HomeMy WebLinkAboutAPA2240lva1cott,C.1974.The homing of pigeons.Am.Sci.
62:542-552.
Walkinshaw,L.H.1956.Sandhill cranes killed by fly-
ing into power line.Wilson BulL 68:325-326.'
Ward,A.L.,J.J.Cupa1,A.L.Lea,C.A.Oakley,and
R.lv.lveeks.1973.Elk behavior in relation to cattle:;!
grazing,forest recreation,and traffic.Trans.N.Am.
Wi1d1.Nat.Resour.Conf.38:327-337.
West,H.J.,J.E.Brown,and A.1.Kinyon,'.1971.
Simulation of EHV transmission line flashovers in-
itiated by bird excretion.IEEE transaction paper
71 TP l45-PlolR.'
Willard,D.E.,and B.J.Willard.Unpubl.ms.
The interaction between some human obstacles and
birds.
Western Interstate Commission for Higher Education
Boulder,Colorado
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Effects Of Noise On Wildlife
Dennis B.Griffith
Jaok M.Lee 3 Jr.-
Bonneville Power Administration
Portland,Oregon
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Anchorage.AK 99508.4614
TRANStuSSION LINE AUIlIBLE NOISE AND lVILDLIFE
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INTRODUCTION
Transmission line rights-of-way have been a conspicuous
part of the landscape for many years.Until the advent of
extra high voltage lines (EIIV,above 230 kV)it was often
assumed that transmission lines had a net beneficial effect
on wildlife due to the increased habitat diversity pro-
duced by cleared rights-of-way (Egler 1953,1957).
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When the first EHV transmission lines were constructed
in the U.S.during the 1950's the transmission facilities
themselves began to be a more noticeable component of the
right-of-way environment and new kinds of environmental
impacts were identified.These included greater visual im-
pacts due to the larger physical size of the facilities and
electric field and corona effects due to the higher operating
voltages.Of the latter effects,audible noise (AN)due to
corona (air ionization)was found to be a source-of annoy-
ance to persons living near EHV lines (Perry 1972).Con-
cerns have also been raised about the possible effects of
transmission line AN on wildlife (Klein 1971,Villmo 1972,
Martinka 1974,Driscoll 1975,Fletcher 1975,Balda and
Johnson 1976,Grue 1977).
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Noise is usually defined as unwanted sound.It can
also be described as an environmental pollutant which is a
waste product generated by various human activities (EPA
1974).In general,wildlife species are expos~d to many of
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106 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 107
the same environmental noises as man.A recent report in-
cluded an estimate that as many as 13 million American live
in places where noise from cars,buses,trucks,airplanes,
construction equipment,and electrical devices may b~
harming their health (Comptroller General 1977).
Although the hearing ability of wildlife varies greatly
among species and may differ significantly from man,a
knowledge of the effects of noise on wildlife aids in under-
standing the effects of noise on man and vice versa.The
concept of wildlife as an indicator of environmental quality
has been described by a number of authors (Thomas'ct al.
1973,Jenkins 1972).
Noise can produce in man and animals such effects as
hearing loss,masking of communications,behavioral changes,
and non-auditory physiological effects ·(EPA 1974).For
wildlife in natural environments,the most observable effects
of noise would seem to be changes in animal behavior due in
part to the masking of auditory signals.Most wildlife are
mobile and could in theory avoid areas of intense noise
levels necessary to cause permanent hearing damage.
It is well known that noise can cause great behavioral
changes in wildlife.Beginning \vi th the human voice and
the clap of hands,and progressing to explosives and more
recently to sophisticated sonic generators,man has used
noise to repe1l animals from areas where their presence re-
sults in damage to crops or other property (Frings 1964,
Busnel and Giban 1968,Stewart 1974).
A report published in 1971 by Memphis State University
summarized much of what was then known of the effects of
noise on wildlife and other animals (Memphis State Univ.
1971).Of the 103 references cited in the report only one
made any reference to the effects of power line noise on
wildlife.This single report consisted of a brief mention
that the "hum"from power lines (no voltages or sound
levels given)adversely affected reindeer (Rangifer tarandus)
behavior and contributed to difficulties in herding (Klein
1971).
A report by the U.S.Environmental Protection Agency
(EPA 1974)identified a need for information on the effects
of noise on wildlife.Included in the report were re-
commendations for studies to determine the effects on
animals of low-level,chronic noise,and for comprehensive
studies on the effects of noise on animals in their natural
habitats.The subject of this paper is the possible effects
of relatively low-level transmission line AN on wildlife in
natural environments.
This paper has the following objectives:
1)To describe the characteristics of transmission
line AN and its effects on the human environment.
2)To relate these effects to the possible effects of
AN on wildlife,
3)To relate the effects of AN to the overall effect
of a transmission line and associated right-of-way,
and
4)To describe research efforts of the Bonneville
Power Administration (BPA)which are beginning to
provide information for evaluating the effects of
AN and other transmission line parameters on wild-
life.
The effect of transmission line AN on wildlife is most
reasonably considered when in the context of the overall ef-
fect that transmission lines have on wildlife.Noise from
corona discharges is only one component of the complex
environment that exists in the vicinity of a transmission
line right-of-way.In addition to AN,wildlife on a right-
of-way ~.y be simultaneously exposed to human activity on
access roads,shiny metal towers and conductors,electric
and magnetic fields,and chemically-treated vegetation.It
is a complex undertaking'to determine the singular or
combined impact of these components on various wildlife
species which have Widely differing biological and ecological
characteristics which vary with season,weather,and habitat
conditions..
TRANSMISSION LINE CHARACTERISTICS
An understanding of general transmission line charac-
teristics is necessary to place the effects of AN in proper
perspective.Although this discussion of transmission line
construction,maintenance,and operation characterisitics
relates primarily to the BPA transmission system,much of
it will apply to transmission lines in general.
Transmission lines carry electrical power from genera-
tion sources to load Centers.There the power is trans-
formed to lower voltages in substations for distribution
over smaller lines to users.
As an indication of the extent that transmission lines
have become a part of our environment,consider that in 1970
Transmission structures vary greatly in shape and size
depending on such factors as line voltage,topography,
esthetics,and technical and safety design considerations
(BFA 1975).EHV transmission lines usually require metal
towers to support the weight of conducting wires (Figure 2).
In some cases one structure supports two electrical cir-
cuits.This results in a significan t decrease in right-of-
way width required compared to that needed for two single
circuit lines but requires the use of taller towers.
The trend has been to build transmission lines with
higher operating voltaees because the power carrying
capacity is significantly increased with increases in
voltages.For example,a 1200-kV transmission line c~uld
carry approximately six times the power carried by a single
circuit 500-kV line but would require a right-of-way only
15.4 m wider (BPA 1976a).Presently,765-kV is the ~highest
a-c voltage for operational transmission lines in the U.S.
BPA has constructed a 1100/1200-kV prototype transmission
line and lines of this voltage are expected to be in use in
the U.S.in the 1980's.
there were an estimated 480,000 km of transmission lines in
the United-States (USDI and USDA 1970).The BPA system
alone in the Pacific Northwest consists of over 20,000 km of
transmission lines (Figure 1).Of these over 5,600 km are
345 kV and above.It has been estimated that for the
balance of this century approximately 160,000 km of nN"
transmission lines will be constructed on 60,700 ha of right-
of-way each decade (USDI and USDA 1970).It is unlikely that
underground transmission will be used to any great extent in
the next few decades due to the high costs involved (Truax
1975)•
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108 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
Construction
Transmission line construction usually involves vege-
tation clearing,access road construction,tower footing
installation,tower assembly and erection,conductor
stringing and site restoration (BPA 1974).The environmental
impact of this construction varies widely depending on such
factors as size and length of line,topography and vegetation
types encountered,weather,and time of year during which
construction occurs (Goodland 1973).In general,lines
constructed in steep forested areas where many new access
roads are required result in the greatest impact during the
construction phase.At the other extreme,lines constructed
through level grassland may result in comparatively few Figure 1 -Bonneville Power Administration Service area
showing E.H.V.transmission lines (345 kV,5QO kV,~kv d.c.).
Figure 2 -Configurations of typical B.P.A.transmission
structure.Scale is approximate.
1JJ'JI
TRANSMISSION LINE AUDIBLE NOISE 111
II
On older transmission lines a cleared right-of-way
through forest habitat is one of the most characteristic
features of a transmission,line right-of-way.On some
newer lines more selective clearing is practiced resulting
in a "feathered"appearance.
Access roads can also be a primary feature of a trans-
mission line right-of-way especially in forested areas.
Roads are required for both constructing and maintaining
transmission lines.Althou~l existing roads are used where
possible new roads are often required both on and off the
right-of-way.toJhere access roads are constructed across
public lands such roads can receive heavy use by recrea-
tionists including hunters,campers,fishermen,and off-
road vehicle enthusiasts.Increased human access to pre-
viously remote areas can have significant consequences for
wildlife,especially those species that require wilderness
type habitat.
environmental impacts during construction.
As indicated above,construction of a transmission line
can result in significant environmental disturba~ces.The
resulting impact of construction on wildlife can be reduced
in some cases by the USe of mitigation measures (EPA 1974,
USDI and USDA 1970).
The final stage of construction consists of removing
all equipment,and material,and debris and restoring dis-,
turbed sites.Unmerchantable trees and brush removed from
the right-of-way and access roads are usually burned on
the construction site.Tower sites and other disturbed
areas are recontoured.Disturbed areas are often seeded to
facilitate the regrowth of vegetation.
Quantitative information on the above types of impacts
of construction activities on wildlife is rare.BPA line
construction personnel have reported that deer (Odocoileus
spp.)and elk (Cervus canadensis)are frequently observed
near construction sites.Other more secretive species may
avoid construction areas although during construction of the
BPA prototype ll00/1200-kV line a cougar (Felis concolor)
observed near the right-of-way did not app~o be greatly
disturbed by the activity of men and equipment.Construction
activity at the site did not appear to have any large effect on
on the abundance of birds and small animals.Stahlecker
(1975)reported that wildlife activity cea;sed when workers
were constructing a 230 kV transmission line in Colorado.
