1ntematio.nal Congreis o[NoiS.e t:fs•a PublicHea/thProblem; Dubrovrtik, -.
YugosiaVia,EPA 550/9.-73-008, May 1973,: · · · . · ·
. . . --~ .. --~ ~: .•.. _ ... _. * 4 •• :·
·-·.::: .. · . ··-~ .. ;-'" ..... ··· .... ,, . . .
Carder,,,H.M. and Miller)J;),, ~:Femporacy,.T,hx:~$9ld Shifts:·fr.qlll-Prol.onged
Exposure to Noise," joW.niziq[Speech aiz4_Qear~ R.esearc!:J,,l3:603.fl23, I 972.
• • ; •• • • • • •• ,. ··:-.: • ..:·. ' -.. ~ •• _·..... • • • ~--. • •••• • ·-·: w • • • • • • • •
Mills, J.H. and Talo, S.A., "Temporary Jb.eshold.Shifts Prod~<:ed by Exposure to
Noise," Journal of Speech and'Hearing:Research, 15:624-63'1, 1972.
; .· :'· ~
C-18. · Melnick, W., ''Investigation o{H:uman T(;lznporacy Threshold .ShgtCI"TSJ:fr~m ..
. NOise Exposure of·l6 Ho~s. Dmation;'":paper:presented .at'Meeting·:of'Aooustical ·
Society· of America,. 197i · · . . . ... · • · · . . -. . . . · · .. , · ·
.· .. , ... ·. . . .. .. 'C:~ 19. · · · · · \v~d, w.o.:, "The· c~~~pt ~F:Etrecti~~ Qu'iet~-.~. ~~~~e~ted ::anhe astii.Meeung ·;;f
·the Acousti~ So.ciety of Americai April }97~; . . ' . •· . • •. .· · ·
'·.' C~20. ·.· '·'Impact Char~cterization ofNoise Includiitg.bnpllcatlons of Ide~tifying and
Achieving Levels of Cumulative Noise ·Exposure," Envifonmentai Protection
Agency, NTID 73.4, July 27, 1973.
,: ·.
C-20
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AppendixD
. NOISE INTERFERENCE WITHHUMAN ACTIVITIES AND RESULTING
OVER.c\LL ANNOYANCE/HEALTH EFFECTS
·-.. . ... ; .. ~ -. : . . . _·' ·:·· ~
: ... : ~. · .. ·
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App•~ndix D
NOISE INTERFERENCE WITH HUMAN ACTIVITIES AND RESULTING
OVERALL ANNOYANCE/HEALTH EFFECTS
Environmental noise may interfere with a broad range of human activities in a way
which degrades public health and welfare. Such activities include:
1. Speech Communication in Conversation and Teaching.
2. Telephone Communication.
3. · listening to TV and Radio Broadcasts.
4. · Listening, to Music;
... ·· ... 5., . Concentration 'During Mental Activities .
.. , . 6. Relaxation. ,
.. _7.. Sleep. ... ~ ... '
··::····; ;· .. ~ . '. ·,.··
. '·. Interference.·witM1steningsitUations·{items'l.;.4)cat{be directly quantified in .. teinis.bf ·
· · the.abso.lute level ~f the environmental n~lseand:.its characteristiCs; The amount of inter-.
ference in non:-iistening situations {e;g.;) is often dependent upon factors other than the
phYsical chara~tenstics of the noise. These may include attitude towards the source of an
identifiable noise; familiarity with the noise, characteristics of the exposed individual, and
the intrusiveness of the noise ..
The combination-ofthe various interference effects results in an overall degradation of
total well~being .. Maximum noise levels .that do not affect· human well-be:ihg must be de-
rived from-the body of information on human behavio-ral response to various noise en-·
vironrnents.
·.·-.
SPEECHINTE~CE
-.... _
Speech cofunninication.ha5longbeenrecognized as-an ·important requirement of any
···human society; ··It is one of the chief distinctions between humans and other species. Inter-
ference with. speech communication-disturbs normal domestic or educational activities,
creates an undesirable living environment, and· can .sometimes be a source of extreme an-
noyance. <:ontinued·long:-term annoyance is consiciered to affect individual as well as pub-
lic health and welfare in a variety of ways.
Noise can disturb speech. communication in situations encountered at work, in vehicles,
at home, and in other settings; Of. chief concern for the purposes of this report, is the effect
.. _ ... :
D-1--"t/
,· -~ '
. .·_,
• ~ . ~ -= '. .
' ......
.. ·:·
';•" ... ··.:··.:
of noise on face-to-face conversation in4oors ar.td o~tdoors,.telephone use; and radio or tele-•
viSion enjoyment · · .. ' · · · ···•·· .· ' ._ . · · '
···;., .... : . .-.·. .-.. ·· ...
The extent to which enviromnental no~e affects speech co~nntnibatiori depends on .
·· · t1W location .(whether indoors. or outdoOrS); the. ailiountof.noise attenuation provided• by ·
the exterior walls when indoors (including windows and doors); and 1:he vocal effort of the·
talkers .. Certainly; iHs possible to maintain .Communicati_on in th~ face.ofin-trudill:g. noise
if the voice level is raiSed, but m an id~al en~iro,nment;· on~ .should not have to. increase· the·
voice level above that which is comfortable in ord~~-to: ~Iilmuiucate -~y.~. :. ' . . .
. ' .. ·'. . . . . . . . . · .. · .. · ·.~. . • :• .. . ·, -; ·.... . • ..... · . . . . .. . :. ; .· :· :· : ··< . .
·'· .. ,.: ..
Research since the late 1920's hrur made great progress in quantitatively ·characterizing
the effects of noise on speech perception, Areview:of thatwotk is contained· in references
O-land D-4. and it is summarized here as. the basis .for the maximum environmental noise ..
·. levels compatible with pUblic health and' welfare identified in ~ectlon 4. of this report .
. . ...
The chief effect of intruding noise on speech is to mask the speech sounds and thus
·.·reduce intelligibility. The important contributants to· intelligibility in speech sounds cover
a range in frequency from about 200 to 6000Hz; and at each frequency .a dynaniic I.evel
range of about 30 dB .. The intelligibility of speech· will be nearly perfect: if:all these con-
tributions are available· to a listener for his understanding .. To. the extent that' inti:uding
noise masks out or covers some of these contributions, the intelligibility deteriorates more
rapidly the higher the noise level, particularly if the noise frequencies ooinCide with the
important speech frequencies.
~~-'. . . .. .· ·;:-.. :.: .: .• · .
. If is no accide~t, from an evolutionarY point of view, that the hearing -of humans is
most sensitive in the frequency range· inost uriportant for the unci.erstandmg of spe~h;
Therefore, it is not mere coincidence thattheA-weighting,designed to·reflectthe frequency
• sensitivity of the human ear, ~ould also be useful a5 a measure of .the· speech ;interference '
potential of intruding noise. A-weighting gives greatest weight to those CQr11ponents.,of ·.
the noise that lie in the frequency range· where most ofthe speech informa:pon reSides, and,.
·thus, yields higher readings (A-weighted levels) for noises in most of the 200'to6000 Hz
range than .does the overall sound pressure level. A-weighted sound levels will be used
throughout this appendix unless otherwise noted.
The principal results of relevant speech research can be utilized for practical applica-
tion to provide the.le¥els of noise ·that will. produce varying degrees of masking as a function
of average noise level and the distance between talkers and listeners. Other factors such as
· the talker's enunciation, the familiarity of the listener with the talker's language; the lis~
tener's motivation and, of course, the norniality of the listener's hearing also influence
·intelligibility. This value is consistent with the upper end of the range .of levels of sttady
state sound recommended by prior authors in Table D-10 (to be discussed later) as
D-2
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"acceptable" for design purposes for homes, hotels, motels, small offices, and similar spaces
where speech communication is an expected and important human activity.
Indoor Speech Interference Due to Steady Noise
The effects of masking normally-voiced speech indoors are summarized in Figure D-1,
which assumes the existence of a reverberant field in the room. This reverberant field is the
result of reflections from the walls and other boundaries of the room. These reflections en-
hance speech sounds so that the decrease of speech level with distance found outdoors oc-
curs only for spaces close to the talker indoors. At distances greater than 1.1 meters from
the talker, .the level of the. speech is. more or less const.ant throughout the room. The dis-
tance from the talker at which the level-of the speech decreases to a constant level in the
reverberant pax:t of.the .. room is a function of the acoustic absorption in the room .. The . . ....
greater the absorption, the gre~terthe distance over which the speech will decrease and the
lower. the level in the reverberant field .for a given vocal effort. The absorption in a home . . . . . . . . '
w u = ... . ,_ . z: ...
V1 _,_
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;.· .. · ...
.;·.::: .. · .. ·.·.· ..
· ......
····:·.
~-A-wEIG!fl'EO OOON!l LEVEt. IN dB (r~ .20 micmpascals)
· Nm!: -~~ 300 sabinS absorptiOn. ~kal ~f living r.x.ms
and ·beclroats and. is valid for distarx:es ·greater than
cme reter• •.. ··
·:.' :·
FigureD-!. Normal Voice Sentence lntelligihilityas a Function of the Steady
-Background Sourid Level in an Indoor SittiationD-1, n-2, & o-r ·
D-3
....... ·.·
-· -·
.·.::
•··' ..
will vary with the type and amountoHurnishings, carpets,, drapes and other absorbent. •;; . • .·.·
materials. It is generally least in·bathrooms"3.ndkitchens and greatest il1livingrooms,witl'1 ·
typical values.-ranging beM>~en_ ~-SO ~~-;~~0-sabins, .A typicalVal\le.foi:liVih~:_raori1s:and-_ ·'
bedrooms is 300 sabins. For this value of absorption; the. distance to the ·reverberant field· · .. , ..
· from the talker is slightly greater .than.one meter; as: stated above. .. · · ··' :,: .. · ~-. ·. .
:·:.·.
As shown~ in· Figure D~ 1; the· maximum so'tirid levelthat will pennit relaxed oonversa~ ., =
· .· tion with 1 00% sentence intelligibility throughout the room (talker-listener· separation
·greater-than approximately 1.1 meter')is45· dB .. ·
( · .. · .
........ ":_
Ou-tdoor Speech Interference: Due· t6· Steady No~ · · · ·· · · ···.'._:.:·· ....
--.. :-.; .. ·. ···.' ...
· The sound level.of 'spe~h outdoors generallY ·conti]lues to decrease with increasing ·
distatice between talker ·and listener:with the absence of reflecting-wall~ which provide the .
. reverberance found indoors. Figure.o,;z.pieserits,the diStances between talker and listener
·for satisfactory outdoor conversations, iri different-steady background noiselevels(A,;
. weighted), for three degrees of vocal effort. This presentation· depends on·thefact that
the voice level at the listener's ear. (outdoors) decreases :at a predictable rate as the distance
between talker and listener is increased. In a steady background noise there comes a point,.
as the talker and listener increase their separation,where the decreasil1g speech signal is
masked by the noise. ·X•
·The levels for normal and raised-voice .. satisfactory conversation" plotted in; the fig-·
ure do not permit perfect sentence intelligibility at the indicated distances;.'insteatf,. the
sentence intelligibility at each distance is 95 percent, meaning that 95 percent of the key
· · words in a group of sentences would be coirectly·wule~tood. Ninety-fivep.ercerit sentence ····
intelligibility usually permits reliable. communication because· of the redunoancy in nolTilal .
conversation~ That is. innormal conversation; some unheard·words can bednferredjfthey
.... •'.•' .
.. :occur in particular:, familiar ¢ontexts. Moreover, the vocabulary· is often-restricted,. whlf.i:h ~. ·>····
alsO' helps understanding. Therefore, 95 percent intelligibility is satisfactory for most situ-'
ations.
The levels given in Figure D-2 for relaxed conversation permit 100% speech intelligi-
bility when communicating in a normal v:oice. This situation represents an ideal environ-.
ment for speech communication and is considered necessary for acceptable conversation in
the indoor environment. However, it does not defme the situation outdoors where 95% ·
intelligibility is adequate, and communication outdoors generally takes place between
people who are walking oi: standing relatively close together, about 1 or 2 meters. More-
over, these levels appear to be consistent with theneed for speech priva(;y.
D-4
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~
......... Of
~: s. t'.
..... ~, ~ ~.. ~ n ,~ ~,.
.......... <'to -sdtr. '~ 1~ ~&r ";~~ ·.
"~c ~4~N ~ ~· .. , ·~~ ~.,. ,_., c~ (_~ I I~ '>• . . ~..,,.., -f--1~~~ ~"';~·~;:· ' ~ l'. . ~ .· .,,0·~-~-~ I I ~~ ~ .. ~ l K-9p, . -.. ~ r:--f-' . --. f,----, -~~ ~~. i ~"' '6 ... . . ,, .
N: l ' +-· --f'S~ .......
~
80
70
60
. ·.·-..
.. I ~ ..............
0 .........
··2 .3 .4 ... 6 .. 8 I ·1.5 2. 3 -'·•·· ·1>· S·lO 15 20
. _._ .·~ :. ··.:_. ~~cotrf'9'. Olttance~ tn-Met~
•.-·:, .. -.. : ·: -.:-~. --:' ... ~ .·. :. --. ... ::.
Figure 0~2. Maximum D~tances Outdciors Over Which Conversation is Considered
to be Satisfactorily· Intelligiblejn. Steady Noise. o-1, D-z
. . . .
._·:·; -·· .
. . . . .
The data for 1lorinal and raised voice ·,~f Figure D~i are tabhlated. for ~-o~vecie~~e
below: . . .·
·.-· · · · ., Table D-1 ·· ' ....... -··.
.. ·.··:·
STEADY A-WEIGHTED NOISE LEVELS THAT ALLOW COMMUNICATION
. wrrH 95 PERCENT SENTENCE INTELliGIBILITY OVER VARIOUS .
DISTANCES OuTI:?OORS FOR DIFFERENT VOICE LEVELS o-i .
-~ ~. ,-. -' ... : ..... -~. ; · .... . , .. -.-····.:.
. ,.,--•' .. ·.-. ':-
VO~CE LEVEL .. : . . _.--. .;,.:·--:: ::· COMMUNICATIONPISTANCE.{meters). . ·
•(•-: .. :;·:··:·.-.··· ·. ·. ····:·: ..... ·.-: .. •.::'•.: ..
-· 0;5 : 1 :~2. .. '3 .4 . ·::··1 -..
. ··::· ··,···
Normal Voice (d~) 72' 66 60· .. 56 54
Raised Voice (dB) .. -78. 72 ·' 66 62 60
D-5
5
52
58
.. :··: ..... ·.
.....
.. ·.•; ..
:;·,,
··.: .. ·.:· ..
·,,: ....
. If the noise levels. in Figure D-2 and Table D-1 are exceeded, the speaker and listener must
either move closer -together or __ expec:t rf\4uced intelligibility;For-example; conSider a con~
versation at a· distance of 3 met en in· a steady backgr9uri4 n,ol!le .of 56 d]j;"using' not.malvoice
levels .. If this back wound level is increased from 56. to 66 dB~ ·ilie speak.~;JrcS \\lilt either need '
to move from 3 to .1_ meter sepimition to;~aintain t!u;.·.same iil:telligibiDty;·or artertta•tiyely; .
to raise their voices well· above the r.Used-yoice effort. If they ·remain 3 meters apart' with~ ·
· ·• · out .raising. their voices, the intelligibility. wo~ld .drop~ frmn 9-5 to 6s p~rcent .
. . :. . ' ' . . . . ' ; ' .. .··. . .. ·. ~ . . .·:. ·. ' ,·.. . . .. . : .-·. . ... , .. . . . . {.. ".. -. . . :. ~ . . . : · ..
. .
., · · · •. Speech Interference in the Presence ·of-F}uct:Uartng .Sound Levels .·.·.,,. ·.::.· ........ ,· .: .. ·· :'
'·-· .... ·
........ ·.' ......
. . :The data in Figures D-'1 and ~-2·ate based on te~tSJnvolvirig.steady, contiriuous.~ou:rid.
:·· .. It might be questiO:ned.whether:these results would apply to souhds which have fluctuating
imrels~ ·For example, when intermittent·~o~e intrusions,·suchas those from aircrafH1yovers
"or truck passbys, ru:e Superimp.osed on ~.steady noise background, the equiYalent sound
lfivel is greater thanfu~ level of the background a}qne. lf:tlie s.o~-nd levels of Figure D'-1
and D-2 are interpreted _as equivaient round levels, it-bowd be argued ·that these values
could be slightly increased (by· an amount depending on the st~tiStics;ofthe no!Se); be"
cause most of the tiffie the background noise level is actually lower than the equivalent
sourid leveL. · ·· · · · ·· · . · '' ·· · · ·· ··-. . · . .
The amount of this difference has been calculated for the cases of urban noise and
aircraft noise statistics shown irt Figure I?-3, . The data in this. figureD-3 .· inc,lude a wide range
.of urban sites with different noise levels ancl an exaqtple of aircraft nois(; ~til site near a .. :
major.airport. In each ~asethe s~ech int~ll~bilitY·~~ calcclat~d frorri th~.sJandard sen-..
. ... .. ten~e iiltelligibility (:U1'Ve04 for Y.ariO-US;Y.alUeS ofLeq,.fttst With steady noise·and then with.·
the twb'~specificflucfuating hoises of Figure D-3. The calculation consisted-ofdetermining.
' .. the incremental contribution to sentence "intelligibllityfor eacli level (at approxiiri.ately .
. . ... 2 dB increments):and-its :associated percentage o£ time occurrence• The incremental con-; :.:
tri:butioris were then-summed to obtain the total value of intelligibility m:~ch case;
. '···:·The results,. shown in Til.bie D-2 ~ demonstrate that, for 95 percent se11tence intelligi-
bility, normal vocal effort, and 2 meter separation between talker and listener outdoors,
the maximum Leq value associated with continuous noise is less than the maximum value
for an environmental noise whose magnitude varieswith time. It is therefore concluded
that almost all time-varying environmental noises with the same Leq would lead, averaged
over long time. periOO,s, to better intelligibility than the intelligibility for the same Leq
values of continuous noise. · ·
Alternatively, for a fixed Leq value, the percentage of interkrence with speech ( cif'-
fmed as 100 minus the percentage sentence intelligibility) is greater for steady noise than
D-6
---··
: ····<·
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30
20
' 10 Range of Urban Noise .Samples-~ ~
0
from Community Noise Study -....... ~ ~
(Excluding Aircraft Noise)
~ ~ a .., 4 dB
" ~ ~ ~ §§ ~ ~ ~-I
"' -10 -o
!: "' "'<.:: ::22 ~ ~ ~ 1~-L ~ ", ~I'
<T .. .....
-20
·x ..... ' Example af Aircraft Noise_ ...,;_
~ :--..... Near. Major, Airport
r----30
-40
1 2 s 10 20 30 40 50 60 70 so 90 95 98 99 .
·Percent· of. Time· .L x Value· wllf .. be Exceeded
Figure D-3. Cumulative Distribution of Typical Community Noises During the
Daytime Relative to the Equivalent Sound Level,D·39
·Table D-2
MAXIMUM EQUIVALENT SOUND LEVELS THAT ALLOW 95 PERCENT
SENTENCE INTELLIGIBILITY AT ADlSTANCEiOF 2 METERS
. USING NORMAL VOICE EFFORT OUTDOORS
(From Figures D-2 and D-3):.
: . Noise Type Leq in decibels
.. Steady · 60
·. Urban,' Community ~oise
,: . -~ . .. . . .
60+
·Aiferaft. Noise
._-_ .. ... 65
.. -·::
D-7
·., ... ;
. ·.··
. •.;:-..
· .... _
for almost all types. of environmental noisewhose magnitude varies with time .. The relation-
ship betw.een Ldn·andthe maximump~centage .s~t;~.ten.c:.e Uiterferen~e (Le.,.forcontinuous
noise) is given in Figure D-4. · . ··· · .. _: .. · ' '· : · ·-. ,. . .. · · .. ~:. ';·;. . .':
100
~-80
1:1 ... . f:5'::.
~ 60 ... u z-
= z .... .,.. ...
~ .... ·z
.... ·;···· · .. :·: .. ·
•". G
. ,; .
. ~·· · ..