He also found that survey stakes,tower material and other
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SINGLE CIRCUIT 230 KV
FLA'T'"""CQNfTGU RAT ION
SINGLE CIRCUIT 500 KV
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TRANSMISSION LINE AUDIBLE NOISE
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JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
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equipment were used as singing perches by some birds.He
reported that construction activity may have caused some
birds to desert their nests.Other than possible adverse
effects on Ord's kangaroo rat (Dipodomys ordi)due to de-
struction of burrows,he found no evidence that other small
mammals were adversely affected by construction.nalda
and Johnson (1976:7-18)reported that construction of two
500-kV transmission lines in Arizona resulted in drastic
differences in the species diversity of small marronals but
that the differences were transient in nature.
Maintenance
There occurs during the operating life of a transmi.ssion
line a variety of activities to maintain the facilities and
insure high system reliability.Of primary interest as far
as wildlife are concerned are vegetation management acti-
vities.Brush and treeS on rights-of-way are controlled
so that they will not grow into conductors or impede resto-
ration of service if outages occur (BPA 1974).Vegetation
management is accomplished in a variety of ways including
both mechanical cutting and chemical treatments.The re-
sult,in forested areas,is that plant succesion is main-
tained in a shrub/grass stage.
Cleared rights-of-way are probably utilized by most of
the same wildlife species that inhabit the adjacent forest
(Cavanagh et al.1976).In some cases the right-of-way
may attract species and communities which differ from those
found in the original forest (Schreiber et al.1976).The
"edge effect"has been used to describe the phenomenon where
wildlife utilize areas of overlapping habitat types to a
greater degree than they utilize the adjoining habitats
(Odum 1959).Several studies have documented the effects
that clearings,whether man made or natural can have on
wildlife (Lay 1938,Edgerton 1972,Walmo et a1.1972,Pen-
gelly 1973,Patton 1974).
For transmission lines the width of the cleared right-
of-way can be an important consideration.Anderson et al.
(1977)found that in deciduous forests a 12 m wide right-
of-way had reduced bird species diversity compared to the
adjacent forest.A 30.5 m wide right-of-way had high bird
species density and diversity and a 91.5 m wide right-of-
way had less diversity but attracted species not found in
the adiacent forest.
Although herbicides are recognized as potentially
hazardous to wildlife,with proper application techniques
they can be used effectively to control right-of-way vege-
tation while only minimally affecting non-target organisms
(Buffington 1974).Since 1970 BPA has sponsored researchtoevaluateherbicidesuse9ontransmissionlinerights-of-
way (Norris 1971).This research also shows that these'
chemical.s can be used without noticeable adverse effects to
animals.Buffington I s (1974)review pointed out some pos-
sible effects of herbicides on wildlife which have not re-
ceived a great deal of attention.These include the pos-
sible adverse effects of herbicides on rumen flora of large
herbivores.
Mayer (1976)studied wildlife usage of power line (no
voltages give~)rights-of-way in the easfern U.S.which had
been maintained by the use of herbicides.Wildlife species
included whitetail deer(Odocoileus virginanus)ruffed grouse
(Bonasa umbellus)gray squirrel (Sciurus carolinensis)bob-
white quail (Colinus virginianus),and cottontail rabbit
(Sylvilagus floridanus).Results of the study showed that
wildlife utilized the rights-of-way to a greater degree than
they utilized habitats adjacent to the right-of-way.
Vegetation on rights-of-way can also be controlled by
selectiye cutting and this can also have an effect on wild-
life usage.Cavanagh et al.(1976)found that wildlife
usage of selectively maintained powcrlinc (no voltage given)
rights-of-way was higher than usage of clearcut rights-of-
way.Costs for selectively maintaining the rights-of-way
was approximately 12 times that required for maintaining
the clearcut rights-of-way.
Operation
The electrical properties of an operating transmission
line result in field effects and corona effects.A con-
sideration of the electrical effects of transmission lines
is necessary in both the design of biological studies and
in the interpretation of results.The following is an in-
troduction to the electrical characteristics of EllV tr.ans-
mission lines.Persons unfamiliar with transmission lines
contemplating biological research in this area should seek
advice and assistance from persons with training in such
fields as electrical engineering and physics.
Field Effects
Voltage applied to a transmission line conductor pro-
duces an electric field in the region surrounding the con-
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH114
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TRANSMISSION LINE AUDIBLE NOISE 115
1
ductor and extending to the earth.Current flowing in a
conductor produces a magnetic field.At a corr~on measure~
ment height of 1 m above ground,the maximum electric field
strength (voltage gradient)beneath BPA 500-kV lines with
a conductor to ground clearance of 11 m is about 8-kV/m
(BSTT 1977).The electric field strength near an a-c trans-
.mission line can be measured with a hand-held meter available
from various manufacturers.Field strength can also be cOm-
puted (Deno and Zaffanella 1975).The maximum magnetic
field strength of such lines is approximately .6 Gauss
(BSTT 1977).The electric field strength beneath 765-kV
lines,wi tll a conductor to ground clearance of 17 m is 9-10
kV/m (SNYPC 1976).These maximum field strength levels
occur in a relatively small area at mid span beneath the
conductors.At the edge of a 500-kV transmission line right-
of-way maximum field strength is from 2.5 -3.5kV/m (BSTT
1977).Maximum field strength beneath BPA 230 kV lines is
3-4 kV/m.For reference,the electric field strength 30
cm from an electric blanket is approximately 0.25 kV/m and
60 Hz electric fields inside a typical house may range from
less than 0.001 kV/m up to 0.013 kV/m (Miller 1974).
When conducting objects such as vehicles,persons,or
animals arc in an electric field,currents and voltages are
induced in them (BSTT 1977).Usually these currents and
voltages are belOW the perception level for humans.Under
certain circumstances annoying spark discharge shocks can
occur to people and animals in the vicinity of transmission
1:[110:->.ThcRC Ch"Clllll.<,tanccs occur when a person or aniTlk'll,
insulated from ljround,comes in contact with a grounded
object,or when the object is insulated and the person or
animal is grounded.Such shocks are similar to what one
experiences after walking across a carpet and touching a
door knob.Conducting objects near transmission lines such
as metal fences are routinely grounded to prevent the build-
up of large voltages on such objects (BSTT 1977).The
magnetic field can also induce voltage and currents al-
though the effects arc not as apparent as for the electric
field.
The presence of electric fields can also be sensed if
the magnitudes are great enough.Deno and Zaffane1la (1975)
reported the threshold for perception of an electric field
(e.g.,hair stimulation)for the most sensitive 10 percent
of the persons tested was between 10 and 15-kV/m.We have
felt hair stimulation on our extended arms beneath a BPA
500-kV line with an estimated field strength of 7-8 kV/m.
When standing on dry ground with rubber soled shoes,we
could also perceive a slight tingling sensation when touching
vegetation.
Relatively little is known about the perceptton of
animals to electric fields.In one study there were no
visible changes in grazing"feeding,and drinking habits
of cattle on damp ground in electric fields of l8-kV/m
(Deno and Zaffanella 1975).Those authors,however,sug-
gested that on dry ground,spark discharges might occur
between grounded objects and the bodies of animals.Re-
searchers at Battelle Pacific Northwest Laboratories saw
no hair movement on the ear of an anesthetized swine until
field strength reached 50-55 kV/m (Phillips et a1.1976).
Radar tracking studies conducted by Larkwin and
Sutherland (1977)suggested that during nocturnal migratory
flight,birds were apparently able to sense low intensity
a-c (72-80)electromagnetic fields produced by a large
antenna system.The two antennas used in the study were
each 22.6 km long and 8 m above ground.They produced
an electric field of 0.07 VIm at 100-400 m and the magnetic
field at these distances was less than 1 percent of the
earth's magnetic field.
Lott and 11cCain (1973)used implanted electrodes to
determine if rats were aware of an external electric field.
~len in a d-c positive field of at least 10 kV/m rats showed
a statistically significant increase in brain activity (EEG)
which was reported as an'indication the rats were aware of
the field.
In recent years considerable interest has ar~sen OVer
the question of whether low intensity electric and magnetic
fields can result in biologic effects as a result of long
term exposure (Young and Young 1974,Llaurado et al.1974).
At the present time the bulk of the available evidence does
not indicate that transmission lines pose a significant
biological hazard in this regard (Bridges 1975,BSTT 1977,
Janes 1976).Additional information'is needed,hm"ever,for
assessing the potential for such effects.
In addition,studies done on the biologic effects of
ions at concentration levels similar to those produced by a
d-c transmission line suggest both beneficial and adverse
effects are possible (Krueger and Reed 1976).Several
studies are underway in the U.S·.which should provide more
definitive information on the nature and significance of
biologic effects from electric and magneti~fields.A review
of the above topics and listing of this research can be
found in a BPA publication (BSTT 1977).
It should be pointed out that d-c electric field
strength values cannot be directly compared with a.c.values.
Even with d-c electric fields of 40 kV/m the current inter-
cepted by persons beneath a d-c tramsmission line is many
times below the perception level (Hill et al.1977).The
probability of receiving perceivable spark discharge shocks
in the proximity of a d-c line is also less than for com-
parable o-c lines (Hill et al.1977).
A d-c transmission line has similar electrical para-
meters as an a-c line,however,there are some differences.
Corona-generated ions from a d-c transmission line form a
"space charge"which alters the elec tric field near 'the line
(Hill et al.1977).Ions are greatly affected by wind and
consequently the ground level electric field for a d-c Hne
frequently changes in location and magnitude.On the Celilo-
Sylmar ±400-kV d-c line electric field strengths of -34 kV/
m have been measured with approximately half of this due to
enhancement by the space charge (Bracken et al.1977).
Audible Noise (AN)
Depending on such factors as line voltage,conductor
design and surface irregularities,and weather,transmission
J
Corona discharges result in power losses and therefore
a-c transmission lines are designed to operate in fair
\veathcr below the corona onset level.A common design is
the use of a number of subconductors to transmit the power
in each of the three phases of an a-c transmission line
or the two poles in the case of a d-c line.This has the
effect of increasing the overall surface area of the con-
ducting material.This reduces the voltage gradient on
the conductor surface and thus reduces the occurrence of
corona.
line AN can vary Widely.It is n~st noticeable on a-c
lines of 500 kV or higher.For such lines the noise is
characterized by a random broadband,crackling,hissing
sound with a 120 Hz "hum"or harmonics of this frequency
occasionally present.The ~haracteristics of AN from d-c
transmission lines is described later in this section.Al-
though usually termed "audible noise",corona noise actually
extends to frequencies above the limits of the human hearing
range (lanna et al.1973).
In reality corona can occur with EHV lines even during
fair weather because of imperfections or contaminants on
the conductors.Although nicks,scrapes,insects,and dust
can caus~corona,water on the conductors is the most im-
portant cause.A-c transmission line AN is generally highest
during heavy rain.Ambient noise,however,is also high
during heavy rain so AN is more apparent during snow,fog,
light rain,mist,or just after a rain while the conductors
are still wet.
J ill 1 I
TRANSMISSION LINE AUDIBLE NOISE 117
The age of the conductors also has an effect'on the
amount of AN produced.The ,surface of a new conductor has
a light coating of grease which causes water droplets to
form over the entire conductor surface (Perry 1972).As
the conductor ages,corona and weather combine to change
the conductor surface conditions so that water droplets
tend to form only on the underside of the conductor.This
reduces the effective number of corona discharge'points and
lowers AN compared to the new conductor.AN may reach its
highest levels during the first few years after a line is
constructed which is also the time when the "newness"of the
overall facility may have its greatest effect on wildlife.
Other factors which can affect AN production include the
configuration of the sub conductor bundles,phase spacing
and phase configuration,height of the con9uctors above the
ground,and proximity of other circuits which may be on the
same transmission structure or on adjacent ones.
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For reference,the earth's d-c electric field averages
0.13 kV/m and beneath thunderclouds levels of 3 kV/m or
higher may exist even in the absence of lightning (Polk
1974).The magnetic field of a d-c line is approximately
the same level as the .6 G d-c field of the earth.
The subject of transmission line AN has been dis-
cussed in a number of papers (Perry 1972,Ianna et al.1973,
Comber and Zaffane11a 1975).What follows is a summary
of pertinent aspects of corona produced noise which pro-
vides a basis for determining the possible effects of such
noise on wildlife.
When the electric field intensity on the surface of
a transmission line conductor exceeds the breakdown strength
of air,corona dischrages occur (Deno and Comber 1975).
Corona results in AN,radio and television interference,
,flashes of light,and production of oxidants (primarily
ozone).Of these,AN is probably the more important as
fat as possible effects on wildlife are concerned.Studies
have shown that the amount of ozone produced by trans-
mission lines is generally not measurable above ambient
levels (Sebo et al.1976,Roach et al.1977).
116 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
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118
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TRANSMISSION LINE AUDIBLE NOISE 119
CUMULATIVE PERCENT OF TIME LESS'THAN ORDINATE
Figure 4 -Cumulative frequency distribution for audible noise
from a 500 kV a-c transmission line with one 6;35 em conductor
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Note that AN levels measured at various distances from a
transmission line are functions of distance and the combina-
tion of random noise and hum generated from each phase of the
line.The strength of the 120 Hz hum can vary several dB
as a consequence of displacing the measuring microphone a
few meters..
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40 I 1""'-I I I 'I I
w
Vl LL50
Z a:
w w
..J ...
a:I Z_w
o u
='
q;5
II:
LL
E
0M
In determining the environmental effect of transmission
line AN it is important to consider it in relation to ambient
noise levels.If the AN measured for a transmission line
is at least 10 dB above ambient,the measured AN is es-
sentially from the line (Comber and Zaffanella 1975:197).
Those authors further indicate that when differences mea-
sured between ambient and the transmission line are 3 dB
or less the two conditions cannot be separated by con-
ventional measures.It should be pointed out that the
above refers to measurable levels.The AN may still be
audible even when the level is similar to ambient due to
its unique frequency characteristics.
As described above,AN varies greatly in intensity and
frequency composition depending on a number of factors
foremost of which is weather.In considering the possible
effects of AN on wildlife,it is important to keep in mind
that animals that may inhabit areas near an a-c transmission
line right-of-way are not exposed to a constant level of
noise.Figures 4 and 5 are examples of the kinds of varia-
tions in AN which can be'expected from EHV transmission
lines.70 I""I------r,-----,1-----,-1---....,----,-,.....,
>-~u.I I I I -.J-t x 6.35 em
9
<{...60 I I ~I I -..--:.-.J IcoG/I ::::::::012 x 4.07 em"C -II:
a:I
"C
w 65Vl
i5z
w 60..J
a:I
0
:l
<l:
55
70 I A I I I I
75
dB(1251
Figure 3 shows a lateral profile of AN measurements
for a 500-kV line during rain.
Analysis of transmission line AN should include both
the broadband and the pure tone components.The 120 Hz hum
(and other multiples of this tone)is produced by the rapid
oscillation of ionized air ions near the conductor surface
which have been generated by corona.Although the 120 Hz
hum correlates with corona,the relative magnitude of the
random noise and the 120 Hz hum can differ depending on
weather conditions.The 120 Hz hum does not attenuate as
rapidly as the high frequency random noise and it therefore
may be detected at greater distances from the transmission
line.At certain times in central Oregon with ambient noise
levels of approximately 20 dB(A)we have heard the hum from
two 500-kV a-c transmission lines from almost 2 km away.
A standard procedure for making measurements of trans-
mission line AN has been developed (IEEE Committee Report
1972).Measurements of AN are often reported in dB(A).The
"A"weighting network discriminates against lower frequencies
including 120 Hz.so dll(A)n~asurements of AN actually per-
tain primarily to the random noise (Conmer and Zaffanella
1975)•
50 'I I I ,I I J
o 15 30 45 60 75 90
HORIZONTAL DISTANCE FROM CENTER OF RIGHT·OF·WAY (METERS)
Figure 3 -Typical lateral profile of audible noise from a
500 kV a-c transmission line with one 6.35 em
conductor for each phase.Adapted from Perry
(1972).
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE120
J I ))J ]'r j I i 1 I 1 J J J
121
95%"50%1 ~~~
-5'7'0~--./......-.1~~....,~-
'"-..........
70
~60
«
w allila00:zS!50
w~
-J'"68 40
::;.'«w
0:
i'ii
'0 30
95%~
50%1 ~"5%'"N ~~
""'-....,....~-....
"""l
)
~......
--'
~
70
~60
«
alwQ~a:50ou
z~
W'"-J o~8 40o·::J w«a:
~30
20
Figure Sa -
63 125 250 500 1000 2000 4000 UOOO dB(A)
FREQUENCY.Hz
Audible noise spectrum during fair weather or a
775 kV a-c test transmission line with four 35.1
rom diameter conductors per phase.Noise level
is less than the ordinate the indicated percen-
tage of time.Redrawn from Kolcio et a1.(1973).
20
Figure 5c
63 125 250 500 1000 2000'4000 8000 dB(A)
FREQUENCY,Hz
-Audible noise spectrum during rain for a 775 kV
a-c test transmission line with four 35.1 rom
diameter conductors per phase.Noise level is
less than the ordinate for the indicated percen-
tage of time.Redrawn from Kolcio et al.(1973).
Although there is no difference in the mechanism of a-c
and d-c corona,there are sufficient differences in AN
associated with the two types of transmission lines to war-
rant 11 brief discussion.This discussion is based pri.marily
on information contained in a recently published reference
book on HVDC transmission (Hill et al.1977).
Unlike three phase a-c lines,a d-c transmission line
has only two sets of conductors (poles),one negative and
one positive.The positive pole is the primary source of
AN.The noise is characterized by impulsive pops and is
similar to the random noise of the a-c line without the
120 Hz hum.The frequency characteristics of the d-c AN
are generally similar to the a-c random AN.
A major differnce between the two types of lines is that
d-c corona loss is less affected by weather than'is a-c.
Correspondingly,as compared to a-c lines,AN from a d-c line
changes less between fair and inclement weather conditions ..
Studies with a d-c test line at the Dalles,Oregon showed
that rain may even cause a very slight decrease in d-c AN
levels and snow had no significant effect (Hill et al.1977:
67).Maximum AN 'levels measured for the d-c test line
ranged from 30 dE(A)with the line operating at ±400 kV,
to 48 dB(A)at +600 kV.Note that for a d-c line,voltage
is usually reported as the difference in potential between
the positive and negative poles and ground.Sometimes the
63 125 250 500 1000 2000 4000 8000 dl3lA)
FREQUENCY.Hz
_Audible noise spectrum during fog for a 775 kV
a-c test transmission line with four 35.1 rom
diameter conductors per phase.Noise level is
less than the ordinate for the indicated percen-
tage of time.Redrawn from Ko1cio et a1.(1973).
95%""~50%'-~--.---.....w-
5%~~"......-l~~r -----I
\~
.-
I ..........
~
20
70
Vi"60a:«
QJWo
!::2 a:50auZ:e
w'"...Jo~8 40o.
:::lw«'a:
~30
Figure 5b
1 j J 1 1 ]
'f
}J J 1 1 )~
122 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 123
operating voltage is reported as the total potential be-
tween the two poles.In this latter caSe +400 kV d-c
would be reported as 800 kV d-c.
To gain a better understanding of how AN from trans-
mission lines could affect wildlife one can first consider
fts effects on people.For reference,Table 1 shows levels'
of familiar noises and gives human responses to such noises.
AN can be a source of annoyance to persons living near EHV
transmission lines.
Table 1.Examples of Environmental Noise Levels and Typical
Human Responses.(Source:EPA 1972)
Noise Level Human Conversational
(Decibels)Responses Relationships
150
Carrier Deck Jet Operation 140
Painfully Loud
lr-Contribution to hearing impairment begins.
The concept of "annoyance"in regards to wildlife is
not well defined..Stewart (1974)whose company manufactures
sonic animal repellent devices believed that humans and lower
animals have much in common regarding their responses to
noise.Consequently the widely use nAv-A1arm"sonic
generator successfully used in bird and mammal control work
was designed to produce the kinds of noise that promote
annoyance,nervousness,and discomfort in people (Stewart
1974).
One measure of the degree of human annoyance to trans-
mission line AN is the number of complaints a power company
receives.A guideline to the probability of receiving
complain ts abo lit AN \~aS developed by Perry (1972).{;Then
AN levels 30 m [rom the center of the right-of-way arc np-
proximately 53 dB(A)or lower no comp1ainst would be ex-
pected.AN above 59 dB(A)can result in numerous complaints.