. ·.·:··-: .. -_.;.-.-· ··. ·:
·., .. : .. :·:·-·.,.;:,; ....
·. ~. ... . ' .• ..
··:·:."·
.. ·. . ··~~· , .. '.:·, ·.-.-
· .. : .. ·;_,·.,
. . -~ .... ~-: .
. ··.· .
··: • ...
.... :. ~ ··-:·· ; ..
OUTDOORS·· ....
· (NORMAL ...• ·
VOICE·· .
LE\tEt AND
:2 METERS ·
SEPARATION)
,.: ......
... u ·:·; .. ··· ·· . .-·::.
"' ~ : .. -~-.. ·:·;····-··· . ·: . ·.:·· •, : . ::~'· :;-
OUTDOOR DAY NI~HT AVERAGE SOUND LeVEL, Ldn' IN DECIBEl.s
( re 20 Jlicropascals)
NOT&: .. Percentage·_ interference .. equal·s· miriu·s· percen.t~9 e .....
intel:l.i~bi~~ty!. and LdR is. ba""" . ., Ld + 3'. ~3 ·· .. · . . .· ·-., ., .
Figure D-4; Maximum Percentage Interference with. SentenC-e$
·.<. 8s. a Func.tiori ofthe Day-Night Average Noise Levei. ·. ··. . . .. .
·:. r< .. : .·: . .,. ··~·
The .extreme example of a fluctuating noise is.a·series . .-Of.Jfuise· pulses:of constant level
that are of sufficient magnitude relative to the background to control-the· equivalent sound
level. For example, there could• be a cas~ where the background noise dUring the off·cycle
is assumed negligible, so that when the noise pulses are not present, the speech intelligibility
is 100 percent. Table D-3 Shows how the percentage interference with sentence intelligi-
bility varies as a function of the leveland on-time for a cycled steady noise whose level and
duration are always adjusted to yield a f1xed value for the equivalent sound level. Two
situations are envisaged: indoors, relaxed converSation, Leq = 45 dB, leading to 100 per-
cent sentenc~ intelligibility in the steady, continuous noise; and outdoorS, nonrial voice
effort at 2 meters separation, Leq = 60 dB, leading to 95 percent sentence intelligibUHy in
the steady, continuo~s noise.
D-8
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Table D-3
PERCENTAGE INTERFERENCE WITH SENTENCE INTELLIGIBILITY
IN THE PRESENCE OF A STEADY INTRUDING NOISE CYCLED
ON AND OFF PERIODICALLY IN SUCH A WAY ASTO
MAINTAIN CONSTANT EQUIVALENT SOUND
LEVEL, AS A FUNCTION OF THE MAXIMUM
NOISE LEVEL. AND DURA TIOND·39
(Assumes 100%intelligibility during the off-cycle)
A-Weighted ievel
of intruding
. noise during
. . "on-cycle,''
Duration of
intruding
noise as
percent of
Percent
. interfer-
ence if
intrud~g
noise were
Average
percent .
interfer-..
ence in
·· · Situation · ·· · ·. · · ·· ·'· · ·decibels·· ' · total time · ·.· continuous ... :cyCled, noise · <: .. ·
INDOORS
Relaxed con versa~ ·.
tion, background
Leq =45 d~,
1 00% intelligibility
if background noise
were continuou~ ·
at 45 dB
OUTDOORS
Normal. voice at 2
meters, background
Leq = 60 dB, .
95% intelligibility
if background
noise were con-'
· ·· tinuous at 60 dB
45''
50
55
60··
65
70
75
80
60
65
70
75
80
.. •... .. 100
-
32
10
3
1
0.3 .
0.1
0.03 .
100
32 .. ·.
10
3
'l
. D-9
0 0.
0.5 o·.16
1 0.10
2 0.06
·6 . 0.06
40 0~12
100 0.10
100 0.03
5 5.0 .
7.7. 2.s•
53 5.3
100 3.0
100 Lo ..
·::···'.•
•' . .
The combination of level-in the.iirst-column·and,·dur~tionin the serondccolumn are
such as to .maintain. constant L~q}ot ~_acli sittiation;}~.~ 4~-:fu~por~ ai1(:];·60.'dB i:lutdoors.
· The third column gives the, percent interference with .sent~:nce . .intell1gibility that woUld
apply ifthe noise were ste~dy-~nd.99~twus w#h:ih~J~;~(i.Mi~atediizi.~f(>lumRL·. The
fourth. column giv.es. the percetrt;int~f~nce; fot'thei:'CY:~d: ~~~:in each·~~;· · ·
. ·.' .. ·. : . -~··'. •'.:::;:.:i-••, .. · .;.· .. . .·:··.·.<·-~·~::::;;<:~:~:;~;-~.~--~.:~: .. ~~;;:_ .. :\!~.--. •.<,~-.--,~--..... ~;.·.. -.. :·~: ·:.
The results· for·thls extreme case indicate thai·no matter'how eXtrehlethe n<lise fluc-
tuation for the indoor case, on the averag~ there is n.egli~ble speechil1terleren~fo~ Leq =
. 4SdB. On the other hand, with'Leq = 60·d~outdoors~the averagespe~·mt~rference
·_tends to decrease as the fluctuations ofthe noise become more extreme;, :However, it should
be recognized that if the duration of th~ in~ding ·iioiSe .were to:t*e ·place· iil-one: continu-
ous period·, and if it~·.percentageinterference ( coiunin 3} ,w~:-~q~ tb:JOQ-;:tht~.h:it_ would
blot out all communication for tile duration,of!t~''<m7cycle'"~ .· •
. .. .. ~.: _.. ·-~· ..
.. ·.··· :_ .. ·.:· .,.· ... ; ....... ··· ··.:• .. ;.
The following sections .rehitihg ·tO icti~ity ~terferenc~:·~~ya~~. and 6o~mu~ty
reaction utilize eq~valent sounq}~"X~ ~ith:a= night~e, weightmg:(Ld:Ill~ll.ich..i~:discussed
more fully iii Appendix A. Howev:er, f.q~ ~he speech int~ere~ee effeCts .cifnoise,·a·similar
measure without the nighttime weightirt~(Leq> has..~nemplo~d~ _l'O.:~ow co1llparison
between the·various effects stated above;,soirte rela9onships·are nec#5acy'to·anow at least
approximate conversion from Leq to-Ldn· For mdoor levels such as those desCribed in
Appendix A for various lifestyles, levels during the .day are at least 10 dB higher than those
during the night. Thus Leq is virtually the same asLdn for ~normal indoor situations.
-·' ..
For an outdoor Lcfu of 5 S ·dB or ~ss, day time lev.els. (Lei) -are genefully a: dB hlgher
than the.nighttime levels (Ln)· For. this situation;. ~dn is still q•uite close to Leq during the
day~ The-correctj_op. is less than:one dB .•.. For leyels.-~greater than Ldn:?S; Q;B, the-Qighttime
levels are generally only4 dB less than during t~ daytime. Fot:: the~.cas.es;Ldn is3 dB
higher than Leq during the day. . .. · . . . . .. ·. . ' . . ' . . · ·
..... For values of Ldn ·between 55 and 65, further interpolation is nee~ using
Figure A-7. .·. .
ACTIVITY INTERFERENCE
Activity interference due to noise is not new. The· recent EPA doct;1Jl1ent~6.ncerning
. public health and welfare criteria for noise o.;s mentions an ordinance. en~~ted 2500 years
ago by the ancient Greek community of Syharis, banning metul works and U1e kePpin6 of
D-10
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roosters within the city to protect against noise that interfered with speech and might dis-
turb sleep. History contains other examples indicating speech and sleep interference due
to various types of noises, ranging from wagon noise to the noise of blacksmiths.
More recently, surveys have been conducted which further demonstrate that noise does
interfere with various types of activity. For example, Figures D-5 and D-6, based on research
done in England, give activity interference reported by the people who were disturbed by
aircraft noise for various types of activities as a function of the approximate Ldn associated
with noise from aircraft flyover.s D-14 (for explanation of the term Ldn see Appendix A).
Thus, for an outside Ldn of approximately 55 dB, over 50% of the people who were dis-
turbed reported some interference with TV sound, and 45% reported some interference with
conversation. At the samelevel; about 45% reported that noise occasionally woke theriiup,
while 30% claimed,it sometimes,disturbed'their relaxation .. The figures also .indicate: that at
... higher noise levels, .greater percentages of people .who were disturbed have reported activity ....
interference~
"U
~ 60 .2 ...
0
. ;J?. 50 .. 8-
tf KEY
'0 · 40 .1-~+---+-r----::~~!:t---+--+..,.....-..,r--+--1 Startles
· . .:,, .~ ·30. t--+---+~-t---+--+.<1?":-+--:--t---+--2 Keeos From
C: · Gol~g to S.leep
~ 20· 3Wokes Up
·~ 4 Disturbs.Rest
or Relaxation 10 ...._ ...... _ _.__...__~...:...-..J.--..1..---L--'-~_._..;,_...._---J
. 3'0 4 0 50 ' 6 () 7 0 8 0
Approximate Outside Day-Night Equivalent Sound Level (L 0n) in dB
... ·:· ·---,~ ... ·. ·.· ...... ·.:
Figure D-5. Percentage of People Disturbed by Aircraft Noise
for· Various Types of Reasons Concerned With Rest And
. Sleep D-6 ·
Dll
·.··:· .. ··
.:• .. . ' '•• ... ;, . ·,· .... ; : ~ ..
. ··: ;:
1 1 70 ...,__+:.......-t---+--,-+----:,....f-~i>" .... ...
. ... _.., .
·:.::.
O 60 1---+---t---r-~~ F---+--"~_._........,~....._-~.......,.._...··~.-:-·"""i·:· .····.-··.
G ·... ··_:~ -~. 6 £. 50 ....... ----+---+--+---'-+-....... ·/: 5= Inter-feres with
-··"'. : ··. ·TV S(lund· : · . 0 6. Causes TV & 40 1---+--+---~~~ 2 . 5 . · Piet.ure Flickef
· ; . 7 :i HotiS:e Vibrates-; ~ 30 1---t----~--v:.......-t---+.-.;.~1--+-"--+--'-. 8lnterferes with
cf .a
20----------._----~--~--~~~~~~--~~
·jo 40 so 60 j.Q
Approximate Outside Day-Ni gh:t Equiva 1 ent Sound Level
Figure 0-6. Percentage of People Disturbed by Aircraft Noise for
Various Types of Reasons Concerned with Domestic
. Factorsll-6' .:. · ··
,. .. . . . : ''· : ~ . . . ' .
. L~ter research in the USAD-7' provides the fuforniation: on activity. itlielference shown .
· in: Table D-4 .. This table gives the activity disturbance percentages of those who repOrted· .
that they were extremely disturbed by the noise, which accounts in part for-the low per-··.
centage values; It was reported that the daily activities of 9&~6% of those q:1;1estio.ned
(about 4ooo people) were disrupted one at more times by aircraft n6-iSe~· :·More ·activities ·
are ~entioned in Table D-4 than· in the previous tables. FQr example,.telephone use; read::.:
ing, listening to tapes and records, and eating were reported to have beert diSturbed by
noise.
A studr performed in the NetherlandsD-8 gives further evidence thlit .acti~ity; interfer-
ence is associated with noise (see Table '0-5). The data were taken in the urban/suburban
areas in the vicinity of the Amsterdam Airport where the Ld~ ranged from45 to 85 dB ....
Activity interference is shown by percentage of people interviewed who have been fre-
quently or sometimes disrupted in various activities. Also reported are the estim::t.ed
tolertance .ltmits for various portions of the exposed population. Thus, in an area where
D-12
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Table 0-4
PERCENT OF THOSE PEOPLE WHO WERE EXTREMELY DISTURBED
BY AIRCRAFT NOISE*, BY ACTIVITY DIS-TURBEDn-7
_ ~ctivity Percent
TV /Radio reception 20.6
Conversation 14.5
Telephone 13.8
Relaxing outside 12.5
Relaxing inside 10.7
Listening to records/tapes 9.1
._
. ·~leep ' ... 7.7 . -.. ' .... .,
Reading 6.3
..
_ Eating 7; .-··-.. 3~5 _, •·· ..
*Percent scoringA or S on a 1-5 scale.
·.··· .. ,:··:
". noise produces ':j;iredorninantiy moderate.'nuisance,~/the ''toierance limit;~-is reach~d for one-
third of the population. Thirty-one percent report being sometimes disturbedby noise dur-. -.
ing conversation, and 21% report being sometimes disturbed by noise during·sleep; occupa-
tional disturbance was reporte.d by -12% •. (The judgment of "admissibility'~ with respect to
well-being in Table 0.5 istheresult.ofthe.referenced study and not a conclusion of this report.)
--. Arecentstudy.n>9 in the USA found-that 46% of the 1200 respo.ndetits were annoyed
-by surface vehicle-noise at some time. Activities whlch were rep~rted disturbed are. indi-
cated by percentages shown in Table'D-6. Here we see that sleeping is the activity most
disturbed by surface vehicle noise, followedirt order by listening to TV, radio or recordings;
mental activity, such as reading, writing or-thinking; driving; conversing; resting and walking.
From the studies reported hei:e •. itii(cl~ that noiSe does, indeed interfere with various . _ . -
._activities m.our everyday lives. Unfortunately, most of the studies do not provide activity
_interference-as a-function ofnois·e exposure. However; the activity which is most sensitive
to noise in. most of the studies is speech communication (including listening to TV), which
can be directly related to thelevel·of the intruding noise.
D-13
··:.·.
. . .. : _. ·~ .
.. , ... ·
: ~ . . . . ~-. . -' .
.,_·:.·
··-'.:· .. :.::.<· ··,,.·.:.
. . , .. _ :-,::_·--· ·.: ...... · .
':'·
·· .. -.: ...... · ....... -: ..
.. . ··~ . :. ... · .. :c
'' . PERCENTAGE OF ·PERSONS":INTE.RR.oGATEil~::<';:.·,~
WHOFEEL·THATTHEY.HAVE .. FREQtlEN.f:LY;;(F}QR SQMETIM~~~:(s}·:.
· · BEEN DIStuRBED n~: toNVERSA noN,. · . · · · . . .. •
... RADIO lisTENING; 'TELEVISION;·ocq:JPATIONS; SLEEP;\ .. ~·,· ..
FEEL AFRAID, ANO·of. PERSONS IN WHOSE EXPERIENCE• · · ·.···.
. .. . : ON THESE OCCASI9NS THE.HO{JSE yu3RATES';·< ,, ; ... : ·: .. · .
ATMEAN VALUE OF'THE''NUisANCES'COR~S.~···"'·· .. "'<'
.·::·· ..
·';::,,;·.-.'
. .-.. ···-:: .
~ •• ! . :' •• : •
...... -.-.. :. ::. :.~--. ~-.. · . . .. . . . :., ·:~ ....... ,·.: ;: ;._~,'; . : _.:':' -:-. ... :: .;·i~: .. :·::~. ;'·."; ;; .:.' ·' ~-~:-·.: ; . . ..-·. .·.· ·; ~ :
Mean
NWSailce
Disturbance
of
Conversation·.
. Scqre l .F* S*
0 0
1 7 12
2 :16 24
. ·· 3 27 .: 3'1
4 39
.. •.· .
s 56 37'
6 67 31
7 83 l7
..
Disturbance
of Radio
. listening
.F
......
Disturbance · Disturbance
of · · · · · . : of' · · • ·
. Television· · Oc.cupations. : A:.i,iaid, · .... '; .. :.--: i.···-.:~ ••..
·.-.
0 · o .·. O'·,. · ····o :. ''·'· .. ·,·::;;· ..... ·.
2 '4 2$'·.
·, .
s 8 12 · .. ·, l8 3 T' 48
·.•· > ,;. ; . ' : ·. .:; ··~ _-.~ '· : .. ' . .· ' --:;
.............
66
.. ........... ·
10 J.s·· 20' '·'23'''''; 7
18 22. ......
27 30 . 42' . 26 19 '28 ·91
.. ·
38 36 57 26 34 39 .; 94
56 44 72 28 55 45 .· 100
*F denotes "frequently" S denotes "sometimes"
D-14
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Table D-5 (Continued)
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Admissibility from point of view of
[ House Disturbance _physical, mental and social well being,
Vibrates of'S1eep ... Nuisance in regard to which the stress is laid
Felt on disturbance of sleep, disturbance
n YES F s Subjectively of conversation and feeling afraid
c 0 0 0 No nuisance --•.
..
[ 21 3 •.. 7 --~ Slight nuisance Adlnissib le
Slight to Admissible; the tolerance limit is
41 6 14 moderate reached for about one-fifth of the
[ ···nuisance •
.. ····· population~. ...
.... ·Predominantly Limit of admissibility; the tolerance
56 .12 21 moderate limit is reached for about one-third c
E'
[
nuisance .... of the population.
·· .. ·;· .. ; Predominantly · Inadmissible; the tolerance limit. is
72 .... 20 .>28 ··serious . exceeded for about half ofthe · . ·-·.· .. nUisance · population. ... -• .
... ..-Inadmissible; the tolerance limit is·· Serious 83 31 .. 33. ·nuisance exce.eded for about two-thirds of the
oM''O population .. .. --~-.;_ . . .. . . .. . ..... . . ..
.._, __ _
b ..
~
....
92: Intoleiab.1e · AbsC>iutely>.iriadmissible · .. . . ·44 . .'. '42 ..
. --. ... .. . . .. . :--, .... -.· _.· ..... ·. . ...
. . ~-.. ··-· , . .. . •':'• ... ... . ·-· . . · .
· ... ., .. ---:.·--·. . . . .. ···-·· . . .. .. .,:·: ; .... 100 72 _28 Intolerable .. Abs?1ute1y inadmissible . .. ....
[ ; ...
[
· ... _ .... ···· . D-15
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....
.-·: . : ,;•;. ~--· .. '.. :. _;
·:·:c··
· · Table D-6 : ". ·
ACTIVrfiES OF RESPONDENTS DISTURBED BY SURF ACE :VEIDCLE NOISE
(All SitUations: ~espondent's Usual Activity)0.9 ; :;
. . . . . . ' ::I.= . ' .• -~---.
;,, ·-
Category
·-._ . :. ~-· ·, .-.: . .·. :· . ,· _:.: .
Driving
Walking
. . . .
Talking with people present
Wo~king at home •
Reading, Writing, thinking ..
Sleeping
Other
Not relev~nt
... ·· ..
:-·;
Listening to TV, radio, records
Resting (awake) .·
. Not ascertained · ·
·• ·.:-.: .... ··
··-··
. • . . .•' . . ~ . ..... _:_ .. · .
'_< :: : : · :.p~I-ceriiage;
NJ::6r-. ·· <i('l'ot.al
. : .. · -·· : '
· · '·sii~d<lns · Situations ·. . .
. -· ·:: ... -_,; ... ' •: ~
~ ..... ~-....
47
. T6
42-
li
. ...... 80 ..• : .•.
: . · .. 15.5--
. 13-··
_17~
92
35
22 .
-· .. ·
:-::. · .. :·.-.:-···'·
T
2
6.
······2··:
:~·:t:2 ····-.. ·
22 ... ·
,z ..
. ~.2.6 .. : .
13 .. ·
s
. 3
. __ ._;_·
-... ·r.-: ,
... :·
·····-....... .
-:: .·.. .
·:·-.-.'.: ..
. -.. _
. :. :::-. :i'.'._. •-'::'. Total· ·'··· · ..
693
'··'·-··,,::..··
'COMMUNITY REACTION _TO ENVIRONMENTAL NOISE . · ~ .. ·. ,;_,' .
· .. ·:.-t" . .'
. :··'
There are two methods of indirectly assessing: .the cumu}ative effects. of environmental
noise on people. These are examining the reactions of individuals or groups of in.dividuals
to specific intruding noises, either (a) with respect to actions taken (complaints, suits, etc.),
or (b) in terms ofresponses madeto social survey questionnaires. Thefus.tcategory; involv-·
ing overt action· by individuals or groups, is summarized in this section, and key:.data regard-
ing the second category, involvingresponses indicating annoyance, is summarized in the
next section.
• .... _
. -. . .