Perry (1972)cautioned,that in practice the "acceptability"
of AN of various levels varies depending on such factors
as ambient noise,population density and level of 120 Hz
or other tones present in the AN.
Because of problems with audible noise BPA no longer
builds new 500-kV lines with a single subconductor per phase
and some lines of this type have been reconductored to the
newer three subconductor per phase design.
The subject of AN was one of the central issues in
extensive hearings held by the State of New York Public
Servic.e Commission for the purpose of certifying the
construction of 76S-kV transmission lines in that state.
The hearings began in 1974 and by June 1976 the testimony
of over 26 scientists and engineers had filled more than
10,000 pages (SYNPSC 1976).In addition to AN,testimony
was taken on ozone,induced electric shocks,and on the
b~ological effects of electric fields.
Jet Takeoff at 61 m
Discotheque
Auto Horn at .9 m
Riveting Machine
Jet Takeoff at 610 m
Garbage Truck
N.Y.Subway Station
Heavy Truck at 15 DI
Pneumatic Drill at 15 m
Alarm Clock
Freight Train at 15 m
Freeway Traffic at 15 m·
Air Conditioning Unit
at 6 m
Light Auto Traffic
at 30 III
Library
Soft Whisper at 4.6 m
Broadcasting Studio
130
120
110
100
90
80
70 11
60
50
40
30
20
10
o
Limit Amplified
Speech
Maximum Vocal Effort
Shouting in ear
Very Annoying
l~arlng Damage Shouting at .6 m
(8 hours)
Very Loud
Annoying Conversation at .6 m
Telephone Use LOud
Difficult Conversation at .6 m
Loud Conversation
Intrusive <It 1.2 m
Normal Conver~
Quiet sation at 3.7 m
Very Quiet
Just Audible
Threshold of Hearing
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH124
]I 1 j ,----]--.]1 ]J)
I 1 ]J 1 11
TRANSMISSION LINE AUDIBLE NOISE
I
125
The proposed 765-kVtransmission lines considered in
the hearings.would produce a maximum AN level less than 60
dB(A)at the edge of a 76 m wide right-of-way.Sleep in-
terference was the most serious possible effect predicted
for AN.Although the testimony in the hearings dealt pri-
marily with humans,at least two witnesses addressed pos-
sible effects on wildlife (Driscoll 1976,Fletcher 1976).
Fletcher (1976)suggested that AN from the proposed 765-kV
lines could at times mask certain acoustic signals that
could be critical to the survival of some animals.He added
that such effects on wildlife,however,would probably be in-
significant.Further,scientific evidence on which to base
those predictions were almost completely lacking according
to Fletcher.Driscoll (1975)believed AN could affect
wildlife breeding activities and predator-prey relationships.
He suggested the right-of-way may be less desirable to wild-
life during inclement weather because of high.levels of AN.
He also felt that little information was available to permit
quantitative assessment of the effects of AN on wildlife and
that research on the subject was needed.
One of the major difficulties in determining human
annoyance levels associated with AN is that annoyance is
dcternuned by n number of psychological factors.Anticaglia
(1970:2)pointed out that evaluation of noise by people in-
'volves both the consideration of the physical sound and the
subjective impression in the listener's mind.For example
any amount of AN may be extremely annoying to a person when
it is coming from a transmission line which was constructed
across his property against his wishes and only after a
lengthy condemnation proceeding.
Most of the literature dealing with the biologic ef-
fects of transmission line AN is oriented toward possible
effects on humans.In relating this literature to wildlife
,some distinctions should be made.One of the main dis-
tinctions is that AN as usually reported for transmission
lines is for locations at the edge of the right-of-way or
beyond.Easements purchased for rights-of-way are for the
purposes of operating and maintaining the transmission line
so persons who might find the higher AN levels on the right-
.of-way objectionable are not obliged to stay there.Wild-
life of course are not aware of the existence of legal right-
of-way boundaries.In considering the possible effects of
AN on wildlife it is therefore necessary to know the maximum
AN levels which occur on the right-of-way as well as levels
.at various lateral distances.As previously mentioned AN
levels can change significantly within short distance from
the line.
A related factor is that people are usually inside
closed buildings during inclement weather when a-c trans-
mission line AN is highest.Wildlife,however,may still
be moving about and have greater opportunity to encounter
the high levels of AN.Unfortunately,relatively little has
been reported in the literature about the effects of weather
on various wildlife species at different seasons of the year.
Spec:ies that become dormant during winter or that migrate
may encounter high levels of AN less frequently than resident
species.Rain,wind,and snow also adversely affect an ob-
server's ability to detect and study animals (Overton and
Davis 1969:425).
Another distinction is that AN measured in dB(A)may
not be the mos~appropriate measure of the noise as it is
perceived by wildlife.Although some species,including
most birds,have a hearing range which approximates that of
man other species may be sensitive to a much wider range of
frequencies.For a-c lines at least it is important to con-
sider the tonal component of the noise including frequencies
outside of those normally considered of importance to man.
Table 2 shows frequency hearing ranges of various
animals as compared with man.Many insects respond to
frequencies far above those audible to humans.The hearing
of most birds is similar to man and although many bird vo-
calizations contain ultrasonic frequencies birds probably
cannot hear such frequencies (Sales and Pye 1974).Mammals
respond to a wide range of frequencies including those
audible to man and those in the ultrasonic range.Tn rep-
tiles the importance of sOund perception is subordinate to
vision and chemorecept:i-on and sound producing mechanisms
are absent in most reptiles (Bogert 1960).
As mentioned previously corona can produce ultrasonic
frequencies.Weare not aware of any study in which ultra-
.sonic frequencies were measured in the corona noise produced
by a transmission line under normal 'operating conditions.
Ianna et al.(1973)studied the spectral characteristics of
corona produced by metallic protrusion on conductors in 11
laboratory.In one test with a voltage gradient on the
conductor of 13.3 kV/cm negative dc,the peak of the acoustic
spectra was between 24-26 kHz.
Although it "is reasonable to assume that transmission
line corona could produce ultrasonic frequencies which could
be heard by certain wildlife species,it is less likely that
such frequencies have any significant effe"ct except very near
the conductors.Ultrasonic frequencies are rapidly at-
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH126
1 j ]I 1 1 I L J )1 i J 1 J
TRANSMISSION LINE AUDIBLE NOISE 127
I
Table 2.Hearing Abilities (Frequencies)of Various Animals as
compared With ~~n.
Species
Lo.."r Maxlmum Upper
Limit Sensitivity Limit Source
(liz)(Hz)(Hz)Table 2.Hearing Abilities (Frequencies)of Various Animals as
Compared With Man.(cant.)
Source
Trainer (1946)
Schwartzkopff
(1955)
Ssles and Pye
(1974)
>8,000
18,000
150,000
Manunals
6,000
2,000-3,000
30,000-100,000
300
<1,000
<100
Species
Long eared owl
(~otus)
Mallard duck
(Ana!.~yrhynchos)
Lo ......er Maximum Upper
Limit Sensitivity Limit__---.,....Q!!L (Hz)(liz)
Bats
(Chiroptera)
EPA (1974)
Schaller and Timm
(1949,1950)cited
in Autrum (1963)
Roeder and Treat
(1957)
Haskell and Belton
(1956)
16 4,000 20,000
Invertebra.tes
3,000 --20,000
3,000 15,000-60,000 240,000
40,000-80,000
Noctuid moth i/
(Prodonia evldania)
Butterflies
(38 species)11
(Lepidoptera)
Man
(~sapiens)
Tiger moths 1/
(Arctlidae)-
Long-horned·
grasshoppers 1/
(Tenigoniidai)
Field cricket 1/
(Gryllus)-
Mosquitoe 2/
(Anopheles-subpictus )
800-1,000
300
150
10,000-60,000
380
90,000
8,000
550
Wever and Vernon
(1957)
Wever and Bray
(1933)
Tischner (1953),
cited in Autrum
(196)
Rodents
(Rodentia)
Cats
(Felidae)
Opossum
(Dide1phus virginians)
<1,000
<500
5,000-18,000,and
40,000-60,000 100,000
70,000
>60,000
Sal es and l)ye
(i974)
Evans (1968)cited
in SQles Qnd Pye
(1974)
Sales and (lye
(1974)
Male Midges 2/
(Tend ipedida;»
80-800 with
peaks at 125 and 250
Amphibians
Frings and
Frings (1959)1./Frequencies of continuous tones that stimulate the tympanal orgllllS.
2/Frequency'response of Johnston's Organ which .:Ire located at the b.:lse
-of the antcnmlf~.•
Crow
(Corv\,\s brachyrhrnchos)<)00
Kestrel (Sparrow Hawk)
(~.j>arverius)300
Bullfrog
(Rana catesbeiana)
Starling
(~vulgaris)
Hous~sparrow
(~dom~s ticus)
<10
<100
<1,800
Bi~
2,000
I,000-2,000
2,000
3,000-4,000 Strother (1959)
Granit (1941),
15,000 cited in Bremond
(1963)
Granit (1941),
18,000 cited in Bremond
(1963)
>8,000 Trainer (1946)
>10,000 Trainer (1946)
]I ]J J 1 _L]J 1 J J 1
126 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 129
tenuated especially by fog (Sales and Pye 1974).Those
authors also suggested that bats seem to avoid flying during
fog because these animals utilize ultrasonic echo location
for navigation.Atmospheric moisture,while causing'pro-
duction of corona and possibly ultrasonic frequencies,also
acts to decrease the propagation of these sounds.
Another point pertains to the ambient noise levels
with which transmission line AN levels are compared.Even
when considering the possible effects of AN on people the
significance of extremely low ambient levels as a basis for
comparison of the AN is sometimes overlooked.The range
.of environmental sound levels in the U.S.is very great.The
range of day-night (L dn )sound levels extend from the region
of 20-30 dB for wilderness areas to the region of 80-90 dB
or higher in noisy urban areas (EPA 1974).It should be
pointed out that even sounds in the natural environment can
reach high levels.Griffin (1976)measured sound levels near
a frog pond on a still night and found that steady frog
calling produced noise levels of 55-60 dB(A)with peaks to
75 dB(A).Waterfalls may produce noise levels of 85 dB(A)
or more (EPA 1974).
In contrast,on a number of occasions we have measured
sound levels as low as 15-20 dB(A)in contral Orogon in
places far from human development.At such low levels,one
strains to hear the slightest sound.Even light to moderate
levels of transmission line AN contrasted to these conditions
can be annoying.
Frings (1964)reported that in pest control applica-
tions the use of amplified communication signals as low as
3 dB above ambient can cause reactions in birds.l~en male
Japanese quail (Coturn~x japonica)were exposed for two
hours to white noise at levels of 12 dB(A)above ambient
the birds significantly increased the frequency of their
separation crowing (Potash 1972).Such a response to in-
creases in ambient noise may aid a separated pair of quail
in re-establishing contact.As Potash (1972)pointed out,
however,the increased chance of being detected by the pro-
spective receiver must be weighed against the chance of being
detected by a predator.In another case,Frings and Frings
(1959)found that small male flies (Pentaneura aspera)re-
sponded with an agitated circling and gathered around the
sound source when it was producing 125 Hz tones 13-18 dB
above ambient or 250 Hz at 3-8 dB above ambient.
The fact that noise from electrical devices can at-
tract insects has been noted by others (Sotavalta 1963:387).
This raises the possibility that although transmission line
AN may repel some species,it may attract others.Also,
insects attracted to the right-of-way could also influence
the ~ensity and distribution of insectivorous birds in the
vicinity of transmission lines.
Another point regarding distinctions between human and
animal responses to transmission line AN pertains to the
meaning of noise.As previously mentioned,noise is usually
defined as something unwanted.From the human viewpoint it
is difficult to imagine any positive effects of transmission
line AN.For wildlife,sounds from the inanimate environment
are potential carriers of useful information (Emlen 1960:xi).
For some kinds of wildlife the possibility exists that the
sound produced by a transmission line could act as a navi-
gational aid.Although this suggestion is highly speculative
at this time we feel it is worthy of consideration in light
of recent research.In one report,Griffin (1975)presented
evidence which suggested that on cloudy or foggy nights
migrating birds may obtain navigational information from
sounds characteristic of particular environments.Yodlowski
et a1.(1977)reported that homing pigeons can detect sound
energy be,low 10 lIz u t umpli tUUQS wJthln the rangl~a f those
occuring in the environment."Properly utilized,infru-
sound information could thus assist in almost every aspect
of avian navigation,in hoth homing and migration"(Yodlowski
et al.1977:226).Birds have been known to utilize trans-
mission line corridors as travel lanes (Carothers and Johnson
1975:215,Grue 1977:214).During inclement weather could
sounds produced by corona along a north-south run~ing trans-
mission line Similarly aid nocturnal ·avian migrants?
Before concluding our discussion of AN we would like to
mention one other topic which is important when considering
the possible effect of AN on wildlife.Throughout this paper
We stress that AN is only one component of a transmission
line environment.The effects of AN then must be'viewed in
relation to the overall effects of the line.The combined
effect of AN with effects from other transmission line par-
ameters could take several forms.Possibilities for com-
bined effects in such situations could be indifferent,ad-
dHive,synergistic,or ameliorative (EPA 1974:E-3).The
effect of relatively low level AN if it combined synergisti-
cally with the effect of another parameter could result in
a greater effect than if AN were considere~alone.Certain
chemical agents,and certain vibrations can have synger-
gistic effects when combined with noise (EPA 1974:E-5).In
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
j
130
J I
"
]1 I I I '1 -1 j
TRANSMISSION LINE AUDIBLE NOISE
')
131
bird control work (Busnel and Giban 1968)felt the addition
of a visual stimulus would enable lower sound intensities
to be used when using sonic repellents.In the transmission
line environment the effects of AN may combine with'the
electric and magnetic field synergistically.
THE EFFECTS OF TRANSMISSION LINES ON WILDLIFE
Although EHV transmission lines were first put into
operation in the 1950's.it was several years before any work
was dope to systematically document the effect of these lines
on wildlife.Passage of the "Environmental Policy Act of
1969"with its requirements that Federal agencies prepare
environmental impact statements for all major projects
pointed to the need for additional data for predicting en-
vironmental impacts.
One of the first attempts to assess the state of know-
ledge of the environmental impact of transmission lines was
a colloquium,"Biotic Management Along Power Transmission
Rights-of-Way"held at the University of Massachusetts in
June 1973 (Goodland 1973).Another contribution which
further defined the environmental impact of transmission
lines was published a year later by the Oak Ridge National
Laboratory (Kitchings et a1.,1974).The most recent
national event to provide a forum for discussing the impact
of transmission lines on wildlife was a symposium on "Enviro-
mental Concerns in Rights-of-l-lay Management",held in
January 1976 at Mississippi State University (Tillman 1976).
Biological Research on the BPA Transmission System
Having briefly described the transmission line enviro-
ment and potential sources of impact on wildlife we will now
describe BPA research conducted to date.This research has
provided information with which to begin assessing the pos-
sible effects of transmission line AN,and other parameters,
on wildlife.
BPA is a Federal agency responsible for marketing the
power generated by all Federal dams in the Columbia River
Basin.BPA transmission lines are located in a wide variety
of wildlife habitats including some of the most productive
big game habitat in the U.S.In 1974 BPA developed a pro-
gram to begin determining the effects of transmission lines
on wildlife •
Idaho SOO-kV a-c Transmission Line Study
The first research project developed in the BPA program
was designed to determine the effects of a SOO-kV trans-
mission line on migrating Rocky Mountain elk (Cervus canaden-
sis nelsoni)(Lee 1974).Concerns have been expressed that
transmission lines could interfere with movement of migratory
wildlife species (Villmo 1972.Martinka 1974,BPA 1974).
Villmo (1972:8)reported that the unusual noise generated by
power lines (no voltages or noise levels stated)seemed to
frighten reindeer in Scandinavia..He stated that "When
herders are attempting to move a reindeer herd across a power
line which is generating noise we know that the reindeer re-
act to the sound and are reluctant to pass under the lines"
(Villmo 1972:8).He also said that in soine caSeS it could
not be determined whether the power line itself or the
cleared right-of-way was alarming the reindeer.
BPA sponsored an intern with the Western Interstate
Commission for Higher Education (WICHE)to'conduct a I-year
study of the possible effects of a transmissiuon line on
elk migration.The study was completed in June 1975 and was
one of the first studies to systematically investigate and
document wildlife behavior near a 500-kV line (Goodwin 1975,
Goodwin and Lee 1975).
The study was designed to test the hypothesis that elk
movement on,and use ofa 500-kV transmission right-of-way,
is no different than that occurring on other forest
clearings.The study area was in northern Idaho along the
BPA 500-kV line between Dworshak Dam and Hot Springs,Mon-
tana (Figure 1).The line is located in heavily 'forested
areas of the western red cedar (Thuja plicata)/western
hemlock (Tsuga heterophylla)vegetation type.
Construction of the Hot Springs-Dworshak line began
in July 1968 and was completed in October 1972.The line
was engerized in March 1973.Voltage extremes on the line
range from 500-550 kV.The steel.delta configuration towers
average 37 m in height and are spaced approximately three per
km.Three subconductor configurations are used on the line;
the single,double and triple subconductor per phase forms.
Audible noise characteristics for these configurations vary
considerably (Figure 4).
The study was based on a comparison of animal move-
ment on and use of the right-of-way with that on other
clearings.Five paired right-of-way and control areas were
used during the study.Study methods include4 direct ob-
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
I
132
J j ---1 ---I J 1 J
,
I I I I J
TRANSMISSION LINE AUDIBLE NOISE 133
servations,time lapse photography,track counts,and vege-
tation analyses.In addition to elk,the study provided in-
formation on several other ,wildlife species,and on the use
of the right-of-way by hunters.I
When an animal was observed in the right-of-way or con-
trol,an audible noise measurement in dB(A)was made under
the outer conductor and the noise level at the animal's loca-
tion was estimated.Estimates were made based on the know-
ledge that line noise attenuates at a rate of 3 to 4 dB for
each doubling of distance (Perry 1972).Noise measurements
were made with a General Radio Type 1551-C sound'level meter.
The 25 mm ceramic microphone was approximately .5 m above
the ground when measurements were made.No measurements of
the 120 Hz hum or other frequencies were made.
Between August and December 1974 a total of 310 hours
was spent observing two paired right-of-way and control
areas.Due to minimal use which the study areas received
during this time of year and the nocturnal behavior of many
animals,very few observations were made.Pnly 4 deer,2
bear (Ursus americanus),6 elk,and 22 coyotes (Canis lat-
rans)were-observed.From March to May 1975 less emphasis
waS pl.:lced on di.rect obscrv.'ltions,however,several hundred
deer and elk were seen while the observer ,,,as counting traeks
and servicing time lapse CLllneras.The problems which 11011 t<..~d
the direct observations in the fall also applied to the
time lapse cameras.
Typical behavior of most deer and elk when they entered
the right-of-way or control was to remain motionless for a
few moments at the forest edge.After this,they entered the
clearing and usually began feeding.After initial wariness
when entering a clearing none of the deer or elk observed
appeared to be disturbed by the presence of the transmission
line.
Results of the track counts indicated deer and elk
movement across all forest openings during the fall was low.
but increased steadily throughout the season.Elk move-
ment particularly increased once snow began to accumulate.
The tracks of 87 elk and 9 deer in the vicinity of the right-
of-way were followed in the snow.Thirty-eight percent of
the animals maintained a relatively straight line of travel
as they approached,crossed,and left the right-of-way.
Sixty percent of the animals followed roads or established
game trails in crossing the right-of-way.Only 2 percent
failed to cross the right-of-way.In these two cases elk
ca,me within 25 m of the right-of-way and appeared to have
come to the area to feed.
Generally the right-of-way and control areas had
significantly greater ground cover than the adjoining areas.
The percentage of grasses,forbs,and shrubs sometimes dif-
fered considerably between right-of-way and control.
Fair weather AN on the right-of-way for the singl~con-
ductor per phase configuration ranged from 45 to 55 dB(A).
I.evela of 62-68 dB(A)were measured during rain.For the two
conductor per phase configuration,maximum fair weather AN
was 35 to 40 dB(A).AN from the three conductor per phase
configuration was usually less than 30 dB(A).A reading of
52 dB(A)was recorded on the right-of-way during a light
shower.AN measured in the control areas was usually below
30 dB(A).The highest reading in a control area was 44 dB(A)
whtch was during a light rain.