In the last 25 years, many new types of noise sources have been int~~duced into
subu.:ban and urban residential communities. These sources, such ajet aircraft, urban
D-16
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freeways, new industrial plants, and homeowner equipment, have created numerous com-
munity problems with environmental noise. These problems have provided significant data
· and insight relating to community reaction and annoyan~e and stimulated the development
of several indices for measurement of the magnitude of intruding noises.
Various U.S. Governmental agencies began to investigate the relationships between
aircraft noise.and its effect on people in communities in the early 1950's. This early
research resulted in the proposal of a model by Bolt, Rosenblith and Stevens D-lo for
relating aircraft.noise intrusion. and the probable community reaction. This model, flrst
published by the Air Force, accounted for the following seven factors:
1. Magnitude of the noise with a frequency weighting relating to human response.
2. Duration of the intruding noise.
3. Time of year (windows open or closed}.
4 ... Time ~f day noise occurs •...
· 5. Outdoor noise level in community when the intruding noise is not present.
6. · . History of prior exposure to the noise source and attitude toward its owner
7. E~istence of pure-tone or impulsive character in the noise.
Correction for the-se faCtorswere.hlitialJy niade iri 5 dB intervals since the magnitudes
of many of the corrections were based solely o::t the intuition of the authors, and it was
considered, difficult to assess the response to any greater degree ofaccuracy.D-11-13 This
model was incorporat~d in the flrst Aii Force Land Use Planning GuideD-14 in 1957 and was
later simplified. for ease of applic~tion by ~e Air Force and the Federal Aviation Adminis-
tration. ·• ..
. ': ·-..
Recently the day-night sound level l1aSbeen derived for a series of 55 community
noise problems I>-J to relate the normalized, measured Ldn with the observed community
reaction. The normalization procedure followed the Bolt, Rosenblith and Stevens method
with a few minor modifications~ .Thi:correction factors which were added to the measured
Ldn to obtain the normalized Lan are given in Table-D-7 •. The distribution-. of the cases
among the various noise sources having impact on the community are listed inTable D-8.
. The results are sumniarized in Figure D:-7~
···-··:_:· ... ·. ... -......
. . -' . . . .
The "no reaction''.responstHn·FigUte 0-7 cc>rresponds to a normalized outdoor day-
night sound·-level·which,ranges betW,een 50 ·and 61 ·dB witlJ, a mean of 55: dB .. This -niean
value is. s dB below the-value ·that was utilized for: cat~oiizing.the day-ni~t sound' level
for a "residential tirban community,;' whlch is the ba;ellnecategory for the data in the
figure. Consequently, from these: resUlts;· 1t appears thii.l no community reaction to an
intruding .noise is expected, on,_the. average, when the normalized day-night sound ievel of
an identifiable intr\lding noise.is.approximately 5 dB less than the day-night sound level
D-17
. . . ~ ..
.. :·;. ·'.
Table·I)..?::· ... : ~:; ......
. : . ·•... •· . cORRE¢TIONS TO IiE ADDED •. .
.. ·. ·:·
TO .THE MEASURED DA Y:-NIGIIT'·SOUND, ,LEVEL JLdnk
. . . . .··· OF"INTRUDING.NOISE . . <> . 0. ·· .. :
. ' . : _. ·. TO• OBTAIN NORMALIZED LJn~3 . . .
.··Amount ·.
ofCortectio
.. ·to be Added •
.... · :, ..
.·Type of·
Correction' ·· · · ; ... :.: .. :.::::.Jr%-!e~~~t .. ;:.·: .....
Seasonal
Correction
. . . Correction·
. : .:~ .•· .. ,. ':' .... : .. . for Outdoor.
·· Noise Level.
··:=:.:.. Measuted· in
Absenee·of
· Intruding
Noise
Correction
for Previous
Exposure&·
·Community
Attitudes
! .• :. • • • • • ~ •.
·.•· ... :. <•
··::• . ,,. . .· · ... : .
Pure Tone
or ImpulSe
. Summer (or year,.;round .operation}
Winter only (or windows always closed}··
'. ·. 0 , .
' -5
.·.:·
· ' Quiet subW.ban or rut-ai commwiity · (rerti~te ·. froni larg~-'
. ,. cities and from industrialactivity·.a.rid-tfucking) < ·,>: · .. ,_, '
·Normal suburban eoriummity (notloc<lte(fnear industrial ··· ... +5
activity) . . . .
Urban residential community (riot."immedlatelyadja-cenito:
he~vtly trave.Ied road~ and indtistrial areasY · · "' .
Noisy urban, residentialcomnmrrlty (near i:e~ttvely busy ·.·
roads .or industrial areas) . .. . · · · .. ... ·
Very noisy urban residential community .
No prior experience with· the intruding noise
Community bas had some previous exposure: to intrUding
noise but' little effort is. bemg made to cOntrol the noise;
This correction may alSo be appli~d· in a· situatiOn whete. ·.·.
the community has not been exposed.to·the noise·.·
. previously, but the people are.awa.re. t:hat bona fide effcn:ts . are· being made to ,:C:Ontfolthe noi~ . . . . . .
Coinmunity has had oonsiderable preVious exposure to the ·
0
'L5 -··.····
-10
+5
0
i,ritfuding noiSe and the noise maker~uelat:ions: with:the'-:;::'' .. :· .... :.:p;;·. ' · .. ''.:.;e
comritunitY are good · · · · '
-Community aware that operation causing noise is very
·necessary and it will not continue indef"mitely. This
correction can be applied for an operation of limited
duration and under emergency circumstan-ces.
No pure tone or impulSive character ·
Pure tone or impulSive character present
D-18
. .... . . ~ ..
.....,.10
0
+5
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Table D-8
NUMBER OF COMMUNITY NOISE REACTION CASES
AS A FUNCTION OF
NOISE SOURCE TYPE AND REACTION CATEGORY
Type of Source
...
Transportation vehicles~
including:. . ....
· Aircraft operations
Local traffic ·
Freeway
Rail
•· Auto race track
Total Transportation
. Steady state neighborhood
· · soi.u-ces, 'including'
. . ·.
transformer:substations, .
residential. air' conditi~ning
Steady state industrial
operations, including
blowers, general ·
manufacturing, chemical~·
oil refmeries, et cetera
.·Community Reaction Categories
Vigorous
.. Threats of
Legal Action
: :6.'
1
: 2'
'· .. ···.'· 9····
. "s.
.... 1
Wide
Spread
Complaints
~. . ·. ·-: -~ .• .
. [.·· 2.
l
..
. 7 ..
.· .. ···--.···
No Reaction
or Sporadic
Complaints
4
3
7
2
10
Total Cases ; _·, .. · 22 . :· .}.4. . 19
.·
D-19
Total
Cases
·12
.9
1 . '1' ·.'
.. 2
19.
7
24 . . ·.
55
·\
COMMUNrry .•. REACTiON·
VIGOROUS ACTION · ·
SEVERAL THREATS····
OF LEGAC 'ACTION· •
0 R STRONG APPEALS'
TO LOCAL OFFICIAi.:S ..
TO STOP NOISE
Wl-bESPREAO COMPLAINTS
OR SINGLE THREAT
OF LE_GAL ACTION
SPORADIC
COMPl.AlNTS ·.
NO· REACTION .
. . ALTHOUGH NOISE IS·
GENERALLY NOTICEABLE
'•:· ...
__ ._-._ ... -, .
·_,. __ .
• ·: •.• -!' '"-~ . ... ~
. ·. ·. ,-..... , ----,.:_.:.; .. -
....
' ,.;.· .. -····
. ·.•:
. . . : . . . .
·.-. ....... -... ,
--~---~-
' .. ' .. :-:l-:.·:
.. :.~ -:; ~-7. -.....
-~_: ·.
• -:~·~. •'.· ,•
·:-·'
Figure D-7. Community Reaction to Intensive Noises of Many
Types as a Function of the Normalized Outdoor Day
. Night Sound Level of the Intruding:NoiSe D-3
·•:.:···
: . that e:idsts in the. absence ofthe identifiable intruding noise; lfris· conJ:lll5ion;:·i;:;-•~1lot 5urpris-
iilg; it simply suggests: that people tend tO judge the magnitude of an intrusion with reference ·
to the noise environment that exists without the presence ofthe-intfllding noi~e source. .
· The data in Figure D-7 indicate that widespread complaints may be. expected when ... ·
the normalized value of the outdoor day,..night sound level of the intniding·noise exc¢eds'
· •· that existing Without the intruding noise by approximately:S dB, and vigorous community
·reaction may be expe.cted when the excess approaches 20 dB. The st~dard deviation of
· these data 1s3.3 dB about their means-and an envelope of±S: dB encloses:approximately
·· 90 percent of the cases. Hence, this relationship betw.een•.the normalized outdoor day•night
· s.Jund level and community reactionap.pears'to be a·reasonablyaccuratearid useful tool
in assessing the probable reaction ofa community to an intruding noise ~d,;irt obtaining one
· ·type of measure of the impact of an intruding noise· on a community. ·
The methodology applied to arrive at the correlation between nor.nalized Lctn and
community complaint behavior illustrated in Figure D-7 is probably the best available at
D-20
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present to predict the most likely community reaction in the U.S. Unfortunately, readiness
to complain and to take action is not necessarily an early indicator of interference with
activities and annoyance that the noise creates. The fact that correction for the normal
background noise level without intruding noise results in better correlation of the data
points might be interpreted to mean that urban communities have adapted to somewhat
higher residual noise levels that are not perceived as interfering or annoying. On the other
hand, it is more likely that the higher threshold for complaining is caused by the feeling
that highenesidual·noise is unavoidable in an urban community and that complaining about
"normal" noise would be useless. For the present analysis, it might therefore be more
useful to look at the same data without any correctio~s for background noise, attitude, and
other subjective attributes of the intruding noise. Figure D-8 gives these data for the same
55 cases.
The increase in spread of the data is apparent in comparing Figures o .. 7 and 0 .. 8, and
the standard deviation·of the data aboq:~ t!le mean value for each reaction is increased from
3.3 dB for the normalized data to 7.9 dB. The mean value of the outdoor day .. night sound
level associated with ''no reaction" is. 55 dB; with vigorous reaction, 72 dB; and, for the
three intermediate degrees ofreaction, 62 dB. · · ·· · .
COMMUNITY REACTION
VIGOROUS ACTION
SEVERAL THREATS .
OF LEGAL ACTION
. 0 R STRONG AP.PE·ALS .
TO LOCAL OFFICIALS
TO STOP NOISE
WIDESPREAD COMPLAINTS
·.oR·SINGLE THREAT
OF LEGAL ACTION.
SPORADIC
COMPLAINTS ·
NO REACTiON
ALTHOUGH NOISE IS.
GENERALLY NOTICEABLE
·,·· .. ·
. · ..
• •....
• ,_.
•
•· ::· .. . ... . :. .. .
· .. ··
.. . .. .. ·• •· ••
• • •
••• :··
• . . . . .. .
.···.· . . . . . . •
•••
. •·
.. ·. .
•
•
.. ·. . •.-.. -...... I....I..~.......J..---..1---.,..1--:--...L...-_;_..J....._~_,_,.......L ____ L...-_J...-----.I
40.. . .80 ·90 •.
. • 9lJ.TDOOR DAY NI.GHT:;souND LEVELOF-INTRUDING. NOISE ·lN dB RE 20 ~;i~·~OPJ\SCALS . . ..
... ,: ·.···
.Figure o .. 8. Community Reaction to Intensive Noises of Many Types As
. AFunction o.f.the Outdoor Day/Night so~d Level oftlle
I~tr.uding Noise 0 •3
.·
0..2l·
. ::····,.,.
. · . ~.
·· .. ·
There is no evidence in these 55 ca,s~ ofeyen,.~poradi_c :complaints if the Ldn is les,s.
·,than 50 dB. · · · · · ,.. · · ·
.'-:;.
., .. '· ., ,;.4·.,. · ...• ·.:;·:!·.·
•, -·:····. :· ...
· .... , . ·.
· .. : . '·;:;:..;;·::·:~~ ....... '. :·· ·.· ;.· .. · .. · . . .. ~ . . . . ~ ... ,;
. . : ~ .
.. ·;:
The results ~f ~ciological·surveys ~e generally stat~d iri terms oft)le percentage of
respondents expressing differing degrees of·disturbaitce or dissatisfaction due· to the noisi-
ness of their environments. Some of the surieys go into-.a'complex procedure to construct
.. · a $Cale of annoyance~ · Others report responses to the direct question of "how annoying is
the noiSe?'~ Each social survey is related to some ldttd of me~ementof the noise levels
(mostly ftom.aircraft· operatio~s) 'to which' t~e stirvey respondents are. eX:pos~d, ·en~bling
correlation· between-annoyance· and; outdoo~ noise levels in residential.areas. ·.
. . ···.··-·· ·· ... -~----:. : .. · . . ' . ; .• ..
.·;··, ...
. ·.· ...
...
.··. . The results of Social surveys show that individual responses yary .widely for the same .
n·oise leveL · Borsky·D-t' has shown that these:·variari~~s.are red~~ed substantiallY Wh~n: · · ·
groups ofindividuals having siinilar attitudes about ·•:rear-• of aircraft crashes and ••mis-" . . . . •.·:.
feasance" of authorities are considered. Moreover, by a:veragirig responSe& over entire sur-
veys, almost identical functional relationships between human response and noise levels are.
obtained for the whole surveyed population as are obtained for the groups of individuals
having neutral attitudinal responses. Theref<>re, in deriving a generalized relationship be-
tween reported annoyance and day-night sound level, it' seems. reasonable to use the average
overall group responses, recognizing that individuals may vary considerably· from the average,
both positively and negatively depending· upon their-particular attitudinal biases. In most ,
cases, the average group respcmse 'cari also be' interpreted as the average individual's response
during his life period. That is 1:o say, each individual changes :his attitudinal biase~ 3 ~::or d-
ing to various factors and personal experiences not necessarily connected to the nc:se 'Jr
D-22
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even to the environment in general, which lead to fluctuations of each individual's attitude.
The average group response does, to some extent, express the individual's response aver-
aged over longer periods of his life. Therefore, this response reflects the effects most likely
to affect his health over a longer time period.
A ~omparison of the results of three of the most prominent social surveys around air-
ports are presented in the following paragraphs. These are the first and second surveys
around London's Heathrow Airport, 0.6,D-ls and theTracor study 0.7 around eight major
airports in the United States. The noise level data reported for each survey were converted
to outdoor day-night sound levels for the purpose of this analysis. In addition, data are
presented from a survey of response to motor vehicles-in U.S. urban areas.o.u
First London-Heathrow StirVey ..... .
The first survey of about 2,000 residents in the vicinity of Heathrow airport was con-
ducted in ·1961 and reported in 1963.0.6 The survey was conducted to obtain responses
of residents-exposed to a wide range of aircraft flyover noise.· A number of questions w~e
used in the interviews to derive measures of degrees 'Of reported annoyance. Two. results
of this survey are considered· here. ··. ·
A general summary of the d~ta, aggregating all responses on a category scale of annoy-
. ance ranging from "not at all" to "very. much annoying," is-vlotted as a function of approx-
imate Ldn·.in figureD-~. This figure prese11ts a relationship between word d~scrivtors and
day-night.sound~leveL · ·.·· ·· ..... ··· ·· · · ···. ·. · ···· ·· ..... . ··
.· ...
Among the respondents in every noise level category; a certain percentage were classi-
fied in the "highly annoyed" category.' This percentage. of each group is plotted as a func-.
tion of approximate·Ldn on Figure D-10~ . .
CompariSon' of the data on the two figures reveais that; while the average over the
population would fit a word classificati~n of "little anooyed" at an Ldn value of approxi-
mately 60 dB, more than 20% of the population would still be highly annoyed at this Ldn
·value.
In addition. to the derivation-of.overall annoyance scales, this study examined the
attitude -of the people towards their area and thefrdesire. to move as a-function. of.both ..
noise level andseveral other factors. The results are suminariZedinFi~ n..:11 and D-'12~
They indicate that when the· approximate Ldn exceeded 66-68 dB, aircraft noise became
the reason most often cite<i by those who either "liked their area less now thart in the past" ··
or "wanted to move". Further, .the data indicate that aircraft noise was of little importance,
D-23
w u z < >-0
~ VERY
< ·MUCH ....
0
Kl w
~ •C) MODERATE' 3
w
0
·z
0 z ··LITTlE
0
~-'.
a.. O·'·NOT AT
w All
(!)
'<' 8:i > <
2
"·'··.,
: • .. ·.··
.. ··.····
.•:"
':;• :···
.· ....
.. :.·.·.
Figure ·D-9. Average Degree of Arinoyance as a Functio~ ~.fth~
Approximate Day-Night Noi~ Leve~ ..:.· Re~ults,of-F~t.' .. ·
, ,._ l,.ondon ifeathrow S~ey0.39f:rom:~ · ······'· ..
:· • .-... ·: .. ···:·\-·,r::··(·
.: _,:._..'. : ·.·:·• ....
COIDp~ed tcf other· environmental fac;tors; when:the approxfuiate' Ldri W·aS:below 53 dB and
--·--\\'~s.or~verageimporta~ce~_afactor.whe.p;,,~he~p~()Xln,late·Ldrfwas.6(l~B. .. ' · ,··.: ....
. . . . ... '. . .. · .... ·. ,:, ..... _· .. ·. . ' :. . ..:··'
,_··.•:;''
(·
· · Results of Second London Survey and Tracor Surf~· ··· ' ·
,·-... ;.· ..
:.·:_· .. ,
... , ... , , .....
. -.. , .. ·.. .. . . . . ·-.-~:::·: .
ln l967, a second 8urveyD-~-s was-taken around·~Heathrow Airportinthe·same gerietal.
area as the fJ.rst survey~ While refmements were attempted over the fltst survey, the results .
were generally the same~ In 1971, the results of an intensiVe three year program. under
NASA sponsorship which studies eight air carrier airports-inthe United Stateswete·reported
by Tracor. !>:.?. Since each of these :efforts is discuSsed fu detail in the refere~ -only an
.· analysis of theit combined· resultS is conSidered here._. Bots1cyM7 used the data fiom. these
. studies to correlate annoyance with noise exposure level for-.people having· differentatti.:
tudinal characteristics and· differeD:t de~ees·of annoya11cer · · · ··. · . · _;·_ ~-:: ._.. . ,:.: · . · . · ··
o.-;24 ..
..... :
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60
-o • >-g
c <
>-40
:::c
Cl
:I:
:.e 0
20 .. ~
~·
. •, •." .:.•··.
I ... 00 65
.-.;. .. · .
70
.... ·
···_;/'
~.. . . .. : .. :
. 7.5
. Approximate. Day::r-fight Average Sound Level, in Ldn
. . . . . "' :· . . . .. ' . . .
Figure D-1 0. Percentage Highly Annoyed as Function of Approximate
.·Day-Night Noise Level~. Results of First London
Heathrow SurveyD-39 from o-6
··,
.... , ···.······ ,_;,, •.·
•
so
Uti.lizizig Barsky's data for ''moderate" responses.to. the attitudes of "fear" and "mis--
feasance"' the relationship between percent highly annoyed and noise exposure leveiis ..
plotted on Figure 1).13. Again, .noise. levels have been converted to approximate Ldn
··values. It is worth noting tfuit more than 7500 respondents are included in the data sets
from which;the. computations were derived •
. ·· ...
, ·.:
The comparisoi:r·beb.veell·th~ .rest!lts:shown on Figures 0~10 andD-lJ·is•striking in.
· · the near ide~tity of the two regressionlines.,.....indistinguishable at any reasonable level of.
statistical ~nfid~n~e;_ The importance of these two sets of data lies in the stability of th~
·· ·· <results. even.th.ough t~ data wer~ acquired6 to 9 years apart, a tiline different airports in
. . . ,.. tWO different ·COUntries. ThiS complete agreementled tO· the proposaJ of.an average curve
· · · · · for: the :rioininahelationship between ·soWld lever and percentage :of people annoyed, which
·has: been cooi.dinatedamong.and•:osed·by various U;S,~Govemment agencies, D-19 applied in
. ·the studies oflC.bLQ's coordinating committee on aircraft noise; and verified by a recent
.· analysis ol:British; French aniDUtch survey results ·conducted by the Org<Ulization for
. Econom1c:Cooperation and Devclo'pmerit (OECD). D-zit · Accof9ing to the,OECD work,
D-25
··: .·.