During several days of 55 to 60 dB(A)noise levels,
deer and elk track counts did not indicate any aversion by
the animals to the right-of-way.The study was not specifi-
cally designed to provide quantitative data on the possible
effects of the line on birds,however,ravens,grouse,and
several other bird species were observed near the line when
noise levels exceeded 60 JU(A).During the study a hurd DE
approximately 60,bighorn sheep was observed In the Dlvorshak-
Hot Springs SOO-kV right-of-way near lIot Springs,Hontana.
During a light rain with AN of 53 dB(A)the sheep Were ob-
served bedded down on the right-of-way.
The activity of hunters on the right-of-way and aCcess
roads had a significant influence on elk movement:Although
segments of the right-of-way were closed by locked gates,
some hunters broke the gates in order to drive onto the
right-of-way.Many persons hunted the right-of-way on foot
and some used motorcycles.Hunting pressures had a definite
effect on elk distribution.Elk moved away from hunting
pressure and concentrated in places 0.8 km or more away from
roads and clearings.
Data obtained during the Idaho study indicated that
elk movement near the 500-kV transmission line right-of-way
was not significantly different than that near other forest
openings.The transmission line produced audible noise
levels which at times were very,annoying to humans.There
was no indication,however,that the noise deterred elk,deer
and several other wildlife species from entering and crossing
the right-of-way.Elk and deer USe of the'right-of-way and
control areaS WaS primarily a function of avai~able forage.
TRANSMISSION LINE AUDIBLE NOiSe
I
134
i
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
j 1 J l J )~~l ~I I j I
135
Elk and deer avoided the right-of-way and control clearings
during the hunting season.The transmission line.however.
did not appear to prevent these animals from eventu&lly
crossing the right-of-way and continuing their migration.
1100/1200-kV Transmission Study
In April 1976 another BPA-sponsored biological study
began.This one is being conducted at the site of the BPA
1100/1200-kV prototype transmission line near Lyons,Oregon
(Figure 6).This 31-month long study is being conducted by
Battelle-Northwest of Richland,Washington.
During the Environmental Impact Statement process for
the 1100/1200-kV project,questions were raised as to the
possible biologic effects of such a line (BPA 1976b).No
significant adverse biologic effects are expected.However,
,because of the concerns which We~e raised,and because few
scientific studies have been conducted for existing trans-
mission lines.BPA decided biological studies would be an
integral part of the prototype project.
Construction of the 2.1 km long line began in the
spring of 1976 and was completed the following fall.The
line was constructed on a right-of-way which had contained
three 230-kV transmission lines.One of the 230-kV lines
was removed and the 1100/1200-kV was constructed in its
place and relatively little tree clearing was required.The
first of three transformers was energized December 21,1976.
All three phases were energized on Hay 10,1977.
The prototype line is providing a source of data for
evaluating the steady-state electrical effects of 1100/1200-
kV including AN.radio and television interference,electro-
static effects,and effects on other utilities.
Transmission lines of 1100/l200-kV can be designed so
electrical effects (i.e.,maximum ground level electric
field strength.AN,and oxidant production)are not signi-
ficantly different from 500-kV lines.This requires the
use of towers averaging 61 m in height and 8 sub conductors
for each phase.Each sub conductor is 4.1 cm in diameter.A
lateral profile of AN calculated for the 1100/1200 kV line
is shown in Figure 7.The prototype line has been designed
so that in two locations within a fenced study area,electric
field strength could approach 14 kV!m.Other than possible
damage to some trees which have purposely been left quite
near the line,these higher field strengths are not expected
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136
J 1 C-~l ]11
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
1 1
J I 1 II 11
TRANSMISSION LINE AUDIBLE NOISE
1
137
Figure 7 -Lateral profile for calculated mean audible noise
for the B.P.A.1100/1200 kV Prototype Transmission
Line \".,ith eight 4.1 cm diameter conductors per
phase.Adapted from Biological Studies Task Team
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to result in any adverse biologic effects.By using these
higher levels,however,the potential for threshold effects
occuring just above design limits of 9 kV/m can be evalua-
ted.
Biological studies at the 1100/1200-kV site include
natural vegetation,crops,wildlife,cattle,and honey bees
(Lee and Rogers 1976).From April to December 1976 pre-
energization biological data was obtained with which to
identify possible effects occurring after engerization.
The general study approach after energization is to compare
plants and animals on the llOO/1200-kV right-of-way with
those in nearby control areas.
Total abundance and species diversity are the two
main parameters which will be used to evaluate possible ef-
fects on bird populations.Observat~ons of flight and
feeding behavior will also be made.Birds inhabiting the
study area are sampled along transects in four areas con-
sisting of two treatments (right-of-way)and two controls
(Figure 6).Birds 'seen,or heard within a radius of 20 m
are counted during early morning surveys on three consecu-
tive days.
Two hundred small mammal live traps are located along
the same transects used for the bird studies.The traps
are set for three consecutive nights and captured animals
are marked with a unique toe clip pattern.Information on
weight,approximate age,and reproductive condition is re-
corded each time an animal is captured.
Honey bees are being used as an indicator 'species to
evaluate possible effects on insects.Honey bee studies
take place during the spring and summer of 1977 and 1978.
Six colonies are placed beneath the 1100/1200-kV line,and
six away from the line (Figure 6).Parameters selected for
study are honey and wax production,mortality,swarming
tendencies,foraging,and general behavior.This phase of
the study will complement a similar honey bee study spon-
sored by the Electric Power Research Institute (EPRI)which
is being conducted beneath a 765-kV transmission line
(Kornberg 1976).
Results of the biological studies,along with results
of economic and engineering studies will provide the basis
for a decision on whether to adopt 1100/1200-kV transmission
in the BPA system.At the time this paper was written only
a small amount of post energization biological data had been
collected at the 1100/1200-kV test site.
138
1--1 11 --1
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
)J r J 1 I ~--~J ---].1 I 1 ]
TRANSMISSION LINE AUDIBLE NOISE
]
139
Preliminary analysis of pre-energization bird data
shows that although more birds were observed in the control
areas than in the treatment areas,the differences were not
statistically significant (Rogers 1977).Analysis of post-
energization bird and mammal data will be done when suffi-
cient data has been accumulated.No obvious adverse effects
on bird and mammal populations have as yet been identified
which could be attributed to AN or other operational para-
meters of the 1100/1200-kV line.During this time maximum
line voltage was 1100 kV.Beginning in the summer of 1977
the line will be operated at 1200 kV during certain inter-
vals.Preliminary measurements made since energization of
the three phase 1100/1200 kV prototype line indicate the
amount of AN produced by the line is within .±2 dB of the
calculated values shown in Figure 7.
Although very little foul weather AN data has as yet
been obtained for the 1100/1200 kV line,preliminary measure-
ments point out again that line design e.g.,number and
diameter of conductors.and not iust line voltage alone
determines the AN characteristics of a transmission line.
Only on a few occasions have behavioral responses been
observed in animals which appeared to be a response to the
electrical parameters of the 1100/1200-kV line.Shortly
after the first phase of the line was engerized an American
kestrel (Falco sparverius)attempted to land on an energized
conductor.The bird approached to within approximately 30
em of the conductor and after a few attempts at landing it
finally fIe,v off.The bird later landed on One of the un-
energized phases of the 1100/1200-kV line.When all three
phases of the 1100/1200 kV line were first energized the five
head of cattle in the test pen were lying down almost direct-
ly under the line.When the line was energized there was a
moderate amount of AN and four of the cattle immediately rose
to their feet.After a few minutes two of the cattle laid
down again near the line and the others began grazing near-
by (John Hedlund,personal communication).
No behav:ior~l effects have been noted in the honey bee
colonies under the 1100/1200 kV line which could be attri-
buted to operation of the line.
More data will be required to properly assess the pos-
sible biologic effects of the 1100/1200 kV line.Bio-
logical studies at the prototype site will continue through
August 1978.
HVDC Transmission Line Biological Study
Relatively few d-c transmission lines have been con-
structed throughout the world.One of the first and longest
d-c lines built is the Celilo-Sylmar .±400 kV d-c line which
extends from The Dalles,Oregon to Los Angeles,California
(Figure 1).A literature review failed to identify any
biological studies which had been conducted on a d-c trans-
mission line right-of-way.With planning underway for a
possible second d-c intertie line,BPA developed a program
to study the effects of the existing Celilo-Sylmar d-c line
(BSTT 1976).A l3-month long study began in June 1976.The
BPA sponsored study is being conducted by the junior author.
The d-c biological study includes natural vegetation,crops,
wildlife,and domestic animals..
Although at various times observations were made along
the entire Oregon portion of the d-c line,two primary areas
were selected for intensive study.One was located in the
Western juniper (Juniperus occidentalis)vegetation zone and
the other in the big sagebrush (Artemisia tridentata)zone.
Almost 90 percent of the Celilo-Sylmar d-c line in Oregon is
located within these zones.Field studies were conducted
from mid-June 1976 through January 1977,and from May through
mid-June 1977.Because data analysis was not complete as
this paper was written only preliminary results arc presented
here.We feel this is warranted because to our knowledge this
was the first biological study of a d-c transmission line
conducted in the U.S.,and the measurements of AN made during
the study are among the first to be reported for the Celilo-
Sylmar d-c line which were made over an extended p~riod of
time.
Power is transmitted on the Celilo-Sylmar +400-kV d-c
transmission line via a negative and positive p;le each of
which consists of two 4.56 em diameter subconductors.The
.subconductors are strung on steel self-supporting or guyed
aluminum towers which arc typically 36 m tall and 12 m wide
at the crossarms.Ground clearance to the conductors varies
from approximately 25 ,Ill at the towers to approximately 13 m
.at midspan depending on site characteristics.Tower spacing
averages 2.9/km.A single overhead ground wire runs the
length of the Oregon portion of the d-c line.A light duty
maintenance road parallels the line approximately 15 m from
the center of the right-of-way •.Distribution of ground level
electric field strengths for the d-c line is generally as-
symetrical and varies widely due to the pronounced effect of
wind on space change distribution (Bracken et al.,1977).At
no time during the study did we notice any effects which in-
1.40
]II
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
1 1 ".1 J 1 '~I
TRANSMISSION LINE AUDIBLE NOISE
J
141
dicated we could perceive the d-c fields.