::·-· ..
·QI
>
0
::E;.
0 '1-
,,•:"
Figme D-11. Percentage of P¢ople l.ikirig Theit Area Lesi,Now
· than in the Past forVarlohsReas()ns: D-6 : :.. .•:
. :·.-.··.·· :-:.:·:·;:=.: =.c.;r·= ·,,._,.,
't:l· .
. · ~ 35, (.. .--+.;..;....----!~-~-+----+---+...,..;
s::
llS
3
0 .s::
3
~·J:o·
Q. g
c..
Ql
..s:: .
.: 2'5 ~---+--..,.+.,-=' ...... ~ ,-+-~..;....o;j.~~~......,;.~....;.
·o
Ql
C)
llS
-4-0 s::
~ 20 L---.. --~ __ _. __ ~ ____ ._ __ ~--.. ----~--~----------~
~ ~0 50 60 70
Approximate D:rtv-Night Average Sound Level (Ldn) in dB
Figure D-12. Percentage of People Giving Particular Reasons.
for Wanting to Move ~6
D-26
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60
40
.• Appro~ima.teDay-Night Average Sound Leveh~dnJ in dB.
Figure· D-13. Combined Results-British and U.S. SurveysD-17
. :.·.
the pe:r~entage of annoyed people can:he· predicted as follows: Percentage of annoyed
people = 2 (Ldn-50).
The results of the Tracor.Study D-7 also give· a relationship between the number of
people who indicate in a soCial survey that they are.highly annoyed and the number of
people who indicate that they have ever. complained aboutthe noise to any one in author-
ity: The· results; presented in Figure. D-14, indicate that. when 1% of the·· people complain,
17% report being highly annoyed; and when 10% ofthe peopie complain, 43% arehighly
annoyed;. . ....
...
Judgement ofNoisiness.at·Urbali ReSidential Sites
noise for:the A:utoniobile Manufacturers Association. IH As part of this. survey, 20 different
urban-suburban.residentiaUocations no-t in the .vicinity.o[ airports were studied in Boston,
Detroit,. and.Los Angeles. Noi~~ rneasureinents-wer~ acquired and a social survey of 1200
D-21··
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. ' .... -.. ···
70~------~------~-------r~-----.-------r
........ . ./.·
--·· .. · ...
··:• .. · ..
·;.:
.. ·-.. · .·._. . =.·.:.._._:
·._.·. ·.· .. _,_ ;:::. :. ,··.:·: .. -;._
A·-cl. Cia·
-.3·--;~---. I ~-· r
Sy/X' ,_,<·
' ~; •:
0~------~--~--~--~--~~------~--~--~ o~ s · · 10 ·''15'-·-. 2o·:
· Per-cr;!nt Complainants (C)
Figure D-14. Percentage ofHighlyAnnoy J As A Function of
Percent of Complainants D-7
D-28
25
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respondents was conducted: Part of the survey was directed towards obtaining the respond~
ents' judgement, on a category scale, of the exterior noisiness at their places of residence.
The averagedjudged noisiness value_s per site are plotted on Figure D-15 as.a function
of measured .. Ldn-values.. The significance of these "~on~airtraft" data is~die·com{iarison·
they permit. with other survey data a~q_uired exclusively around airports~ l'ntercomparison
of these data with previous data indicate that for an Ldn value of 60 dB, the site· would be
judged .. quite" noisy. The average.annoyance for a group _would be classed as· "llttle,'' but
about 25o/~--of.the people would still claim to be highly an~oyed.
·: ..
VERY. .5 NOISY
NOT.
AT
ALL
.. ,; ...
-•· .. . ~· •···._··-~-. ~:·· . •
•
·····-··· . . . ·. ~ . . .. . . .
45 . . . . .
·. ·.. . . . : ;-. \ ··:Measure~ Day-Night· Avera,g·e Sound· Level~d~ in .dB·
,.·; .. · ··· ... ··
·Figill-e D-15. Judged Noisiness at Automobile Manufacturers
Association Survey SitesD-9
··.:· ,· ·:· ..... . .-.····. . •' . .. . : ~ ·.· -;.•
75
When an·respcinc:lents~ irrespective of exposure-~te, were asked whether they were
annoyed by ~otor: vehicle noi~, 53% .were not·artn:oy~d, ~iute 46% were,. with an average . ' . . . ·'. . ·.· ..
iL ~ensity ofannoyance. o( 4.2 on a scale where 3 stood for "-quite annoying," 4 for "defi-
·:· .....
nitely annoying"ind 5 "stron~yannoying!' .. Ofthe 46%ofrespondentswho stated they
were annoyed by-motor vehicle noise; 77%-experienced annoyingnoises.while in their homes,
12% while in 1:;ansit; and only. 5% at wo~k. . ·
D-29
........
-;:-;...
. This indication, that the principle annoyance with envll-onmental noise occurs in the ·
residential situation iS further· confumed· in the results ofthllondort City Noise· Survey o-.t&
. sunun.arized in Table ~9. · · · .. .. .:.''
•·..;.·····,··· ··· .. ;·_
.:.'· .. ·'
····· .".'·.· .
... ,..
.. :.-::.'.'.::: .... : · •.. ···
. : ·. ::~ '
. Summary of Ann~y~ce Survey Resmts ....... · ... ;:. ·.··'· ... :·
·>· '.····'·· ......
The· relationships atnong~per~ntcomplru.na:nts ·arid· percent highly an~ye,d_.(Figure
D-'14) together· with~ th~ combined· results of the·two Heathrb\V surve:YS,AA~Ltbe Tt~r
· · survey (Figures o-to· and D--13)liave been combined 'in Figure ~16 to·produ~ a'.general·
· summary relationship between da:y-J:tightsound level~ percent complainants and percent
highly annoyed. Also included in the figure .is a $cale ofthe relative importance' of aircraft
noise as a factor in disliking~ area or wanting t~ rito~~ (Ftgtires D-11: and D-12) imd· the
average values of the three main cominunity noiSe·rcaction categnries(J<'ig:u.re P:-7). :.-:· ..
. . . .·.·:·: :·. ..·: ·...... ·. ·. . · .. ·· . ,, ...
. . .
The resultS indicate that-beiow an.-outdOor day"night 5ound levelotis dB;less than
.· .. .1:% of the ®l1~holds would be. expected to· oomphlin,. alth()ugh 17% of the. pe6ple may
:,; fesPond as fughly annoyed when·questiorted fu a social su.rVey. "No rellCtian" would be
expected in the average community, and noise would. be the)east unportant'faetor in atti-.
tude towards neighborhood. Whe~ the o~tdoor Ldn .ls 60 dB, ap·p~ox~ately 2% of the
households might be expected to complain, although 23% of the people may respond as
highly annoyed when questioned, and sc;n11e reaction would be expected from an average
· · community. IftheJevels· in~rease over 65 dB, more than 5%·may be expected to complain;
a~d over 33% would respond as highly annoyed. Increasmgly; vigorous community reaction
could be expected; and noise becomes the dominant ractO'r in disliking an ar~ ·
.. . ·.· <···. ··. • ...
Table D-9 ...
··.· ...... : .. ;'.-... :: .·. .·.;-... : .. ··
PERCENTAGE OF PEOPLE : ....... .
·.· .. WHO WERE EVER DISTURBED sy·:NOISJ::AT HOME.,'.:.·.-.. ·
.. ··, · .. ···oUTDOORS AND AT_WORK IN LONDON-CITY SURVEYD-ts
At Home Outside At Work
Disturbed from time to time 56 27 20
Notice but not disturbed 41 64 70
Do not notice 3 9 10 I '-"'
-----·
•.:.:.·:···:.:· .. :
. :··· ··:·::·• ........ _.;:.·.
··-.,
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Pelative Importance of Aircraft As A
-Factor in Dislikinq Area or Wantinq to
Mlve (Heathl:I:M 1st Study) D-7, D-10, D-ll, D-12 ard D-13
oL-.:.:.:::.,....:l~---~"-------1.........;-~--.....J.....;..._~
60
Q
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20
. 50. .5.5 . 60 65 70 75 80
... OUTDOOR .DAY.INIGHT.SOUNO LEVEL(Ldn) IN dB (RE 20 MICRil-
•. · · .· _ .. -., .. ,·._,::,.•:· ·· •. ····PASCALS). , · . .:. ·. . .
Figure D-16 •. SummarY()fAnnoyance Survey and Community
· : Reaction Results
,. ·--.. ·. . -. .
. . . . ~ ..• ' .. ' ·. ' . .
It is. importantto keep in mind that the annoyance/tolerance limits obtained from the
social sun~y-reSults havebe~ri ·fourid -t~ be ba5ed.orirelativ~ly ~ell defined heaith and wel-...
fare criteria: the disturbance of essential daily activities.D-19
· 'VARIOUS PRIOR RECOMMENDATIONS FORACCEPTABLE SOUND LEVELS
·:-. ··• ;, :: -.~ .· • ... ·· ····; .. : .. ·.
Reco.mmendedvaluesfor acceptable sound levels in various types of spaces have been·
suggested_ by a number of authors over the. past two decades. These recommendations · . -' -.
·generally have taken into consideration such factors as speech intelligibility and subjective
judgements b)rspace occupants. However, the fmal values recommended were largely the.
.· result of judgements-on the part ofthe authors, which in the case of acoustical·consultartts, •
have been motivated. by the need fat design values which will be on the-"safe'• side. One. . ··
. . . --. . . . .
of the earliest publications providing. recommended values. in modern terminqlpgy was that . . .. . . . . .. -'-
D-31
. · ... ,·
. . . -~-
···=:'.'.·:··.
' ' ~ ,; . ''·'
·.·::-... :-·;' . ·.• .. ·-: ..
ofK.nudsenand Harris Mr in 1950~ ltis.of'interest to.quote fromthetextto·under:stand ....
the reasoning used to·develop the r~~~mended levels: .. ··. ·. . .. . . · ""'. :,, ,. ·., .. ·. · .
: . . . . . . . . . . . . . :. . . . ~ . . . . ·. . . . . . ' . ~ .. ··
.. . .. · .. ···.":'_.,:_. ... ·
. . Acceptable N<>ise ·Levels iri Buildings:· · · ': ···.: .:. ·. · · ·· ·.· · ·' ·. · ..... ·· .... -·._, .. ' -.: ·:-:-·-·.......... . .... :-.. :--.. :.--···
',.·-::--::
. ·. :-.· :• ~ 'The highestlevel'of· noise within a bUndihg mat neither disturbS . . .
.-· ..
···.·····
; .·'its·occupants·nor impairs its acoustics is called'the•acceptable noiSe··::···. ~.······;
level. It' depends, to a large extent, on the iiaiilre of the noise 'a,p.d on · ..
. the type and· customary use·ofthe buildiii&F'rlie. time fiu~tion of.
the· noiSe is one· Of: the.-inosf i~·~t. fa-eto-rs·in· detei1ninhli·its·_t0Ier-i·. ·· · · ··
. ability, For example; abedrooiri with an average noise level of 3S dB;: ... ·· ..
. with no instantaneous. peak levelS s.ubstantially· higher,. would be much··, .. · · · ·
more conducive to sleep than would be a rooin with an average noise
level of only 2S·dB but in which the stillness• is pierced by ail occasional:·
shriek. Fuithermore,levels that ate ann()yingtoo~e·,person are Un"'' ..
: · · . . . noticed by another~ It is therefore·UnpoSsiblcdo specify precise v~ues .
within w:hich·the· noise-levels:should fall m:ordertC>.' be acceptable .. It'' ...
is useful, however, to know the range ofav.erage noiselevels that.are
:· .. -, __ .
·acceptable under average conditions. Acqmpilatipn of such levels · ..
. .. . . ·for various types ofiooms in which noise ronditions'are.likely.tobe a significant. problem is giveri iil [T:ab:le· D-:1.0. *]. The recommended
. acceptable noise levels iil this. table. are empirical values based on the .
experience of the authors and others they have conSulted. Local
conditions or cost considerations may make it impractical to meet
the high standards inherent in these relatively low noise levels. Iri
more. than 80 .percent of the rooms of some of the. types listed, the
prevalent a\ler.age noise levels exceed the recommended acceptable
· · ·levels~ However; it should be understood· that the acceptance of
higher noise levels incurs a risk of impaired acoustics or of the com:.. '···.·
fort of the individuals in the room.
.. · ·.. . . .Since 1950 reconUn.endations by a number of authors,. a's well as nationatstandacls,
. ·. :.,.have been presented. Eighteen of .these rec01nmendations are. tabulated in T'.role · · .. · · · ··.·.
D-10)>21 through D-38 . It is. encouraging to ·note .the cqnsistency displayed, ~lthpu·gb. Iitany
ofthe la:~er :recom.mendations may be based oil th-e recommendatiOns of the earlier
~ .: :authors~ .
SUMMARY OF NOISE INTERFERENCE WITH HUMAN ACTIVITIES AND
RESULTING HEALm/WELFARE EFFECfS
· · · · · .. · ... The primary effect of noise on human health and welfare due to interference with
activity comes from its effect on speech communication.
*These values are given in the fust column of Table D-10.
D-32
--~ ' ..
. ·.-:;·.;·· ·, .. --
·.-.. ···.,· ...
."-··-·.:·-···
-: ; ·• ~-~ _. .
: '•.
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llll.M
PRIOR RECOMf.4ENDA'fiONS OF SOUND LEVEt,S JN V AIRIOUS SPACES o-21 throus" D-3s
Aususl IO;t97l
R~COMME.NDED 1\C~EPT ADi.l!. NOISE LEVE.LS .·.
Switzer· Czecl1o· West
knudSen-' '·.·. Kost~n-l:md slovakia Germany
·Harri~ : tkrantk Berani:k Uwl-cnce ·.ilanOs Aslirae ~nisi,~ J(zylcr Tokyo USSR lk'ranck flu: lie Wood: Rettinger S\lledcn 1970 1967 1968
1950 . 19S3'· 19S7 1~62 ··1962 '1967 1970 1970 1971 . 1971 . l971 19H 1912 . 1973. (p·9) (p-4) (p·IQ-11) (p-12)
I.; 2 ... 3 4.. s.' .6 7 .'•. 8. 9 .IP II 12 IJ 14 IS 16 17 18
db(Aj .dBII\t dii<Ar.· d~IA) dD(Af .dD(A)• dU!Al dQ(AI dBIAI ~II(Aj dB( A) dDCAic dD(A)" dB(j\) dO( A) d8(A) dB(A) t..,,l 'M-Il
R~SIDENT: ..
Home 3S4~ BedroQ~ 3S-4S 35 ····:d~· 30 2S-3S. 40 3S 34-47 3S-4~ 3S 34-42 25 3S-4S 40
l.iving ~09in 3HS 3s 3S 30-40· 40 )5 3H-47 40 2S 3S-4S 40
Apartment· 35-45 ~-. JS-40 . ~Q 3S-4S 18 34-47 38-42 . 3S-SO 40
Hotel 35;,45 ·:: .. : 3S-40 ~S-40 3S~45 . :i8 3S 34-47 . 3S-S4 3Q-40 42 3S-SO 40
COMMERCjAL
•:.
Rcsli:lurant so-s~ ·. s~· ~s <jo,{,o· .. so 4P-SS ss ~s 4.2-S1 .45-60 45-SO so 4Q-50 ss
.Privale orpce 4Q--4S so 'J0-45 .JSC4S · 3o-4s 2Hs '40-4$ 3S 38-47 30-45 .40-45 46 40
(tem:ral orn~ · 4S~ss 411,-Ss .• 4Q-6o 60 35-65 5(1..{,0 JS-40 ,. so 4:!-S1 4S"S5 45-55 50
Tr.~n,s.port.:· ... '· J5-SS . (.0
INDUSTRIAL .
tr' Workshop.:
40-6ii SS-1.5 4S-SS w Li~hl so S:!-<•1
w ll<avy 7S 6Q-90 70 85 1>6-HO l!()-75 70 SQ-60
EDUCATION ..
: Cla!io~fOOnl· '._ 3s-4o 3~ 35' }0-40 . JO 3S-4S 35 40' 3H-47 3S lS-IS 38 35 ·3S-4S
··loth,jratorY ·10:50 ~o"so · 4lt-SO 47-41• 4S·+.'Il 4~
"·libl".&f)' 40-4~ 40 4J~4S JS.,4S .\s ~Hs 40 .lH-47 4Q-4S 40-~S 42 40
HEALTH ·' :·.
llm1li11il . 3S-40 40.-4'~ ~Q-JS j; 3~~5 40 2:5 H-17 40 40C4S 38 2S-3S ~S-JS 35-10
RH'R~AT!Of'l
: ~wimpool .45.:.h0 SO"bO so
q-:;o Sporls (~lllpj.) (•.0 30 J,_ .. , (.0 1.0 46 1•0
11>11> Ciy1nnasillm S5 40-50 5S-<.o 45-SS 46 "''0 -.,
AUDITORIUM ' Olo
<0.. Ass<mbl¥ llall 35-40 3S 3S-40 ·-40-45 30-10 ··'" .lQ-42 JS-4S 3S-4S
Ql c Churdt ~~=1~ · .. 40 . 40 3S-4o 3S i~-35 40 35 3Q-4' JS-40 3s,4o 3K-42 \ -·n -11) Concert tlail 30-3S lS-3S 2s-1s JO 2S-JS .'!H-1\5 2)-30 25-35 30-3~ 34 35 ~0.. Cm!rt Ro,,un: 40-4S 40. 4(!'45 '40,45 3S 40 42 JS-40 3S~40
ii" Rc..:ord SIUdio 2s·-Jo · 30 2S-JO 2o-3o io 2S"JS . 2M 21-H 15-30 .30 30 ., 1 V Sludici ·· 25-30 JO 30 2,1\-Jj 30 2S-3S 2a ~1-.H 3(}..3S ·-·~ 34-38 no Mor. l1ii.:l. o3 Slllliio ·• 2S-~0 30' lS-30 2S-35 28 21-34 3S ·u· \
'0 MlH.I1ict .. : ~ liu:alcr; 3s-4o : 40 40 3S 35.-4S 40 '~o 40 J5-4o'· 38
L!!\:. l"hi!.UI_~t lll-lS 35 30-35 2s ·30-40 33 3().34 3o-js 34 35
OUTS Ill"
ltui-al 3S-45 35 3S-15
St!bUib . 4Q-SO 4S 35·50
lhlliU} 50-110 41HS
lu.lu!ltri.i.l 50-60. S0·6S
ltcs Ail' aS 55
Neill SChools :. ·
llu~ilih&is"·. : • · ~(:. , db(Af = MC = U)
·. •6 dO greal<r .I han AIISRA!;'S died MQ ..
'... .. :.
........... · ..
The levels that -interfere with human activities~which do not involve active listening
. . cannot be quantified ·r¢1atiy~ to the level of, a desired· sound. ·Rather, thel~vel of a.Il. intrud~ ..
. in:g sound that Will· cause an iitterference depends upon its relation to. the.clevei•ofthe other . - .
. . background' sounds m. the envil"onment and-the stat.e:()fthe'huirian aud.itoi.,.:e·.i;the degree
.. :· of concentration w.q,e~ .. enqelivO:rifi:g. t-o· aCt::()mpliSh .a/ i,hciltal taSR', or tht(~pth. of~h~ep, et~ .: •. ·.·· .
... ::
. ...... · ... · ...
The levels .of environmental' rioistHhat. are associ1lt~d with annoyance depend, upon
local.eonditians·and attitudes. ·They·• cannot be·cleatlyidentified in tennso{·the·M'tional· ...
public health_and welfare. Tlie O:n1Y.le~el,s·which~.b¢.~o~clentified'are:~ihe:)e¥,els.whi,ch.:
are requ0.:dto assure that si)eeCh oommunication,in .. the.hOme·and outdoors .. isadequate ....
·iri terms of public health an4welfare •. Lpwer levelunay b~.desirable and appropriate: for ·
specific local ~tuations. · •· • · . . . ... , · · . · ,._ · ·
·· .. ·:.;. •· .. · .... · .. ~ .. ···. . . . .. · .. ·. Thidevel-identiired fo~ the. protei:tio~ ~f ~~K:-~mlri9~i~tion·j;·_4.i.(ifi~i~iilinhe
home. Allowing for the 15 dB reducti~hin sound ie~ei bet~een outdoo~· ~d indoor8, this
level becomes an outdoor day-night. soiUid; level' of 6o dB (~e ":to. inicropas.cal~) fo~ residen-.
.. · tial areaS.· For outdoor voi~ cotritnuruca-tion;. the :oUtd&r d~y~night level-of -60 dB allows
normal conversation at distances up .to. 2 meters wit1iQ$%..sentence intelligibilityi .. . . . .· ': ··.... . .. ::· . . · .. :. . . " ··.. . .· .:: ·. ·:,<:. -~~: ... :. \;.;.·,:·.-'·;,-:-~ ... ·.,-... .. ··.~. ··.· >· ·. · ... ·. : .....
Although ·speech-interference· has ·been identified a~ the pr~ary interference o_f~oise
with human activities, and as one of the primary reasons. for· adverse ·community reactions ..
to noise and lting-term annoyance, a margin of safety of 5 dB is applied to the maximum
outdoor level to give adequate weight to all of these other adverse ~feet~ . . . .. . . .
. Therefore, the outdoor day-rrlght ·sound level identified· for residential ~easis a· day-
night sound level ofS 5 dB. · ·· .. · · . · · ·
. . . 'The associated' interior day-:-night sound level Within a-typical home which resuits from
~utdoors is IS· dB less, or 40 dB .. The ~xpected indoor daytime level for ;~. typical neighbor-
·. h~d which has an outdoorday~njght soimd·level of5$.4B:is,approximat¢1Y40 dB, whereas'···· ·
, ·.the nightrune level-is· approximately 32 dB' (~ee Fi~reA-7.)~ ThiS latter value is•consistent · ·
. .. with the limited available sleep: criteria. o.s Additionally, these resultirig indoor levels are
... · consistent with the background levels inside the hOme and which have been n:!cornmended
by acoustical consultants as ''acceptable" for :tnany years (Table D-1 0).
The effects asSociated with an outdoor day-night sound level of 55 dB are summarized
in Table D-11. The summary shows:
1~ Satisfactory outdoor average sentence intelligibility may be. expected for
-normal voice conversations over distances of up to 3.5 meters;
D-34
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···----/ . ~. . .·, .: -. . . : :· .. ~ ·.: . . . .
··.'. ·.
Table D-11
SUMMARY OF HUMAN EFFECTS
IN TERMS OF SPEECH COMMUNICATION, COMMUNITY REACTION,
COMPLAINTS, ANNOYANCE AND ATTITUDE TOWARDS AREA
ASSOCIATED WITH AN OUTDOOR DAY /NIGHT SOUND LEVEL
OF 55 dB re 20 MICROPASCALS
Type of Effect
Speech -Indoors
-·Outc,ioor5 ·
~-.... . ....
Magnitude of Effect
100% sentence intelligibility (average)
·with a S:·d:B ·margin· of safety
100% sentel1ce intelligibility (averag~)
at 0.35 meters
99% sentence intelligibility (average)
, . at 1.0. meters
·· · ·· 95% .sentence intelligibility. (average)
· at 3.5 meters
< ..
-,·' .. ..···.--
Average Cornmunity Reaction None, 7 dB below level of significant
Complaints. >
~ . . . . .
... , ·:-· , .
. ; .. · ·. ·· ...
.. Anl}oyance • ·
······-··· ·. -· ..
Attitudes Toward Area
:,·
.-.-'.
·. · .. ·· ..
: ''"complaints and threats of legal action" ·
.. and at least 16. dB below "Vigorous action"
.. (attitudes.and.other non-level related
. .factors may affect this result)
1 %·dependent on attitude and other
.·· · · · non-levelrelated factors·
. ::··. : >-. : ..
• ' . c .. 17%-.dependent 'on: attitude imd other
non-acoustical factors
. ... . · . . · .. ,_, . •,. ~ : . : ·•
. Noise essentially least .important of
.. •·.•• .. .;-'."·.1-·.·.-: ·.· vanous 'factOrS ..... ,·· ··:-·-.
_ .. _, .. ·.·-· ··.• ·.
~-: ·.·• • .. '• .....
D-35
--.-_ .. ,·
~ ... , .. ' .... , .· ....
.. ,··.·:··:.
".i
.. ·· ... _,:-'··-:···:····
2.. Depending .on attitude and."other· non-~Cb.tisti~ factors, the average expected ' ·
community reaction is, ~·none'.' although 1% tnay;complainand:·l7%.indicaie
••rughly:~noyed .. ;whep·r~i)ondingto·.~-~eyquesiions;.and': ·· ... ·.· ·
3.· .·. ··Noise·~;the.lea~t~(}rtalll .• f.a:~or~~~rilin~.:~~iit~~~-toJ::.::::::~a.
. . . . . . .... : .~ . :·. .
' .. ~ ·:.1 .
·:.:· .. (,'; . ·. -: .. ':; ..
... · .. ·· ...
Identification of a levelwhich·is--s:aB~highefthariOthe: 5SdB identified abOve would ... ·.
sigfiificantly· increase the severity· of-the a<verage coinilitirtity r.eactio~. is. well as· the expected ._, ..
.· .··percentage··of.: complirliitS .. and·~oyance.: ·.Con~~ly;·~.q~n,tifreation•.ofitcJevei_S, dB loweT. ···. ·
· than. the·: 55 dB identified above wouid:.red-uce·the indoor le~els resulting from outdoor · · ·
. ··.noise well below the normal back.grount:t indoors~· It w<lu!c(decrease: speech privacy out., · .
. doors t6 margmal distance •. rihie 'crumg~ in· annoy a~ .:w.:c;uld .be"nlade:siitce,_.~t levels .·
below the identified level; individual attitud-e and-life sty~e,;. ~s well as.;lo~ tonditions, ~e ..
more important .fa~ors" in'con'trolling thefesUit~g ~gnitude of tlle}evel:of the irltruding ..•..
noise. · ·· . .· ·. · · .. · . -~ ··· · ·: · · ·.· . · · .. .. .. ···· ·· ...
··.· ,.· . . .· .,. ~. . .. .. . .
. ... . . · In conclusion, a Ld:n level_ of'S$ dB is-identifJ#l is outdoor level in :residential areas· .. · ·
· .. ·'·compatible with the protection of public.heaJth andwelfar-e~ TheleveLof55 dB is identi-
fied as maximum level' compatible ·with adequate speech communication indoors and out.;
..... ·~ --.. ·.
. doors. With respectto conipWnts and long term·~nnoyance this leVel.iS,clearly a maximum
satisfying the larg~ majority .. of the population (see·T~ble ~11)~ However~•specific local
situations, attitudes, and conditions may make lower)evels desirable for some locations.
A noise environment not annoying some percentage of the population Qinnot b~ identified
at: the present time by specifyingnoiselevel alc;Jn~.:,; :-·. ·• :'>·· ·;: ., ... ·
.. •• : •. :•,!',. · ... _.·; . ... -.. ;,,·_
·.··.::
,· :_:
:<-•. ·-. . . . ~ ·:.:~~:.: . ; .. -. : .. -. . -'·." ; .. :.:·: .. ;_.· ... ;
. ··· .. · ·:·:·.·· . ··-... ::: ·.·,· ·. •···· ~· ···:·<!'.'.'" ....... :;
;• .··
_ .. :.· ~· ........ .
·:: ..
-·.·.:.;;·,·.:: ..
.. ···:·:' . .''
D-36
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REFERENCES FOR APPENDIX D
D-1 "Effects of Noise on People," Environmental Protection Agency, NTID 300.7,
December 1971.
D-2 Webster, J. C., '~Effects of Noise on Speech Intelligibility", Noise as a Public Health
Hazard, American Speech and Hearing Association; No. 4, February 1969.
D-3
D-4
Eldred, K. -M., "Community Noise," Environmental Protection Agency NTID 300.3,.
December 1971.
''Method forth~ Caiculation oft.Q.e Articulation IndeX," American Natiom.U Stand-
·:.· . .;·.-:.· ·. ·.: ........ ··· . ~ds Institute, ANSI 53.5-1969, New Yor~ . · :
···:·::.'···:.
D-5
.·.•. . . : : ... . .···.· .... · ·:··. .· . •; ··:: ..
. :· ... •··:. ': . . ~-.....
"Public Health and Welfare Criteria for Noise,~•Environmental Protection Agency,
. ssoi~73:..oo2,..July 21, 1973. ·
1).6 "Noise,. Final Report,,. H.M.S.O., Cmn"ci. 205 6, London, July 1963." ..
D-7
D-8
Connor, W.: K •. and Patterson, H. R,. "Community Reaction to Aircrrlt Noise Around
Smaller City Airports", NASA cR.~2104,AugUst 1972 .. · . .
Bitter, C, '"Noise Nuisance Due to A4'craft," lnstitut Your Gezondheidstechniek
TNO, 1968. •
D-9 Bolt Beranek"andNewmal1; Ihc.", ''survey of Annoyance from.Motor Vehicie Noise,"
Automobile-Manufacturers Association, Inc., Report 2112, June 1971.
D-10 Rosenblith, W. A., Stevens, LN., ~d th~·St~ffofBolt Beranek anclNewman, Inc.,
"Noise.and Man;" HarrdbookofAcausticNoi.se Control, Vol. 2, WADC TR-52-204,
Wright-Patterson Air Force Base, Ohio: Wright.Air Development Center, 1953.
D-11 Stevens~ ICN., Rosenblith, W. A.;~and: Bolt, R.-H~,: "ACo~minity's Reaction to
Noise:· Canlt Be Forecast?" Noise Control, 1·:63-:-71, 1955. . . .. ·... . . . . .
. : ,.
. D-12 Stevens, 1(. N,., and Baruch; J~ J.;:'~Cemmunity-Noise: and: City Plaiuiing,'' Handbook -· · ..
ofN_oisf! Control, Chapter. 3S,.McGraw-Hill BookCo.,,l957. _, .· , .. . . . .
D-13 PamiCk,_If.b,, •'•community Reaction to N~iSe;"Handbooko{Noise:Control,··
Chapt~r.3.6., .McGra~~l-Book~·co~·; 1_957~.-· ·
. : ... ·_, .·
._ .......
D-37
._, .. ·.
·.;
··•·.
1;)-14
D-15
......
. D-16 ·.····' '.
: ·.-·'.
.. ·: ~·:· ... _. · .. -: ':_,_:·-
... -...
... ·.· .. ,_.._.
Stevens, .K. N. and ·Pietrasanta; A~ C., and the ·Staff ·of,Bolt Beranek arid Newman,
Inc .. , "Procedures for Es~imating'Noise Exposure· and' ResultingGi;limntinity Reac-
tions from Air Base Operation; ••·. WADC TN·-51-1.0; Wrigh:t.;Plitt~rsop. .J\:ir :Force Base;
Ollio: Wright Air DeVelopment Center;l9S1-•. :· · · .. · · · · · ···· ····· · · · ·
-.• .-.' .... ·. ·.·· .
......... : ........... _::: ,·: .... .
'•: .. -·.:.-:·.···,· .. : ... :·
. ~ ....
"Se.c9nd SunteY. of·.AiicraftN9h!e.AJmoyai1:e~ N,a.und 'l.OndonJ:Hea-throw} Airpo_it/' ·
.. H.:t\{~~I(>~:_i~(m4on,. t9_?F.:""i .. ~-.:;,. · · · : :· .. ,·.·; ·· ··.:.· ... · ·· < .. :.: ::-.·:·;: ., ... . . ··· ·
. ·.... ··.· ...
Bitter,-.C~ ."No~e N~ce: Due·~' Aircraft/~ ·CoUogue..~urla,~~i~tio~ des.exigei}'=es humam a.r.e~ du biuit~.Parls,; N~_yem~r-'r9:~~ '·: · · · ··:.:···-·.· · · ··· · · ·
1}.17 Barsky, P. N;, "ANew Field.;Laboratory)w:l~tho(fol~gyfor Asse~~g:Human Re-
. SPonse tO_NOise;". N~SA-CR·2-2:il; M:alcli--·i:9J1'~~·-,_·~_--;-~-~-:-·_·-.:.;-.:· . ·. .. -· ···,--: {, ___ · · -
IH9
D-20
\
1).21
' :. . . . .. . . .. ... : .. : :_ .. ;:~·· -~·,: .. ·;_. __ ·-~~-:·:~· . ; ~ :··.·--~--~:~--:·· ... : ~·;-. -.··':"·,-.:--.::;·:·.~:-:>-:•,_._.,:._:·.··<.--.· ·.. .
•'NoiSe m "I:o:wns,''NQI.S.E:. GhM>t.¢t IV, 22 .. 3:1,. PreseiJ.ted.to·,-Pat:liament by the Lord
Pr~dent.of the Coul1cil' and· Miilistet fot ·scie~ by C6.mniittee dft;fue Pr-oblem of
Noise, July-19~;.1£M~·~o·~~ Lo.ndol},_R~print.OO>"l966~.--_:·_ _, ... : __ . .-::· · . . . ":•• . ,. . . .-
"Safeer, Harvey B.~ ~'Conrtm.tnity R~porise to· NoiSe Relative.t~ :f~nt ofPopula·
tion Iiighly Annoy.ed ·l:Jy'N.oi~;:'. :US· Dep~ntof'Transportaiion, Office of Noise
Abatement TM 72.;;1, June 6, 1972~ . · . · ·· · ·· · · . · ·
"Social and Economic Impact of Aircraft Noise," Sector Group on the Urban En-
vironment, Organization forEc.onomic Co-()pera:tion and Development; A];)lj1 1973.
Knudsen,. E. o~ and' HaiTis, c .. ~.Aco~ticfd'.Desfgnihg'in A;C/iftd/:t.f.ti.e;.New York:
J. Wiley and Sons, 1950• . . · > .. ·. · . : · .. ".: .. ;::: .::~: .·
.·:··· .·•:.···.···-·
P.22 . :Be~nek, L~, Reynolds~-J •. L,_and.·\yilsoni I{...a:, . .-I.'#P~US~1ld·~rQ.Cedu~s·for
· Predicting Ventilation System Noise-,'' JASAt v. 25.~ no. 2.: 313~:· 1'Q5'3~: · .·· ·
.. .. . ,. . ·. . •· .. :-_; '· ... . .• ·.• . : .. :_-_,;;_ ·. ·: ..
... . ..
. D-23 .. ·Beranek, L, ••Revised Criteria for Noise in Buildings," Noise:Con-tT~l. v; 3, no, 1,
1957.
D-24 Lawrence, A., Acoustics in Buildings, Au8tralian BuildfugBcienee Series l, p 70,
1962.
D-25 Kosten, C. W. and van Os., G. J., "Community Reaction Criteria for External
Noises," National Physical Laboratory Symposium No. 12, London, H.M.S.O.
1962,
o.;38.
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D-26 ASHRAE; Guide and Data Book, Systems and Equipment, American Society of
Heating, Refrigerating and Air Conditioning Engineers, p 379, 1967 .
. D-27 Denisov;K I., "New Health Norms on Noise", Institut Gigiyeny Truda i Profza-
bo1evaniy AMN SSSR, Moscow, v. 14, no. 5:47, 1970.
D-28 Kryter, K., The Effects of Noise on Man, Academic Press, p 459, 1970.
D-29 "Noises in Tokyo", Report on the Tokyo Conference on Environmental Protection,
November 8-11, 1971.
D-30 "Sanitary Norms for Permissible Noise in .Living Quarters and Public Buildings and ...
in Residential Construction Areas," Main Santtary..E.pidemioldgical Adrninlstration;
USSR,:l97L
. .. . D-31 Beranek, L., Noise and .Vibration Control, p 585, McGraw-Hill, 1971.
· . ·, D-32 Doelle, I.·t ..g.~~iroriment~'4-~U.sti~s: .. p 186, ~fcGraw-Hill; ~1972. '. : .. ~
. · .. D-33 · Woods, R.I., "Noise·ControU,nMechanical Sex:vices/' Published jointly by Sound . . . . . . . . -. ..
Attenuators Ltd and Sound Research Laboratories Ltd, 1972.
D-34 Rettinger, M .. Acoustic Design and Noise Control, New York: p 158, Chemical
Pub!. Co~, Inc •• 1973:~ · . · , . . ··· ·-. · ·· ...
:': ..... ·.. ··~ ..
D-35 · Sweden Nati~nalBoar.d of Urban Planning, Samhallsplannering och Vagtraflkbuller, StockhOk:·.· :1971. . .· .. · ....... -_ .. · · · · .... · .... · ·-·· · .·
. ':·:··
D-36 Schweizerischer lngenieur-und Architekten-Verein, Empfehlung· fuer Schallschutz
" irn Wohnnungsbau, SIA.No. 18 t, Zuerich, 1970 ...
D-37 The Czech Miltistry of Heaith; Rl~htlinien fuer Gesundheitsschutz gegen unguenstige
Wirkting von Laerrn; Vorschriften der Hygiene, Band 28; 1967, Prague:. Staatsverlag ·
fuer Medizinische Literatur 1967.
D-38
D-39
. . .·
Der Bundesffiinister·des Iiinen, liiventar der in der BundesiepublikDeutschland ·
geltenden oder gep1anten · Recht&.undVerwalturigsvorschriften ueber die I:.aermbe,;.
kaempfung; Bonn Aprif ~0, 1973. . .
_., ... ·
"Impact Characterization ofNoise Includinglinplications of Identifying and
Achieving Levels ofCumclativeNoise Exposure.'~ EPA Document NTID.73A,
July 27, 1973. . . . .•. .
D-39
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A ndixE ·.:,'>:;·.· ·~· .•. ppe . .·:: ...
GENERAL EFFECTS OF NOISE NOT DIRECTLY USED IN IDENTIFYING LEVELS
OF NOISE REQUISITE TO PROTE(;f PUBLIC HEALm AND WELFARE
.··.· .. '
.,.•···;·"·
.·'·"'·
.,
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:•· .
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Appendix E
GENERAL EFFECfS OF NOISE NOT DIRECfL Y USED IN IDENTIFYING LEVELS
OF NOISE REQUISITE TO PROTECf PUBLIC HEALTH AND WELFARE
There are a multitude of adverse effects that can be caused by noise which may, both
directly or indirectly, affect public. health and welfare. However, there are only three
categories of adverse relationships in which the cause/effect relationships are adequately
known and can be justifiably used to identify levels of environmental noise for protection
of public health and· welfare. These are: (1) the effect of noise on hearing, (2) the effect
of noise. on the general mental state as ev,idenced by annoyance, and (3)the interference .
of noise: with.specific activities. These three categories of effects, discussed in detail in
Appendices C and D, will serve as the miin basis for identifying the levels in Section 3 of··
this document.
. . . . . .
Since a causal link be~ween. community noise and. extra,-auditory disease has not been.
established, this document proceeds on the assumption that protection against noise-induced
hearing loss issufficient for protection against extra-auditory effects. However, the gener-.
atiori of most stresNehited disor(iersJs somewhat'longet t~an that requir~d for noise-irid uced
hearing loss, and this time interval may have clouded a causal association. Noise of lesser
amplitude than that ti"a9ition~y identified for the protection of hearing causes regular
and dependable physiological responses in humans. Similar noise-induced physiological
changes in sensitive animals regularly-leads to thedeve~()pment. of stress.;related disease.
The implications ofgeneralizing from these animal studies to ~umans.is not clear. With . .
the availability of new informati6n concerning the role ofnoise.as.a stressor in the patho~ ·
· genesis of stress-related disease, the levelsidentified in this document may req.uire further
review.
· Inthe· meantiliie, the question that is invar.ia:bly asked is, "What is the significance of
omitting ail-other physiologiCal: effects?'' · · . ..
In answertd thiS question, most ·experts-agree tiiai, at present, there i~ insufficient.
· knowledge of the etfect-ofnoise on health, except-for: noise~induced hearing loss, (defining
. health in the ·more restricted: sense; :li.S, the:ab$ence· of disease).. In a recent review· of this
. subjectEi:1 jt was c~ncluded ~t; ~~if. noise control sufficienuo protect.persons-from ear' .
damage andhearlngloss were instituted,.then.it is hlghly.unlik'ely that the noises of lower·
.level andduratiotiresultiilg fro~:thiS:effOtt coul<fditectiyindtice non-auditory disease.''