Relatively few AN measurements had been made for the
Celilo-Sylmar d-c line when this study was initiated although
AN was measured during studies conducted with the d-c test
line at The Dalles,Oregon (Hill et al.,1977).At various
times during this study measurements of AN were made on the
right-of-way and in control areas.These were made with a
Bruel and Kjaer Type 2204 sound level meter with a 25.4 mm
condenser microphone.With this microphone the meter had a
range of 15-140 dB(A).The meter was fitted with an octave
filter set with 10 center frequencies from 31.5 H~to l6000
Hz.All measurements were made with the meter mounted on
a tripod with the microphone in a vertical direction (per-
pendicular to the conductors).The microphone was covered
with a polyurethane sponge windscreen when measurements were
made.AN levels measured on the d-c transmission line right-
of-way were generally lower and more variable than that re-
ported for a-c lines of comparable voltage.Increases in
AN above ambient for the d-c line ranged from essentially
o up to 20 dB(A)with most measurements in the 0-10 dB(A)
range.The highest AN level measured on the d-c line right-
of-way during the study was 38 dB(A)which is probably about
the maximum expected.
For wildlife studies emphasis was on songbirds,raptors,
small mammals,mule deer (Odocoileus hemionus),and pronghorn
antelope (Antilocapra americana).For purposes of this
paper,only preliminary data from the songbird studies will
be considered in detail.Songbirds were sampled using a
circular plot technique.All birds seen and heard from fixed
points were counted during early morning hours at 0.4 km
intervals along 3.6 km long transects.The distances of the
birds from the observer were measured with a rangefinder which
had an upper limit of 219 m.Distances to birds further than
this were estimated.In addition,the position of each bird
was noted as being in one of eight 45 degree sections centered
on the observer.During the 1977 spring sampling period this
method was modified.A bearing was taken on each bird so
that the distance of each bird from the center of the d-c line
right-of-way could be estimated.In addition the length of
the transects in the sagebrush study area was lengthened to
5.6 km with 15 stations.In the sagebrush study area,one
transect was located on the center of the d-c line right-of-
way and another in a control area parallel to the right-of-way
and approximately 800 m away.In the Western juniper study
area,a transect was established along a road which paralleled
the right-of-way and was 400 m away.This was in additi.on
to the right-of-way and control transects.In each study
area songbird sampling was conducted on alternate days until
a total of four days was completed for each transect for each
of three sampling peri.ods.
During the 1976 songbi!d sampling period,a possible
sampling bias introduced by the effects of transmission line
AN on the observer was identified.Subjectively,it seemed
that AN of certain levels and quality might function to:
(1)increase the ambiguity of species identification,(2)
lnask detectability of bird calls,or (3)bias distance esti-
mation to those birds which were only heard.Since 50-80
percent of birds detected on right-of-way and control tran-
sects were heard but not seen these sources of bias cCiuld
affect the indices to songbird abundance and distribution
obtained from the censuses.
Sagebrush habitat,where transmission line construction
effects on vegetative structure are the least obvious,pre-
sent the best field situation for examining the possible
sources and magnitude of these biases.Even so there were
differences in vegetation on the right-of-way compared with
the control areas.In the control as compared to the right-
of-way,big sagebrush occurred with slightly greater fre-
quency,and the mean height and percent of total cover was
slightly ,greater.On the right-of-way green rabbit brush
(Chrysothamnus nauseosus)and grasses accounted for a signi-
ficantly greater'(P <a .05)proportion of total cover than on
the control.
In 1976 and 1977 the total number of birds detected on
the right-of-way transects was respectively 76.2 percent and
75.2 percent of the total number detected on the control
transects.Unknown species of birds 'were not counted during
1976.In 1977 unkown species accounted for 13.7 percent of
the total number of birds detected on the right-of-way
transects and 12.4 percent of the total number of birds de-
tected on the control transects.This difference of 1.3
percent was not statistically significant at the 0.05 pro-
bability level.
In 1977 the distances to birds heard but not seen were
classed as close,medium or far.These classes corresponded
to distances of less than 100 m,100-200 m,and greater than
200 m,respectively.The four most abundant species of
songbirds were tabulated,considering only those birds heard,
into these classes (Table 4).The species were arranged in
a subjective ranking of song volume with the sage thrasher
the loudest and the horned lark the quietest.
~
1 )1 1 ---1 )J .,1 1 I 1 j 1 1 )
142 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 143
Table 4.Percentage Distance Distribution of Birds Heard
Only,On Control and Right-of-Way (ROW)Transects
in Sagebrush Habitat Along the ±400 kV d-c Trans-
mission Line in Central Oregon /
Distance
Close 1/Medium 1/Far]/
Species Transect
Sage Thrasher Control 16.8 57.1 '26.1
(Oreo s cop te s ROW 1lI.4 57.7 27.8
montanus)
Sage Sparrow Control 42.9 55.7 1.4
(Amphispiza ROW .35.4 60.8 3.8
belli)
Brewer's Sparrow Control 72 .3 27.7 0.0
(Spizella breweri)ROH 61.1 38.9 0.0
Horned Lark Control 87.0 13.0 0.0
(Eremophila ROW 91.7 8.3 0.0
alpcstris)
1/Less than 100 m
2/100-200 m
"jj Greater than 200 m
There was little difference between right-of-way and
control distributions (Table 4)for the loud sage thrasher.
For the sage sparrow and Brewer's sparrow respectively,ap·
proximately 5 percent and 11 percent more birds were classed
in the medium distance category for the right-of-way transects
compared to the control.This could indicate that AN from
the transmission line was biasing distance estimates.
Analysis of the distance distribution from the transect
centerlines for birds seen,however,showed that the mean
distance was slightly greater,though not statistically
significant,for both sage sparrows and Brewer's sparrows
on the right-of-way compared to the control.The increased
frequency of these birds in medium and far categories may
reflect actual distribution patterns rather than AN bias on
the observer.
Horned larks present a somewhat different case.Their
call and song is weak in comparison to the other birds in
Table 4.It seems that the approximately 5 percent lower
frequency of horned larks classed in the medium distance
category on the right-of-way ,may reflect masking of this
species'call by certain levels and quantities of AN from
the transmission line.
If the AN from the transmission line markedly affected
the total number of birds detected on the right-of-way we
might expect the percent of total birds that are heard but
not seen to be greater on the control transects as compared
to the right-of-way.Some ambiguity in this relationship
might be introduced by the fact that a number of the birds
seen are first detected by auditory means.
In 1976,79.9 percent of the total birds detected on
I the right-of-way were heard only and 71.5 percent of the
total birds detected on the control transects were heard only.
In 1977,67.0 percent of birds detected on the right-of-way
transects were heard only and 67.6 percent of birds detected
on the control transects were heard only.In neither year
was the difference between percent heard only on right-of-way
and control transects significantly different.
The bias of AN on songbird detection on the +400 kV
d-c transmission line'right-of-way docs not then ~ppcar to
be of great enough magnitude to account for the approximately
25 percent lower munber of birds detected on the right-of-way
transects.Positive identification of this bias may have been
obscured by the variable character of the AN from the d-c
line.At each right-of-way transect station in 1977 the AN
from the d-c line was classed into one'of four categories:
(1)no line AN perceived,(2)line AN perceived but of minor
interference in songbird detection,(3)line AN perceived
and of moderate interference in songbird detection,and (4)
line AN perceived and of major interference in songbird de-
tection.For the 60 transect stations (4 daily transects
with 15 stations each day)the distribution of the AN into
the above four subjective categories was:
category 1,17 stations
category 2,12 stations
category 3,17 stations
category 4,14·stations
We feel that AN bias becomes a more important consider-
ation at higher transmission line AN levels 'than measured for
the d-c line.The bias may be more subject to identification
on a-c lines where AN is of generally higher 1eye1s and
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH144
J f J 1 T11J j 1 1 1 I Ji I j
TRANSMISSION LINE AUDIBLE NOISE 145
j
Wildlife Observations Near Two 500-kV Transmission Lines
As described above,during the study of the d-c trans-
mission line we identified possible effects of AN that may
affect an observer's ability to detect songbirds on the right-
of-,.,ay.The possibility that AN may also affect songbird dis-
tribution was also raised.
To obtain additional information on these possibilities,
the senior author made observations along the right-of-way
of two 500-kV a-c transmission lines in south cennal Oregon.
These lines,Grizzly-Malin,run generally north and south and
in places are near to the Celilo-Sylmar d-c line (Figure 1).
These lines were constructed and energized during the late
1960's.The lines consist of steel lIdeltall towers and
'each phase is strung with two 4.07 cm diameter subconductors.
Both lines have two overhead ground wires for lightning pro-
tection.An access road runs between the two lines.The
two parallel sets of towers are approximately 50 m apart.
The observation period (June 5-June 8,1977)was timed
to coincide with similar field observations being conducted
on the d-c line.Two 3.6 km long sample transects were es-
tablished.One was along the center of the right-of-way and
the other was 525 m west and parallel to the lines.The
study area was approximately 129 km south of Grizzly Sub-
station (Figure 1).Topography of the study area waS fairly
level and was in the big sagebrush vegetation type.We
chose the particular site because it was one of the few areas
along the right-of-way located completely in sagebrush.We
felt that the pOSSible effects of AN would be more apparent
in such an area where relatively little difference in vegeta-
tion existed between the right-of-way and adjacent areas.
Sample methods employed were similar to those utilized
in the d-c transmission study.In addition to birds counted
at 10 stops along the transects,birds seen and heard be-
tween stops were also counted.The stops provided an op-
portunity to observe bird behavior under differing AN levels.
The location of each bird seen or heard was recorded by
noting both the angle and distance of the bird from the ob-
server.A range finder with an upper limit of 180 m was
used to measure distances.A metal plate marked in degrees
and fitted to a tripod on which was mounted a lOx spotting
scope was used to determine bearings.
Counts began within one-half hour after sunrise.One
transect was usually completed by about 0900 hours and then
counts were made on the other tranSect while returning to
the starting point.The second tran~ect was usually com-
pleted by about noon.Counts were conducted on four con-
secutive days beginning June 5.The transects were alter-
nated so that two early and ,two late morning counts Were con-
ducted for each transect.