Therefore, inthis-do<:ument,.hearing loss will be considered· the·controllingeffect.
. . ~ .-
.: ' ...
. ··.-·-··
:'•· .. ·.·' ... :
. . . ~ .. ·
_., .. _ ... ,-.. .·: ··.·,: ··;-;; '.<c'"·'
. ·-·t· .·. .'l·
. ·. . .
This is not to say that there are ho fud:leatiom. to an;~ concern bt. the· area. tiih~n~ •.
. . auditory effects~ but substantial-further research ·oriJ.hese'. effeCts or:n~;on·,~th· would •. . . :· .. ;• .
be required to alter ~he abovestat~ment~ Such.~c,h.;sh~:iu4:befostei~-,:-and·~·result'$ .. . ·:::i~::.::::n~~ n::~~ts~~:: -~~~.~~f. ~j.~d-~ce. fdi~:~· ~"~.,~~-~y'S-:~~~~·~Y~~-~:;:.'.·.":·c:~· ... : _.·.
...... :. . ;~ -~ .......... _,~ ... '·,.'.. . .. :• :::.:·.:.:·: ..).·;:·.:· .. ·::-
··· · ·· Although noise .can· affect people. indirectly by.<listurbing•the generahnvii"onment in :. •· • -· · ·• · . . . . . . .. . . . . . . .
which they live~ the· noise levels requited to produce sigruficant non-auditory :Physiologieal·
.effects are •normally niuch higher· than the 1evelneqwh~d· to protect the:publlc health:and ::.,/ .·:
welfare from ~dverse eff~cts on hearing Or interference\vith.activities:. ... . . . . ., · ·
... ·.:··
·· •However., forsp~cial conditions, certaiil effects. which h~ve·not bee~.ditectl:Y.i.ltilized
. in identifying· thelevels.in: ·this·docum~nt, Should be' examined~.··. For thiS putpo~;: bertam
of the summary paragraphs of the EPA criteria dqcument·' .. Public:Heaith:andWelfate ·
. C:titeria for. Noise''E:l . al-e. included _m this apPendix~ C:aution·must · b~-~~e.tC.~~ when .
using such information since, in many .cases~_th~e is no way tor~I.ate theexacte~posure
lev.el to the· eff~ct m·: question~ . .;···.. ~: .. · .. ··~ •.' ... :·' .. ·
EFFECTS OF NOISE ON HUMANS. ;= ..
Performance and Work Efficiency
... · .... ,.·.·
Cori.tirtuous noise levels above 90 elBA appeatto· have potentially d~trinierltal effects ·
on human performance-, especially on what have: been described a:s noise-sensitive-tasks
s~cll as vigilance tasks, information-gathenng and ~}"tiCal processes~ >EffeCts of ~oise
on routine-type tasks appear to be ·much·less ini:l;.ortant, although cumulative· degrading
.effects·have.beert demonstrated· bY rese~chm~·····Noise levels ofl~ss th·an:90·dBA_:.-can:·:be·;. · ..
,":' ...
. . disr?ptive, ·especially if ~hey have predominantly: ,high fi'equency::coinpon~If:U;· are·:m.tex·/ '::::·· .. ·:··
. . . mittent, unexpected, or uncontrollable .. The· alllC)unt of disrtiption is highlY'dependent onJ .
···· .. ·· . • •· 'the.typeoftask
• The state of the human·organism.
• The state of morale and motivation;
Noise does not usually influence the overall rate of work, but high levels of noise• may
increase the variability of the work rate. There may be "noise pauses" or gaps in response,
sometimes followed by compensating increases in work rate. Noise is more likely to. reduce
the accuracy of work than to reduce the total quantity of\vork. Complex or demanding
tasks are more likely to be adversely affected than are simple tasks. Since laboratory studies
represent idealized situations, there is a pressing need for field studies in real·:tife conditions.
E-2
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Although these possibly adverse effects were not used in identifying the noise levels
in this document, employers or educational authorities should consider their influence
since it might provide additional motivation to achieve the values seen in Table 0-10 of
Appendix D.
Effects of Noise on the Autonomic Nervous System and Other Non-Auditory
Physiological Effects
Noise can elicit many different physiological responses. However, no clear evidence
e~ists to indicate that the continued activation of these responses leads to irreversible.
changes and permanent health problems. Sound of sufficient intensity .can cause pain to
.. . .. . ... the auditory system, however, such intense exposures are rarely encountered in the non-
. ~occupationat enVironment. Noise cmulso affect one?s equilibrium, but the scarce data
available fudicates that theintensities required:to.do so must be quite high, similar to the
intensities that produce pain.
Noise-induced .orienting reflexes serve to locate the source of a sudden ·sound and, iri
combination with the stattle reflex, prepare the individual to take appropriate action in
die event ofdanger •. Apart frOm possibly mcr~sing the charice of an accident in some
situations, there are no clear indications that the effects are harmful since these effects are
of short duration and do not cause long-:-term physiological changes .
. ....
. Noise can. definitely interfere with·sleep, however; relating,noise-exposure level to the
· quality of sleep is:difficu.It. Even noise of moderate levels can change the pattern of sleep;
but the significance of these changes is stilhn open question. · ·
Noise exposure may cause~ fatigue,.irrltabillty,.or insomnia in some individuals, but the
quantitative evidence inJhis x:egard is.alsO. llnclear •. No fl11Il relationships between noise. and
these factors can be estiiblls.hed: at this tinle; · · · . . . · .
Interaction of NoiSe and.Other Conditions or Influences
D~t~~iti~n,~l how varl~tis agerits or conditions interact with noise in producing
. a given effect·req~.three sep~te detenninations: ·the effect produced by the noise
.· 'alone; the effect produced by the other agent alone, and the effect produced by the .
combined action oftli~ agent and the noise; These results indicate whether the combi~ed
effect is indifferent; additive, syner:Pstic,. ot amelioratiVe .. . ~ ...... , .. : ...... -.. · . . . . . : . '
E-3
-··· .. :.
. ·.· .; .. :::.
.... -:·-.....
···.·· '·.·
.:. ~-,--~ ;: : ·.,. ·: ·. \:. . . . ·. -~ ; :.:·.
.. _. •;:
Chemical agents may have a·haxmfuLeffectwhen-combiriedwitli·noise; Ototp~ic
drugs that are known to. be damaging_t?:the·hearing.mechariis~.c~n,_P.:¢..':~UJ!ielf:t9.;Pr~UCe.· .. :
at least ai:t additive effect o.n hearing: when combined with noise; exP.o.sA~e. Ther~ ~r(! ·. ·.· .· .. · ...
instancesilfwhich··individuals-usillg-.medieation'tem:por.ari:}y'suff~~~;he~ifJOsi-V..it~tt-...
.• ex pos~Q. to ·noise, but:theie is .no de.fmitiV:~-data .on· the:·lntera~tio11 b{.o.tcjt.cixic;drii.gs·-'~ind'' ;.;;,· ~· :.. ·. · :.-·· ·
noise on humans. Evidenc~ linking heanng.·loss withithe 6~mhinatiori:O:f.ll.Oise·:andi~dus~ .
trial chemicals is also inconclUsive; · · · · : ,.-:. · · .. ~:·.:. . . '·. ,· '· ·.•'.
·• .. ·
. ..... , ..... ~ . : ~ . . · ... ' ; . -._
•-;!·' The· possibility of a sytie~gistie et:fect.exists. w.hen:riOise anct vibtatiwi.odciu: :together;···
. .·•·.·
Vibration. iS us~ly more ·potent th~ ~~ise in aff~cting phy~jological,.p~et.~s.~·There· · .· ..... .
· appears to be con~1lsus that'\iibration~:incr~ses·tb.~·eff.ect:qfri~ise o11 hearlng; but ~~ch. · · ·
increases are probably quite small, . . ... . · ·. , ·. ' ·.· · · ·. : :--~ : . . . .. · .. _.·,·; .. . ...... ..-.·....... .... ..
· Health diso-rders may interact with n,oise tQ .produce a helU'ing loss. Mineral and· ....
vitamin deficiencies are one examPle hut little rese~ch has-been~done on the eff~ct of such .. ·
· ·.deficiencies on susceptibility to ,noise. . A ·r~sonable hypothfsi~ is tliat 'illnes~ increases an
· individuars.susceptibility to th~ adverse effects:·o-f}~~i~; kow~~er, a~·:Witli:the:tiilier·hypQ-
theses; conclusive .e~idence is ~c.king. ·.· . .:.. . .. .. ' ._ ..
:: .. : .... --~.
' Noise.expOOire ctm be presumed-to··.cause gen~rlif8t~s~-:-by hselfqt:iiC~rihj~ction .. ·.
with other stressors •. :Neither the relationship be-tween noise··exp_<:>sur~:~~rstress n~:t:<the ...•.. ··
noise level or duration at which stress may appear have been resolved. . . . . . ·.
' . ;_.. : ·, .' ·. .
··· ...
Exposm:e to: moderate. il'lten~ties,of.~ise that are likely: to be found in· the -environ•
... , . ment may· affect the cardiov.asc.ular sy-stem-in v.~ous·ways, 'but no -<i:e:flriite pe.miall,ent
eff~cts on the circulatozy system have been demonstrated. Noise ofmOdeiat:ctintertsity
.. ,has been found to causevasoconstriction of'theperipheralblo.od·vessels-and:p.upillary .. ·
. dilation: There is· no evidenee· that these reactions to no1sy·.~hfuonments.:6a.n -read: ·to.~harm-· --: ,_
fu.l consequences over prolonged periods of noise: ex_po~~. ·However; s.pec1Jlati0.n. that . · .. ; , .... ·
. noi~e .might be a contributingfactor to circmatory diffi.culties,lUl.d heat, _cf.is~.se ~ not yet-::'·· ·
· supported by scientific data·.
.. . . . ~
·-:: _:.·, ..
EFFECTS OF NOISE ON WILDLIFE AND OTHER ANIMALS
Noise produces the same general types of effects on animals as it does on humans,
namely: hearing loss, masking of communications, behavioral; and non~auditory physio-
logical effects.
The most observable effects of noise on farm and wild animals seem to be behavioral.
Clearly, noise of sufficient intensity or noise of aversive character can disrupt normal
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patterns of animal existence. Exploratory behavior can be curtailed, avoidance behavior
can limit access to food and shelter, and breeding habits can be disrupted. Hearing loss and
the masking of auditory signals can further complicate an animal~s efforts to recognize its
young, detect and locate prey, and evade predators. Competition for food and space in an
"ecological niche" results in complex interrelationships and, hence, a complex balance.
Many laboratory studies have indicated temporary and permanent noise-induced thresh-
old shifts. However, damage-risk criteria for various species have not yet been developed.
Masking of auditory signals has been demonstrated by commercial jamming signals, which
are amplitude and frequency modulated ..
Physiolbgi~al effects of.noise·exposure, such as changes in blood pressure and chemis-
.. ·' · ·· .. · · try, hormonal balan~ and reproductivity have been d.emonstrated in -laboratocy ariimals
and, to some extent, in farm animal$~ But these effects are understandably difficult to
.. ' assess in wildlife, Also, the. amount of physiological and behavioral adaptation that occurs
.. in, response to. noise. stimuli is a!) yet unknown. ·
··:··
Considerable· research needs to ·'be accomplished before more definitiVe criteria can be·
developed. The basic needs are~· .. · ·· ·
,._··::.-._:.. · .... ··:.::•
e More thorough investigations to determine the point at which various species
incur hearing loss. .
. . . . . . . . . ..
. '
• . Studies. to determine ,the ·effects· on animals·Ofllow-level; chronic.nchse
exposures.
• Comprehensive studies on the effects on animals in their natural habitats.
Such variables as. the.extent of aversive reactions, physiological changes,
and predator-prey relationships should be exaznined.
Until more information exists~ judgments ·otenvii:6riirientai impact ~ust be based on the
existing information, however incomplete. The most simple approach is to assume that
animals wiil be·.at:least p~rtia!Jy protected:'by.application of maximum levels identified
for human exposure. ·· .....
. -~
EFFECI' OF. NOISE ON STRUCTURES.· ...
Airborne sound normally encountered:inreallife-doesnot usually carry sUfficient
energy to cause.damage to most structures.· The major exceptions to this are sonic booms
produced·by.supersonic ~ircraft; low frequency. sound produced by rocket engines and some
construction equipment, and scmiC fatigue: .. . . . . .
E-5
.·.· ..
':'·:.·· ...... .
........
.. ~ .... · , .; .....
From an· environmental point ofview; the most significant effects are· those ca'U~d:·by
S<>nic booms on the· secondary components· of structures. ,Thes-e eff'ects·mclude:thebreakmg. ·
of windows. and· cracking of plaster .. Effects suCh as t4ese ~ve.led tp· ~ speculatiort that
. :t:a~~~s~;~~b:::.~~==~=~~~~l~i'i~~~:hdi;~~~!P!t~~f-j~. · ' ..
.·adverse effects <>n public health and· welfare are·lo~ .~6tigh.tct·proteet ~iafttst= damage · .
to·structures.,..... ...... ,,:· ........ , ··::.,.-, .. : ... ,,.:.····':'"'''···· .,.,;,·, ....... .
·:' . .. ' ....
• ,,•I,• I ''•
,;·.,
· ... ._ .. ;
· .. ' ... ·. ;.;.
. : .. ·~;, .. ·:'-·:.·:··: .. ····" · .. ··.· --~ .. ,. ·····
;:,., .. :··
·.' '.'·
..... ·. ... · .... : ~ ..... · ... :
_ .. :
' . . ~. ·-
. , .. --.~:; ..... . . .... .·• . :--·~.; ~--;· . . . ,. . . . . : ·: ,' ·-~ ...
. ... ,_'
. ~--:"''
'·:· ......
·.·:·" ·.·
::-· .. _. ...... · ........ _ .... ·; .. ··
. . ~-·
.--;• .. ;•:: .c·;-::';~:;~.,. ;, '
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-~··· -~ ...
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~ . . .
REFERENCES FOR APPENDIX E
E-1. "Effect of Noise on People," Environmental Protection Agency, NTID 300.7,
December 1971.
E-2. "Public Health and Welfare Criteria for Noise," Environmental Protection Agency,
550/9-73-002, July 27, 1973.
.-·-·
... ·>;
..... '· ·. '• -... ,_; ···~··· ·. '
._.· ~-. :·.· • .... -.. _.::
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.... ·· ... -..-.·.
E-7
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_. -.: .-...
. . ···. .. . ' •·. -~ . -:.··· .. . ~ .-.-;.,·· . . ' .· .
.. ,·, ·. ~-..
EP Ns RESPONSii3ILITY TO IDENTIFY SAFE LEVELS FOR
OCCUPATIONAL NOISE EXPOSURE
.":'. ·.
. ~ ~-.' .....
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AppendixF
EPA'sRESPONSIDILITY TO IDENTIFY SAFE LEVELS FOR
OCCUPATIONAL NOISE EXPOSURE
Although the workplace is a vital component of the human environment, the Environ-
mental Protection Agency does not have jurisdiction over most occupational health and
safety matters. These matters have traditionally been the responsibility of the Departments
of Labor and Health, Education and Welfare. Section 6(b)(S) of the Occupational Safety
and Health Act of 1972 specifies that the Secretary of Labor; " ... in promulgating stand-
ards dealing with toxic materials or harmful physical agents .... , shall set the standard which
most adequately assures, to the extent feasible, on the basis of the best available evidence,
that no employee will suffer material impairment of health or functional capacity even if
· such employee has regular exposure to the hazard dealt with by such standard for the per· • · ·
. iod of his working life ... In addition to the attainment of the highest degree of health ·
and safety protectionfor the employee, other considerations shall be the latest available
scientific data in the field, the feasibility of the .standards, and experience gamed under · · ·.
this and other health and safety laws."
in c~n~t; ·section 5(~)(2J6ft~ ·Noise Control Act·ort972 diiects.EPA'sAdrtlinis-·
trator to "publish information on the levels of environmental noise, the attainment and
maintenance of which. in defmed areas Under various conditions are r~quisite to protecting
the public health and w~lfare With an adequate margin of safety." . .
."··.· ... ' The·~~rds .. ·public health ~dwelfare~ app~ar~ a number: of pla~es in the Noise
Control Act, and have a broader reference.than.those c;lefurlngjurisdiction in the Occupa-
tional Safety and Health Act, namely, the entire American public at all times rather than
the American worker during his workday. ·ln addition, the requirement of an ·~adequate
margin ofsa.fety",doesnot appear in.the Occupational Safety and Health Act, which
.. instead tises the phrase, "no·employee·will.suffer .material impairm~nt of health or func-
. tional c~pacity';" ·These distinctions indicate that EPA's duty to identify levels fbr exp6suie
to noise is broader in scope and more stringent that OSHA~s· duty to protect in the occupa~ · .· ··
tiona! aiea:; Fmtliermore, the·intent.ofthis docuni'entiS to identify safe levels· for a variety ·
· . of settings~ whereaS. the responsibility of HEW is to develop occupational. exposure criteria
· and that of the Depart~ent of Labor is to promulgate and enforce standards. · In·the writing• ·
of such standardsi. 't'he'Labor.Departnieiit'·must.take 'feasibility into account, a consideration , :. · ·
omitted in the writing of this document. · .. :
EPA's responsibility to identify levels of exposure t ;') noise .. in defmed areas under
various conditions" necessarily includes an .identification of exposure. levels in the workplace
F-1-tU
. . · ... ··,·.-.·
-··
' . ~ ..
'•': ..
:;:.'·".
in order· to satiSfy the irttfmt ofth:elaw·to oonsidet·_totalhinnlll'l expoSure·:to·no.jse,: Work-
ing hours ru:e an inseparable piut ofthe .. inQividuai•s 24-hour-•day;:.tl"t:i~iliey rtitist be c6ri-:-·· ·:· ·· ··
sidered in order .to· evaluate the:can~Jl~j9rts' of nonoccupatia:nal:exp6,hlite'~~:rus·dallyand ' ..
lifetime· dose~ For this reason, it ·is -of. utmost importance that-.th~ leveis·'sPecifled· fot occu-· . . . . . ·. : .·: . . .;. . . . . . . . .· . . . . . . .·. : . . .. : . . . . . . . ~. . .
pational and non .. o.ccupational·noise '.be' compatible~.·,·,: '· ·. · · ·• · ·· ' · · -: ·
:_.; ... • ,· '.• .. ,.· .·.·.·····
•'.\·::·.": ., . <·: .. :.·. '; •. .. :.-·.: -~ · .. : .. '.; . ::·/ ,• ~-:-: , . .' . ·•·· ..... .
......
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. · .. .. ·.· . ·:.•." .
... ,:_. .. . ·· ... ·_:. ..·.:·--."·--· ·:. ' .. : ~ . .-.:· :· ·, · ......... _. .. ; .. ···-~
·· ..... . :··.:~· .... : .. . .'
· .. ··.-:
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. "'•'·.;·;_, ~·: ~. ' .....
'··· .. ··:···
·:·_;:··.:
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• 4 •• ~·. : .' • ••• :
.· .·. ·--.. ..... · .... •:.·. . .. _;
,; :-. ·. ~-. ... ~-· ..
:-:.::. ,.;.· .. ·:; .. : .. :~· ... , .. : .
· .. · .. : .... _ ... •. ~ .... · ... . . .-~ ... .. ·.:
.·,· :• .r .
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[-· . ··Appendix G ·
..
. · IMPULSE NOISE AND SOME OTHER SPECIAL NOISES
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Appendix G
IMPULSE NOISE AND SOME OTHER SPECIAL NOISES
IMPULSE NOISE
Impulse noise is defmed in various ways G-1, G-1, G-H but generally means a discrete noise
(or a series of such noises) of short duration (less than a second), in which ~he sound pres-
sure level rises very rapidly (less than 500 ms, sometimes less than 1 ms) to a high peak
level before decaying below the level of background noise. The decay is frequently oscil~
latory, because of sound reflections and reverberation (ringing) in which case the spectrum
of the oscillation may ;Uso be important in determiningthe hazard to hearing. Some
.authors distinguish reverberahtimpulsenoise as "'impact'' noise (typically ptoduced·by '
metal to metal impact as in industrial·fo:rging), to distinguish it from simple·oligophasic
·impulses (typified by a gunshot in the open.air}. G-l
. The peak sound pressure level (SPL) is. an important but not the ~ole parameter
·· d~termining hazard •. Some typical valuesf().r .disturbing'orfulzardous impufse.noisesare
given in Tab-le Gd~ .· ... · ·
NOTE: Peak SPL for impulses cannot be properly measured with a standard sound level
meter, which is a time-averaging: device~ Oscillographic techniques must be used.
Table G-1,
SOME TYPICAL VALUES OF PEAK SPL FOR IMPULSE NOISE
(in dB re. 20 micropascals)'
SPL
190+
160-180·
140-170 .
125:..160 •.
120::~140
110.13(}--
.EXAMPLE
Within bl,ast zone of exploding bomb . . •. •',
Wit4in crew area of.heavy artillery .Piece or naval gun when
shooting ·
At shooter's ear when firing hand gun
At child's ear when detonating toy eap or fir~cracker
Metal.. to metal impacts in many industrial processes
(e.g.;· drol>'"forging; metal-beating}
On construction site during pile-driving
G-1-·a_/
. '-~
Effects of Impulse Noise on People
\
Cochlear Damageand He~gLoss,·
. ::··'·"·
;·_::
.......
. ~-' "', ~-· ·;
,_: ..
.~: , .
,· .. '.' .. .. .... ;'
':·-.·· :-·.··,: .
• Impulse noise can· produce tempol'aiY-.(TTS).aild:perlT1cl.nen·t•threshold;shitt.(PT~J; .. . . .
The pattern essential.ly resembles th~t pl'()qu.ced by,~,~n~!ll:19:~s;noise b-:u.t'jpay:,involve · ....
somewhat higher frequency losses (m.axnnal at 4• to 6ldfz). ~d .recovery Jroril;iritpUls~ . ~·
NIPTS can be more v~iable.<>-9 • A blow to the hea~ eari ba~~ a:siiniliir:.effect.• Ts,s·:(~, .··
by infe~ence;.PtS}ili man dep~ds..on:many·facto~;the;.ll1Qre bnportant:~f~w·hichiare ·
reviewed in. more:detaii later~ lmpulse .. ppj.se~ (like' co.ntintious·naise) can··atsQ;·resho:wn•to': · ·
. produce pathol~gicichanges in. the inne~ ear.(coc~lrif.Puunmals, p_otablYdeskucti~n. ··· .. "·· .·
and degcmeration of the haircells• of the·hearlrig oriari·;··an:cr atropJii~ cttanges.lli'telated ..... .
. structures;· A quantitatiVe relatiOJ:lshlP between the ainoJ.Intcdfvistl;le·'darii'agctothe ·•' : • · ....
. .... .. . ·.co.chlea and the amount of NIPTS ha8 ·not yet been· clearlY esta&lished~ c;.2i'G;:4~.<>-s. :':' ·
. . .. · . . ' . ' · .. ; . ." ' . . . ·. ,._, ' .. · .. ·.' .. :: ·. ·:, '~ :··, .. ·.-· ." . ' . . . . .. _., .. ·: ~: ...... .
. .. :.
. -__ ,,_ :-:·-.. _ •. :.'. -:-.-··::• .'~· .. · ... ·--~.;: · .....
:.-·.•.<· ·.:.·.""· .. .:-.
. . .. ··· . '-~-: ; .,c,:"< :: : .
·.··. -··-::':···_.;,
':: ·---~ ':•!.. . · Other· Pathological Effects· · . . :; .:.~ ~; ... _;_-_. . .;--"·
••':•:: -·-:·•·'· . . . -. ···-~·-.
Exposilre to bl~st or to sustain~'~irepeated·firi{;ul~~~\tithofne oy~ipt~$u~iri the·· ., :. ·.
· .. range· of·l40 to.l5.0·dB:(239'to~7l8 paSCids)·or hi·girer can·.~u~e··geriera~~ciiS.t~~baneeot ...... ·· ·
damage to. the.b.ody apart from the. ear~ This is noxmaJly. a. problem for militaiy.'.:perse~nel · · .. .
at war (e.g., artillerymen nrmg neld guns), arid n·eed not be consirier~d. further here. 'fran~ .. ···
sient over-pressures of considerable magnitude can be experienced dit~ to. sonic boom but ·
are unlikely to be hazardous to the ear. · · · ...
··-···: .. :·
Startle and Awakening· -.:.···
-:.·: ''·. ':.: ..... ._,:;·:. ....-.. ·-,:,. . . '. ~ ... -....
Impulsive noises which are novel; unheralded, 6runexpectedly loud: .. ca;n stirtk.t)eopl:e. ·
and animals. Even· v~ry mild impulsive noises can aw.~ensle~pers. In S9J?:!e: CU.:~s~ahces> ..
(e.g., ·when a person is handling delicate or· dangerous objects or rriateriills)~.·Staitle:,can·be
hazardous~ Because startle and alerting.tesponses depend very largely upo·n individual
... circumstances and psychological factors unrelated to. the· intensity of the sound;-it ~s diffl•
cult to make any generalization about acceptable values ·of SPLin this con~ecti~n; ··A high.
degree of behavioral habituation, even to intense ·impulse noises such as· gunfire; is ·normally ··
seen in animals and' humans wheri. the exposure is repeated,. provided that the cliat:acter of.
· the stimulus is not changed.
.: -.:.•
G-2
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iParameters of Impulse Noise Exposure
l.mpulse noise is characterized completely by the waveform and spectrum. Various
summary parameters are also useful in characterizing an impulsive noise, these include:
1. Peak SPL (in dB re 20 micropascals)
2. Effective duration (in milliseconds or microseconds)
3. Rise time
ln addition; the,following are important for predicting the effects of .the impulse on people:·
4. Number ofrepeatedimpulses ina daily or other cumulative ex,posure
;
I.
5. Intervals or average interval be. tween repeated impulses (or rate of impulse
. ,occw:-rence)·
. -· .. ~:-... ·. · ... --~-.. .
6: ·.Individual s\isceptibility to inner· ear damage
'··; • ,-' ., :;·,·, .. <c:-:·-:··-.· .:; . •• -~; )_-· .. _..:-•· ." ~'··· '.,
. 7. .· Orientation O-r the ear \vith respect to the noise
8.· · Prece~~g·or Simult~heous exposure to continuous~oise at TIS-producing
. levels
.. . : . . . .. -~ .· . ·'
9~ Action ofacousticr~fl~~.:·ifeiicited
,10. Audiometri-c frequency
Impulse NoiSe Expo8ure Critena and Limits ·
._-.-~ .
· Hearing Damage and Criteria for !mpulse Nois~
. It is ob'Viotis from the above lists that limiting impulse. noise exposure for hearing con"
s~r.vation is not an ea:sy matter. ExistiDg guidance. in this matter in some spheres.is seri-
ously inadequate ormisleading.G-3. Forinstance; the.Occupational Safety and Health Act ·
prescribesa.limitinglevel of 140·dB SPL for industrial impulse noise, with no allowance for
. any other parameter. . . ··. . . .
·· .... ··
G-3
.,··
... -
... :.:
,.
~-..
'i· ,.···.
In 1968; Working Group 57·-ofCHABA prepare<h-<iarttage risk ~riterloif'fdrgunflie. ··
noise, based essentially on the w:otk of Coles et. at~-'*which. indude.d·pr.Ocedures to allow
for repetitiOn of i~pulses and some of the oth~r parameters l.iSt~d ab0ve.9~i .·Some modi-
fication has recently been proposed by Coles and'·Rice.,:G-7• -The CHAB:Apropos'alwas
intended to protect 95% of'~he exposed:popl,ilation~· ... ,, ·. · · · · · ·
-...... · :\:::..~ :. ·· ....... ""·.·····.·
· .... .· .··.· --:·.' · ... ; .. ··'"
·:··::::: .. '.· .. : . ..:.·
··· .. ·.:.
·.· ... Guideffues for Evaluating Hazard ·from hnp~ NoiSe EXposure . . . : . . . . : ·.. . . ... : ....... · .. ·
Peak Level · .. · .. '
:···:•.
The growth of TIS at 4 kHz with-increase in peak level above po. ciB·SPL<:>firtlpulses · ·· ·
. (clicks} presf?nte4 at a steady rate has.b.e~n demon5trated.byWardet. a/:~8 Based O:nrrs. ·.· ...•. -
data from rifle shooters; Klyter.and Garinthero;1a estimated permanenthe:aring:lev:els. · .·
expected to result from daily exp()sur~ to a noJ:llinallOO roun~ .of title Shr~>oting noise .u( ..
· · ··· -· 8elected p~rceritiles; Thclr.dataate teproduced iii Table G2 b~low;.shoWing the increasing
hazard with increasing peak level and vv-ith increasing: audiometri~ frequency U.P to-. 6000
Hz. · ..
''• ·. '~ . . .
. : CHABA's 1968 Damage.=Risk ·Criteria (D RC)c;.;1 ·r.ecom:inended •liriilts to peak level as i · · · · · .. · ·
function of impulse duration f~r a nominal exposure of 100 impulses per day at normal
incidence (discussed below and shown in Figure G-1). These limits were intended to pro-
tect 95% of the people according to an implied criterion of NIPTS not exceedirig 20 dB at
3kHz or above, ~ter 20yrs. lf90%of the people were to be protected·toacriter;ion of
. NIPTS not exceeding 5 dB at 4 kHz, it would be ne.cessary to lower the CHABAlimits by.
12 dB ( 15 dB reduction to mee_t the Ill:OJ:'e stringent priterion,_ assurriing an. apprpx.imately
decible to decibelrelationship in the· range of interest [see T~ble G-2],l¢SS3 dB el~vation .
to apply the limit-to the 90th percentile). This modified•CHABAlimit:is·~shown·ipFigui.e.
~ G-l by hatched lines._ . ·· .. = • •.· .. ; .•.• • ,
,. '· ·.: ,.;· '-·
Duration of ImpulSe
Hazard increases with the effective duration of impulses. G-lo Impulse duration is
defmed according to the type of impulse (A, simple peak, orB, oscillatory decay}; G-1, G-6
and CHABA has recommended separate limits for A-and B-durations (Figure G-1 }. For
effective durations much above 1 ms, a more stringent limit should be applied· to reverberant
oscillations (e.g., metallic impacts in industry or gunShots in a reverberant indoor·range) ·.•
than to simple A-type impulses (e.g., gunshots in the open}. When the type of impulse
cannot be determined, it is conservative to assume the &-duration;
G-4
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Table G-2
ESTIMATED EXPECTED PERMANENT HEARING LEVEL (IN DB RE ASA:1951)
IN SELECTED PERCENTILES OF THE MOST SENSITIVE EARS
FOLLOWING NOMINAL DAILY EXPOSURE TO RIFLE NOISE
. (DURING TYPICAL MILITARY SERVICE),
NAMELY, 100 ROUNDS AT ABOUT 5 SECOND INTERVALSG-18
Peak
SPL*
(dB)
170: ..
165
..
·.1.60
··--·, tso
.· 140
. .
Percentile
Exceeding HL ... '····.·.
10
.. 25
so .. : .. ~'c:'_
·'to ···''·
25.
so · ... ··· :.:.,·., ·<: ,· .. ·>
JO
... 25·
... ;_-~·:so·.-·:-·.;··-
.·-·-
. .-.. :,:-to
·.:. 25· .. ,
.. ·· .. _._,.
so ,· ...
. . -· -~ --: . . . . . . .-:. . .
10
25
·so·
1000
· ... ~
15 . ····a
~-16
9
0
.. IS. ··
.!
0
····.;.
-"·10::
3 .•... 0
. 0·
··0
... 0.
Audiometric Test Frequency (Hz)
2000 3000 4000 6000
35 70 85 90
25
..
55 65 .. 70
•.
10 35 45 50
~ ...
20 .. 62 60 '67
10 32 45 52
0 12 25 47
-·-·:',·,_ .
16 25 45 .·60
8 18 . 35 45
15 25
..
0 0 ..
..
: . ·15. 1.5 35 so.·
...
4 8 25' •.
40
'(J 0 1'0' '20
5 10 .. . 30 45
2 2 18 30
0 0 5 ·to
. CHAB,AG-i ,.L968,VIame.d..th~t the:l52 and 138.(JB.plateaax are only. "gross estimates''· ..
·simi1ar.remarksapply'to the:modifiedCHABA.limit.here.proposed,.in.which.thecorres-
ponding plateaux are 140 and l26.dB$PL. '. . · · .... · . . ...
·:--·· ... · ... -~ -.
.... · ..
G-5
:._..
' ~ . . . . ... . ... .:
·. • ..
.;.J 145
.. -· ... '• laJ' ·.·· >·" ·w···: .
..J
laJ a: ;:,·
.. •-: .. ·· "• .• ..
•:,:·
.. ·.··.•.
......
··.: .• :, "• :;· • • :~ I' • • • '
-·.;. ..
. . : .. ' . . .. ~ .
. ~ 135.
~-···
·'.
',.,.
·.:., ..
a..
:.:: 13'0·.
c:(.
~-·· 125
. . . . . . . . . . . " .•:. ~ ...
·· ....
I. ! . ;. I... !
.05 . .I .2
. DURATION IN M! EC
·._· ... ·· ·• ;·
h·.· ~ : ...
'' .,·
Figure G-1. The 1968 CHABA Got Damage.:Risk Criterion for Impulse N~ise
Exposure (solid lines) and a Proposed Modification (hatched
lines). Peak S<;>und Pressure Level is-Expressed as a FunCtion·
of A~ or ~Duration in the Range -iS MicrosecQnd.s to.J:.
-Rise Time' ...
' · · .~econcL 0.1 .. • . · · ·
. ·.· ··•.·,·. ,. ·;.•
..... :-.,·
·· ...
.....
··.
.·· .
.. · .. · ..
..: _., ...
. ' .. ' . .: . . . ---~ . : ' . . ..... ·;. . .. ;. :'./:. : ___ ; ;--~ :;·' .......
.... , . . . ntis paramet~ ~usually correlated closely with peak presiure~ Pi"esent evidei1ce as to
. .its effec(on heiuing risk is insufficient for allowance to_ be made for it in-damage risk . ···. ·-. . . .;··. . ... · . . ..
. " -.. c;riteria. .
• ... ···
Spe~truin (Or Waveform)·
Impulses with largely high frequency spectral components (e.g., reverberant gunshots)
···are generally more hazardous· to the hearing mechanism than predominantly, Iow;.;frequency · · · ·
.. impulses (e.g., distance-degraded blast waves; sonic booms) of the same· peak SPL. Howevf''",
comparative data are as yet too scanty to serve as the basis of differential damage risk
criteria.
G-6
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Number of Repeated Impulses
TIS (and, by inference, NIPTS) grows linearly with the number of impulses in a series,
or linearly with time when the rate of impulses is constant. G-s CHABA G-1 recommended
an allowance of -5 dB for every tenfold increase in number of impulses in a daily exposure
(Figure G-2). Recently, Coles and RiceG-7 have contended that this rule is underprotective
for large numbers {N) of impulses and have recommended a modification (see Figure G-2\
In 1973, McRobert and Ward G-3 questioned this modification, maintaining that it is
probably grossly overprotective for N> 1000, and commented also on the CHABA rule in
the light of recent experiments. Figure G-2 reproduces a comparison by McRobert and
Ward·of the CHABA rule with Coles. and RiceG-7 and an "equal-energy" rule (10 dB weight-
ing for each tenfold increase inN) originating at N = ·1 00.
. Gi.
"0
.. · . ....... .. . :. .
.-25
··· ..
. .. ·: ..... ··.··-:·
\ \""'-.. · \ .
. \', ""· '\ .. · ""-
\·
' \
\.
\
.. ·:· ...•.. ·· .:-.\ >:: .. "
COLES& RICE . '
. ?. 11971·) ~··
.. ·· ... .... ..
' '
NUMBER 'OF iMPULSES
. Figure' ci2~ t~~parlsori'ofCllABAWeightfu~(Re: Zero at·~~~ iOOimpUises .· .· . · ....
.per Day)· for NUmber (N) of Impulses in Daily Exposure G-1. with the.·
· Proposed Modification by· Coles and Rice (;-7. and an "Equal ..
Energy" Rule. After McRoberts and Ward. G-3
G-7
··.·. : .". ··. ,":; ·.·-.. .: .. :• .... ·.":' .. v"
· .. ··.
. '.•
··-.:,.
-,:_:
All in all, an "equal'-energy'' rUie appears to fit the existing: data tolefabfy.wcll-~nd is.
easy to apply iD. prlictice, but if may underestimate ·ffie hazard. for valu~ ·or:~ ;suhstantia:lly .
·~ ·. '
· less than 100 (isOlated•impulses); · ··-· · : . ···· · -~' >. · .... ,. -. · · ·
·-.. ,_·.:, ..... ·: :· . .-.-...... .
. • •• h' . .· .. ~ . , ... , .. ·
·· ... ' ·.···· ... · ·_; ...
. . Watd..-et. a/G-!l$howed that,. when_eq:ual impu~es·:OC~;U;r-:at·morethan'l/s;.TIS·-
. · develop~~~---~s --~~9.~er .than--~~~~ ~-, ~y~ge interval:i$ ~-.t;te:.rang~' .:J-.:t:o;-" .. 9.-~;;preS~m:~~lY -: :~., <-·-..
. because the acoustic reflex is nlaintained.. When the interv:ill is lti.J.lg (.Iange: 9· • jo::seconds)., .
. TTS again.developsmore.slowly; probably because·the·intenial allow.sSO.mereeovezy. A .·
~-. conservative rule would be to apply-a 5 .dB penalty _when· :the average· iittptili,e·.~tervaUil~s ' .
between 1 and 10 seconds; such an futerval may be typical of such activities ~-range
· · ~liootingin groups,.heavy hammering i.J?.:ind'ilstry, P~.Pil~V:~g;.': ~-. .. . . ·
··~ -.~':".-. .;·: •:··· .. _. • ... · .: ; · .. ·.
. . . . . ' ; . : .;·: ... -~ . ·:. .
Individual Susceptibility to Inner Ear. ~ge. · ·
·.·.:.:}.:;: .. -·. -:··.'·
··.:.: ·, . -
... ·. •. ~-·._.::·-.. ·'·.
·The distribution of individual-susceptibility to Nms and·: NIPTS iil the J>optilation is
believed to·have·the same pattern for-impulse as for-continuous:.noise:. .. simnarrw.~ may
therefore be applied when predicting iisk of impulse-NIPTS. T!leCHJ\BA;G-.1 DRC was ...
intended to protect 95% of the population; a relaxation of 3 dB may be. applied to obtain
limits for the 90th percentile. . ....
•' ._·, _ •. ,
Orientation ofthe Ear ... ··. · · ··.-.·· .. :: ...
.. ::-. . . Based·-on Hodge: &..McCommonsG-1•2• and' other data. CHABAG-t has;iecommend~d,i.i1' ·• · · .·
the case of gun noise, a penaltyof.S dB to apply when the noiSe strikesthe-•eardtuniat ·
norrrurl rather than grazing incidence~ Ifuncertainrit~ CbnS(lrvative u)aSSUJ11e.~ri9~~L ... ·.· ..
-· .. ~·incidenCe~· · · · ,_ .:··~ ·:--·· ·· .,,_ -· -··· -· _. · .. _ .... : ·
Combinations of Impulse and Con-tinuous Noise
Certain combinations of impulsive and continuous nois~, such as occur in irid'ustry
may be antagonistic-that is, one may provide some protection from the other-"-probably
because· of acoustic reflex activation. Other studies, however, show that the effects of
combined impulse and steady noise are additive.G-l,G-t 6 ISO, in its Recommendation
R/1999, G-17 proposed a flat weighting of 10 dB for "'impulsiveness" in distributed noise,
but the validity of this rule is questionable. On present evidence, it is probably safest to
G-8
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evaluate simultaneous impulsive and continuous noise separately, each according to its
own criterion.
Action ofthe Acoustic Reflex
This protective mechanism is valueless-in the.case of brief single or isolated impulses
because it has a latency of at least 10 ms and takes up to 200 ms before being fully effec-
tive. Rapidly repeated impulses, G-7 however, or simultaneous continuous noise,G-1s may
activate it sufficiently to provide up to 10 dB ofprotection: but this is too variable and
uncertain to be allowed for in damage risk criteria.
Audiometric Frequency·
Generally speaking, impulse nois~ affects the hearing in much the s~~e· w.ay' as does
continuous noise; with TIS and PTS begilUiing and :growing. most rapidly, at 4 to 6 kHz. It
. is possible, however, that impulse noise may have relatively more effect.on high:-frequency
·hearing or affect hearing al higher frequencies.~ll,G-14
Use of Equivalent Co11tinuous Sound Level (Leq) In Evaluation of Impulse Noise
Support forthe extensionofthe equal~energy (equivalent A-weighted sound energy)
concept of hearing hazard froin. continuous noise exposure to include impulse noise expo-
sure has recently been. gaining: ground. G-~9 · · At the 1970 Tedd.ingtori.Conference 0 n ••occu-. ·. ·
pational Hearing Loss''., it.was suggested that a .unifying rule based on this concept might
be drawn up to.link continuou5and impulse noise. exposure .limits in a single continuum·.
relating A-weighted sound level to ~ffeetive daily exposure duration. O:.lo ··.An empirical
formula enabling the A-weighted: Leq to be calculated from the pe~ sound pressure (ph) , .....
· repetition rate·iii impulses per second "(N).and the d-ecay constant of the fuip\ilse envelope ·
(k} in inverse seconds, was introduce<! as follow~: G-~1 .. . . . ..
. . ..
. .. ··. Le~-~-85.3+ 20~o~Ph-fo. ~-OlogN--l9,~og·k::to log(.l-tf~~)"
. . ·,·_. . . .. '· . . . .
where ·Ph is absolut_e pressure ~ :pascals; not. sound presslire l~vel in .dB .. For one i:Jnpul~e ..
of the B-type, this formulationmnplifiessuch that the~~ ofanA~weighted continuous
pulse ofdurationT. is equal to-the.peak.so"ilnd pressure:level (in dB) of aniiilpulsewhich
decays by 20dB.intime T minus9 dB •. The use. of this formula assumes tl;ie.intpulse is
comv,sed of broad-band noise.· that exponentially decays. This-relationship, ll;t the p~esent
time, should not be used to evil.luatiHmpul~~ d·~ta until"itjs further justifled by more
experimentaL research~ However, it·does provide further support of the equal energy con-
cept outlined.in,Appendix C --· . · · ··. . ·· ·· ·. ·
G-9
·::-.
·: ...
. , S~niary ami ,Conclusions. · · · · ·' .. ·· · ·
--~: .
. . ~ .. :~ ..
Hearing -Conservation
.. ;.',"···.· ......
. ~ . . ~ . .... : . ~
._ .....
·.:-···
~ ... . . ,· .. :.-·:. :, .. ·.
.. _ _. .. :·:::·.=:.: :: . :· '· ..... ·~:~ .. ; .·; .. ·· .
The following tule8 may be recom~end·ed if it 'is. desire:d. to prot~ct 9-6~.:~f-~h~ people· : ·
from significant impulse-NlPTS, that !s,from h.npulse-NlPTS ex:ceedfug s·da at4LkHzafter ·
lO:year.s·of repeated· exposures: · · · · · ·· · · · · . . .. . . . .
.·.·.· ... •.·· ..... · ... : .:. : .. ~ . ::. . . · ... · ... ~ . · ... ' : : -
. . L · ·. Measure or predictthe Pt?aklevei (SPL.}' and .A.: or B•type duration of the
impulse, using proper oscillogra.P.l:*.te9P.nique (NOTR: .... if the: noise is::~UffiC.iently.rapidly .':•·< .: ., ..... · ··.:
··: .... : repetitive to·fit Coles and Rice's G-7 . catl:lgory "C":;Jt. i:naY ~¢:_tl;eated and,)nea,s:uted .. as·con,:· . ' ... ..
tinuous noise and evaluated accardingly.jrt dBA. nU~-~a4ymeans ~-r~petitiott.rate .·. .·
·.exceeding 10/s).· ·.·.·:·. · ·. ..:~·., .:· ··· ..... -·· .. ·.··.·.;:·: ... ··:..... ···· ... : -> .. ·· · •·
. . . . . ·. . :. . : . . . : . "~ .
}. Use the"modifi~d. CHABAlimit" incFigure G,.l-to. determine the maximum
: permissible peakSPL.· If'in doubt:as.t6'imp~sebr.pe~ ... a8suitle B~uratitl11;·:~<:. ·. ·· : .. ···.··. · ··. · ··· .
···: .. ·.· . . :· ........ . ."·,: ·,; . ·>: ·-:~· ... :: ..... ::_. ···.::· .
3:· Ifthe numb~r of similar·impulse~.{r~J.experiem;ed•per:day exceeds;lOO;
reduce the permissible leV-el by 1 0. dB for every tenfoid :increase m N (e.g .. , 010 dB. when ·
N = 1000~ 20 dB when N = 10,000).
4. IfN. is less than 100, a higher peak level·.may.be allowed in .accordance with
. the same rule (e.g.,.l 0 dB more -when N..= 10), provic;ied.that..an absolut~maxi.mum.value
of 167 dB for:dUra.tions1essthan·2S mimseconds; grazingincldence (or 162 dB~-?rmai
incidence )-is not exceeded. · · .' ' ·· · · ... · ·' '" '.. · · · •' '; · ; · ...
.. :.· .... ··.-·
.... ,,. ·· · s·... Ifthe average repetitiOn rate' ofitnpu18es falls.in the range-0 .. 1 to lper ·.
second (i.e;, the average interval between impulses. is r tci lO seconds}, reduce the permissi•
ble :Peak level by 5 dB. . .
;_ ..
6; If the impulses are known to reaCh human ears in. the vicinity at grazing:
incidence, the permissible peak level may be raised by 5 ciB .. NOTE: This allowance
should be used with caution and must not be ·applied if the surroundings are reverberant.
If in doubt, assume normal incidence.
Effects Other Than on Hearing ·
See Section 3 in main document.
G-10
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SPECIAL NOISES
Infrasound G-26
Frequencies below 16Hz are referred to as infrasonic frequencies. Sources of infra-
sonic frequencies include earthquakes, winds, thunder, and jet aircraft. Man-made infra-
sound occurs at higher inten~ty levels than those found in nature. Complaints associated.
with high levels of infrasound resemble mild stress reactions and bizarre auditory sensations,
such as pulsating and fluttering. It does not appear, however, thatex.posure to infrasound,
at intensitities below 130 dB. SPL, present a serious health hazard. For the octave band .
· · centered atl6 Hz,., theA-weighted equivalent to 130 dB SPL is-7 6 dB(A).
·.· .. ·.
Ultrasound G-26
Ultra~onic.fr~quertcles are··those above iO,OOOHz. They are produced by a variety ~f ·
mdustrial equipment and jet engines. ·The effects of exposure-to high intensity ultrasound ... ·
.. ·. (above· 105 dB· SPL) are ·alsothe effects observed· durfu.g stress. However, diere. are ex peri~
· mental difficuities jn assessizlg-the. eff~cts of ultrasound since:.··
··· .. •.
. l. . •· Ultrasonic waves aie·hlghly absorbed by illr· .
2. Ultrasonic waves are often accompanied by broad~band noise and by
sub•haririonics'; . . -.
At levels below·IOSdBSPL, however, there have been:no·observed adverse. effects.
SONIC BOOMS ..
. ,-··. ·. . : .
Present·dayknowledge regardiilg the acceptability of sonic booms by man is base.d .. ·· ·
on observations: from both experimental field and laboratory studies and observations of
community response to actual sonic boom exposures. Individual human response to sonic
.· boom is very complex and involves not only the physical stimulus, but various.characteris-. . .
. . tics of the .environment as well as the experiences, attitudes and opinions ofthe po:imlation .· . . . . ..
··· ··-exposed.G-22 One of the most comprehensive studies to date on sonic boom exposure of
a large community over a relatively long period of time was the Oklahoma City study
conducted in 1964. G-23,G-24 Eight sonic booms per day at a. median .outd~or peak over-
pressurelevelof.57.46 pascals (or 1.2 psf)* were experienced by this community· over· a
*1 psf= 47.88 pascals
G-11
:. :··.
• •: • I
.. _ .....
... ··::·
'.· · .
. ;.: .. ~ .. : .
·:;._ ... :·····.·.:: ... ;·,,,.
:--· ...
:·.;· .. ,
6 month period.-Some results of this study are summari~ed·in Figure. era~:. For::eigh.tsoni9,
booms/day, there is clear· evidence that tbe~edian peak" .JVerpressure· mu~t-be· Well below . ·.
4 7.88 pascals {or 1 psf) if no annoyance is. reported:· ·when :mtei-Yiewed'~:~par{of~he popu~
lation considered eight sonic booms/ daytoJ>e un,a.cceptable:~ :l.ii;ext~p,Ol~tio~~;t~~· !~vel at
which eight sonic booms per day ShoUld be: acceptabl~·f or tli~': popul~~i.oH.~.:sligJl#y, less· :
·. than 23.94 pascals (or-o:s psf) ... :But eve~:at 23.94 pa5cii~ ~pproxima~~yi<)% oiJh~·popu
Iation consider themselves annoyed by an exposm .. e of eight sO.Ilic boom~/day;···ikear ' .
. . . . extrapolatio.nof the annoyance.data of Figtire G-3in.di~tt:s,t,hatarinoyiu:i~ewill· .. disappeax:. · ·
in the total population only when· the s .. sonic booms per day:·are less than 4~79 pa5cals~ A .
· ·lin eat extrapolation is probably not entirelyjustified; however;·as certainlY for-sonic booms ·
.. much less than ·4. 79 to 9.58 p~scals,-:a large percentage.-ofthe populat.ionis:rtot:¢ven / · ··
expected to sense the toom. The fa.ctthat the extrapolation must curve·isbestillusttated ·· · .··
····bythe interference curve of Figure G3~ Unless the extrapolhtioniscurtedas.'sho~ri, inter-·
·ference would. be predicted for abo~tc70% ~f the· p()pulation,~v~~ whe~;Jhe-~~·Qyerp~~~ · .•. · ·.
sure is zero; ie., no boom at all •. · · · .. :··· · · · . . .. • . ... :::.;: : . · . · : · :· ' < : ·
. ~··.· 100 .·
0 .....
t;·
~
r.:l 80
~
< 60'
~
t:
~ 40
·:···.· ·: ... .. '·.·: ··.;.··
. ~ .. : .. ~ . ·.
·t
I
0.0
0
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I
I
I
-· ,,..,.,. ... ·
/
/
......
• ..........
~ "' ...
0.5
25
.. :.· ... ; ....
L·S·•
MEDIAN PEAK OVE!iPRESSIJRE, .··lh/rt2 ..
50 75
MEDIAN PEAK OvERPRESSURE, N/m2 .
NOTE: Data compiled from Oklahoma City Study. Dashed lines are
extrapolations. All data for 8 sonic boom/day; G-'22
. ··,,:,.
. 2.0
100
Figure G3. Percentage of Respondents Reporting Adverse Reactions to Sonic Booms
G-12
. . ~·· . ··.. .. .
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So far the discussion has been about eight sonic boom exposures per day on a daily
recurring basis. The more difficult question is how to interpret the effect on public health
and welfare of sonic booms that are more infrequent than eight times per day. Kryter G-zs
provides a relationship which indicates that a sonic boom of 90.97 pascals once a day
would be equal to 110 PNdB or a CNR of 98 dB. It further suggests that the level (which
is proportional to P2 ) should be reduced by one half (3 dB) for each doubling of number
of occurrences. Froin Appendix A, Ldn is approximately related to CNR by Ldn = CNR
-35 dB. Thus, a CNR of 98 equals an Ldn of 63 dB. If the sonic boom is made equivalent
to an Ldn =55 dB, so as to be consistent with the levels identified in the interference/
annoyance section of this document, the level of one daytime sonic boom per day must l;>e _.
less than 35.91. pascals.· For more-than eight sonic booms/day; the level should be le-ss than
·. · 12AS pascals or. · ~J .. pascals. This result is slightly lower than the data from 'Figure . . _
G-,3, However, extrapolating the annoyance line in the figure suggests th-at the 12,45 ·
. ·:pascals levelof8· bobmswould annoy only 8%ofthepeople and more would fmd it un-. .
,acceptable.' Therefore, the relationship proposed is: dayti~e peak over-pressure per day,;, .... _· ·. :;.;r, ... _· l':ascals:where. N = nwnber of.soni<;:,booms/ d~y, · Thus~. the p~ak over~pressure o( · · ···. · .
a ~ii~C bot;>m·that-o:ecurs ~uring the day should be no-more. than 35.9 ~-paScals.:if.the _ ._. . · ·
popUlation is not to be annoyed or the general. health and welfare adversely affected.
. '• .. ·. _ .....
-;-_ .. :·· : .. ·.·,-
.. ;. . -'·
_ ....
. ' .. _ .. . -:·._;
·.·''
··,;:··: .-.. -.. -: ..
.. ··· _;'-
_ .. _; :-··-·
._··.,·: ·.· ".
The standard:sound level meter, which:is·a-time·averaging device, will not properly ineasure.the peak sound
· ·pressure level. of sonic booms.
G-13
. ,1"•:---..
.... :._;:"
G-1.
&2.
G-4 •.
... _,.
. . : . .
. . . .
REFERE,NCES FORAPPENI)IX-G -·
. ·~· ~·:.,·::~.' ~---~· ....... ·.:.:
Cl!ABA.,CWard, et .. ·ai-;:·i•968·)~--·~Proposedo~~~~~~·triterio1{ro~,tm{lui~~No~~---_
(Gunfire)," (U). Repart,of.WorkingGro~p-57;~ NA&NRct:oiruriittee b.t1 H~aring,
·-· Bioacoustics, and Bi~mechanics· (CI{ABA)t;W;: DixonWard;:Ch'aibna,ri~Washlngton,
D~C: Office ofNaval: R~ch. ·. ' · · '·· : '· '· <;.:·•;c, . --·. -' ·
··.··;:·:" ."· , . . • .. ·~· . . . : ,· ..
· Guignard~ J~ C., "A ·Basis for 'LinritingNoiSe Expo5ure·forHe~:~n~rVation~"·
Aerospace M~dical. R~~e:af~ I;.<i~ratOty.~ Wti~t;-}>9ttetson ·Alr: Eor.c~,.Jlase·; Ohio ·
and EnVii-onmentill PTo.tectio~ A,;gency, W!!Shing~on" D~(;.: . Joint'EP,A/USAF-Study
. M1RL,.TR•73~90' and ·EP A ... ss&t~13'<i0l;.;\;,: 1~7:3'~-. ..·· ;.-· . . . . ··_ ·-•
•:. . •·.· . . . . . . . .. : . •. •. . •. : .. . .. :. •. ~ ~ ·.... ... ··:.""! .. · .•.. ;··, · ... • .. ••.• : •.
--M.cRobert, H. arid Wat:d, · W~ D,,;''Damage~Risk'..Criteria~-The Tradirig Relation
Between Intensity ~d the Number:of}~onreverberan_t Impulses,••· Journal of
Acoustical Society o{Ameriiil< 5$; 1297;;1300; 197'3-• . . .·. '
: ... \ ~ : . . . . ·. :: ... : . .
Poche, L. k, Stockwell, c~"W._ and Ades, H~ )V~; "Ci:>chlear Hau~ell rian;age in ,
Guinea Pigs After Exposure to· Impulse Noise/' Journal of Acoustical S.oci'ety of
America, 46: 947-951, 1969. ·.. · · . ·. . .
-:· .... , -~ .
G-5. Majeu.Chargois, D. A., Berlin, C. I. and Whitehouse, G. D., "Sonic. Boom Effects on
the Organ of Corti,u Laryngoscope, 80, 620-630, 1970.
G-6. Coles, R. R. A;, Garinther, G. R., Hodge, o, c. and' Rice~ C 'G;("Haiatdous'lixp:O-
sure to Impulse Noise,".Journ.a/.of .l}.co.ustical:Societyof A1'.1re.rica;:,'43:'·336-343; · 1968.. . . _· · ...... ' .-. . .. ·_ ... " .. -.:.. ' ·· ...... ·· . . .
.G-7. . Coles, R. R. A~ ~~d Rice; c .. G~ ... Assessment of RiSk ofHear~g LOss Due t~ .·
Impulse Noise," Occupational Hearing Lo-ss;_ ed.; ;l~,o:binson,;I).;. \V:., Londoil& Ne~
York: Acadenrlc Press; 71-77, 1971. ,, ., · ,· · ---. ·-·-..
G-8. Ward, W. D., Selters, W. and Glorig, A., "Explorat~ry St~dies· ort Temporary
Threshold Shiftfrom Impulses," Journal ofAcoustica/ SoCiety of America, 33:
781-793, 1961.
G-9. Luz, G. A. and Hodge, D. C., "Recovery from Impulse-Noise Induced TTS in
Monkeys and Men: A Descriptive Model," Journal of Acoustica.lSociety of
America, 49: 1770-1777, 1971.
G-10. Loeb, M. and Fletcher, J. L., "Impulse Duration and Temporary Threshold Shift,"
Journal of Acoustical Society of America, 44: 1524-1528, 1968.
G-14
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G-11. Kryter, K. D., "Evaluation of Exposures to Impulse Noise," Archives of Environ-
mental Health, 20:624-635, 1970.
G-12. Hodge, D. C. and McCommons, R. B., "Reliability ofTTS from Impulse-Noise
Exposure," Journal of Acoustical Society of America, 40: 839-846, 1966.
G-13. See Reference G-10.
G-14. Fletcher, J. L., "Effects of Non-occupational Noise Exposure on a Young Adult
Population," Report for Department of Health, Education and Welfare, NIOSH:
HSM 099-71-52, Washington, D.C., HEW, 1972.
G-15. Cohen, A., Kylin, B. and La Benz, P. J. "Temporary Threshold Shifts in Hearing
from Exposure to Combined Impact/Steady-State Noise Conditions," Journal of
Acoustical Society of America, 40: 1371-1379, 1966.
G-16. Okada, A., Fukada, K and Y amamura, K.; "Growth and Recovery of Temporary
Threshold Shift at 4kHz Due to a Steady State Noise and Impulse Noises," Int z
angew Physiol, 30: 105-111, 1972.
G-17. International Organization for Standardization (ISO), "Assessment of Occupational
Noise Exposure for Hearing Conservation Purposes," ISO Recommendation ISO/
Rl999, Geneva: ISO, 1971.
G-18. Kryter, K. D. and Garinther, G., "Auditory Effects of Acoustic Impulses from
Firearms," Acta Oto/arying(Stockh), Supplement 211, 1965.
G-19. Coles, R. R. A., Rice, C. G. and Martin, A.M., "Noise-Induced Hearing Loss from _.
Impulse Noise: Present Status," Paper to International Congress on Noise as a
Public Health Problem, Dubrovnik, May 13-18,.1973.
G-20. Martin, A.M., In discussion, 1970 Teddington.Co.riference on Occupational Hea;ing ·
Loss, ed.; Robinson, D. W., London-and. New York: Academic Press; 89-90, 1971.
G-21. ·.Mart~, A.M. and Atherley, G. R. C., "A Method for the Assessment of Impact
Noise with Respect to Injury to Hearing," Annals of Occupational Hygiene, 16: 19-
26,1973. . . . ..
G-22. von Gierke, H. E. and Nixon, c. w., "Human·R~sponsesto Sonic-Boom in· the
Laboratory and the Community," Journal of Acoustical. Society of America,
51:766-782.
G-15
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·.
G-23. "Noise as a Public HeaUhHazard," Proceedings. of the National Conference on the
American Speech and Hearing Association, June 13-14, 1968, D.C., Report 4,
February 1969.
G-24 •. Borsky, P. N., "Conununity Reactions to Sonic Booms in the Oklahoma City Area,"
National Opinion Research Center, AMRL-TR-65.,37, 1965.
G-25. Kryter, K; D., "Sonic Booms from Supersonic Transport," Science, 163: 359-367,
Jan~ 24, 1969. . ~
G·-26. Public Health and Welfare-~riteria·for N<;>ise, Environmental Protection Agency,
550/9-73-002, July 27, 1973.
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G-16
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