AN measurements were made each day at about sunrise
before the counts began and then again after both transects
had been con~leted.At both times measurements were made on
and off the right-of-way.Measurements were made with the
Bruel and Kjaer type 2204 sound level meter which was de-
scribed above.The meter was tripod mounted which put the
microphone about 1.5 m above the gound plane.Measurements
on the right-of~way were all made at the same point which
was mid span between two particular towers.The meter was
placed directly under conductors and the distance from the
microphone to the conductors was 11 m.
Figure 8 shows how AN levels varied between the right-of-
way and in the control area during the sample period.During
fair weather AN measured on the right-of-way averaged ap-
proximately 15 dB(A)higher than in the control area.With
wet conductors there Was about a 20 dB(A)difference between
the twO areas.The levels arc for Periods of m1.nimal wind
and/or bird calls.We feel this best depicts the AN produced
by the lines in comparison to the relutively quiet sur-
roundings of the study area.Wind or birds would at times
produce sound level meter readings in the control area which
equaled or exceeded readings on the right-of-way.
Although most AN measurements were made only on the
right-of-way or in the control area,on the night of June 4
measurements were made at two lateral distances near the
500-kV lines.With AN on the right-of-way at 46 dB(A)and
19 dB(A)in the control,40 dB(A)was measured 25 m west of
~he outermost conductors,and 36 dB(A)at 50 m.
During the sample period the 500-kV lines were always
audible on the right-of-way transect and frequently from the
control even during fair weather.This is in contrast to the
more intermittent AN from the d-c line.
Although some birds were detected at distances up to
200 m or more from the center of the right-of-way,AN from
the two 500-kV lines was sufficiently loud to cause some
ambiguity in the ability of the observer to detect birds by
their calls.The problems did not appear to be so much re-
~-·-1 1 j )J ..,J I I I i i I 1 1
146 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 147
In an attempt to eliminate some of the bias caused by
the AN,we have tabulated only birds seen and heard within
75 m on either side of the right-of-way.'In the field,it
appeared the AN was not significantly affecting the observers
ability to detect birds within this distance.Figure 9 shows
the distribution of birds seen and heard during the four
sample days within the 150 m wide transect on the right-of-
way and in the same size transect in the control.As
determined by a t-test for two sample means there was no
significant difference in the mean distance of detected birds
from the center of the right-of-way transect compared with
the control.The relatively high number of birds detected
near the center of the tranSects is in part due to birds
being flushed by the'qbserver.
lated to hearing and locating birds by their songs but short,
weak calls (e.g.,cheeps,tweets)were sometimes difficult
to locate when AN was originating from lines on either side
of the observer.This effect,first noted on the d-c line,
was more apparent with higher AN of the a-c lines.
Another explanation for the large number of birds ob-
served in the center of the right-of-way may be possible
effects of the access road.Birds along the road may have
been more easily detected visually.On several occasioQs
birds appeared to be attracted to the edge of the road.Even
though the road was only 6 m wide the "edge effect"may have
been a factor contributing to the greater number of birds
near the center of the right-of-way.Additional information
to evaluate this possibility could be obtained by conducting
a count along a road near the transmission line which is of
a similar width and which receives similar travel as the
right-of-way,During the study period no vehicles were Seen
using the access road.On the weekend prior to the study a
number of motorcyclists were observed using the access road
and other roads in the area.
Although the detected birds appeared to be similarly
distributed within the two transects,there was a 'statis-
tically significant difference (P(O.05)in the total number
of birds detected in the two areas.Table 5 gives the
total birds detected on each day for both seen and heard
birds.Table 6 lists the bird species counted.
/
...
0430
to
0505
KEY
"A"Weighted,Control (Am-bient.fair weath;r)
"A"Weighted,500 kV Lines I [~t:~1H I I
125 Hz,Control (Ambient,fair weather)
125 Hz.500 kV Lines
.Ambient lOuring Rain)
June 4
65
60
45 I ~I I I
30
25
20
10
Figure 8 -Audible noise measured during June 1977 on the
.right-of-way of two 500 kV a-c transmission lines
(Grizzly-Malin)as compared with a control area
525 m away from the line.During rain ambient
noise was also measured 1.6 km away from the line.
~For the times shown above each day,the dB value
at the top of each keyed bar pattern represents
the average noise level measured during an approxi-
mate 3 minute period with essentually no wind.The
line voltage during the measurement period is shown
~"~~r~~A~~n kV.
50 I I I I l~~
551 I I I ~
35
~40 I I;'>~~I
70 I •••I I
15
~~-1l•1
<f--1 I j 1 I I f j
148 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 149
0)10313050818
a
C")
a
'"~a a
C")
03l:J3130 50818
a aN~o
Figure 9 -Counts were made June 5-8,1977 in south central
(continued)Oregon in Big Sagebrush (Artemisia tridentata)
vegetation type.
1/These counts are for the early morning sample which began
one half hour after sunrise.The other counts were then
conducted from about 0900-1200 hours.
Table 5.The total number of birds seen and heard only,a-
long 3.6 km long,150 m wide transects during
morning counts from June 5-8,1977.One transect
was on the right-of-way of two 500-kV transmission
lines and the other was parallel to the lines and
525 m away.
24
LIO Y
33 1/
28
125
6
8
5
30
11
Right-of-way Transect
22
25
19
29
95
45 1/
51
63 Y
39
198
2
77
23
32
20
Control Transect
Birds Birds
Seen Heard only Total Seen Heard only Total
Day
June 5 43
June 6 28
June 7 31
Totals 121
June 8 19
oN W
Uz
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M '£!o
-'<!
o a:<t W·
':i-'
o....
o...
~
o
'"
~
V>a:
woI-.,.w
~
I-
o U
C")wV>
Z
<!a:
o l-
N -'oa:
I-o Z~0u
W-o
o a:
w
I-
Z
W
~u
:<
.0a:
""
a
"
o...
o
'"
o
"
o Vi...a:w
I-w
o ~
M >-«~
o u:-
N 0..:.
:I:
~
o a:
w-o
a:
o ~z
Wu
o ::;:~0a:
""W
o U
N Z
<!
I-
Vl
o 0
M -'
<{
a:w
o I-<t <(
..J
o
In
o
'"
a....
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Vl
<(
W
l-V>w
$:
~
~
o
C")
o
N ;?o o
C")
o
N ~o
03.103130 50818 03.103l30 50818
Figure 9 -Distribution of birds seen and heard during morning
counts along alSO m wide,3.6 km long transect
along the right-of-way of two 500 kV transmission
lines and along a similar size control transect
~~~~11~1 rA thA ri~ht-nf-WRV and 525 m west.
TRANSMISSION LINE AUDIBLE NOISE150
J I ')1
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
'I'j j )J I I J j 1
151
Species distribution of birds seen and heard albng
3.6 km long,150 m wide transects during morning
counts from June 5-8,1977.One transect was on
the right-of-way of two 500-kV transmission lines
and the other was parallel to the lines and 525 m
at~ay .
Control Righ t:-of-\Vi'!Y_
Table 6.
Species 1./
Brewer's Sparrow
(S~izella breweri)
Sage thrasher
(Oreoscoptes
montanus)
Sage sparrow
(Amphispiza
belli)
Number
Detected
97
15
18
Percent of
Total
49
7.6
9.1
Number
Detected
46
18
19
Percent of
Total
36
14.4
15.2
Of particular interest in relation to AN bias is the
ratio of birds that were heard only to the number seen which
were not heard first.For the control transect this heard/
seen ratio was 0.64 compared to 0.32 for the right-of-way.
This indicates a noticeably ,greater proportion of auditory
detections on the control transect.In addition,many birds
that are eventually seen are first heard.AN then,may also
bias,visual detections as well.On the control transect
44 percent of the birds seen were heard'first and on the
right-of-way the corresponding percentage was 35.
Assuming the AN did bias bird detectability,heard/seen
ratios and the percent of seen birds that were heard first on
the control,can be used to derive an estimate of the degree
of bias present.We have calculated that in the present
example,the bias introduced by AN could account for as much
as 75 percent of the difference in total birds detected be-
tween the right-of-way and control transects.These cal-
culations were based on the number of birds seen and not
heard first on each transect.For these birds that were seen
only,there was only 9 percent fewer detected in the right-
of-way as compared to the control.
1/The right-of-way also contained a raven nest with four
young on a tower.
1/Most of the birds in this category were probably either
Brewer's sparrows or Sage sparrows.
Total 198 125
Horned lark 6
(Eremophila
alpestris)
Headow lark 0
(Sturnella
lleglecta)
Loggerhead shrike 0
(Lanius 1udovicianus)
American kestrel 0
(Falco sparverius)
Mourning dove 0
(Zena~dura ~acroura)
Unknown 1/61
3
o
o
o
o
30.8
o
1
4
2
2
34
o
0.8
3.2
1.5
1.5
27.2
The magnitude of this bias would most likely vary among
sped,es due to differences in song volume and calling rates.
The above calculations assume the same rate and intensity
of bird vocalizations between the right-of-way and the con-
trol.AN could cause an increase in the frequency of calling
rates similar to that reported by Potash (1972).This could
function to lower the percentage of the difference in birds
detected between right-of-way and control which co~ld be
accounted for by the AN bias.
Vegetation differences could in part be responsible for
the remainder of the observed differences between right-of-
way and control transects.Vegetation composition and dis-
tribution has consistently been shown to be an important
factor which influences bird distribu'tion (Tomoff 1974,Ba1da
1975).Although no quantitative measurements of vegetation
on the right-of-way and control transects were made,in
general the shrub density appeared to be very similar be-
tween the two areas.Noticeable exceptions included the
bare.unsurfaced access road (approximately 6 m wide)on
the right-of-way and areas near some towers which had ap-
parently not completely revegetated since construction.This
reduction in shrubs available for singing perches and feeding
areas could cause some reduction in density:
-c-C::l -)--I J
1 -J I 1 ]I J .fi
~I
152 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 153
Grue (1977:130)believed that removal of nesting and
foraging habitat was a primary factor responsible for lower
densities of breeding birds on the right-of-way of two 500-
kV transmission lines in the desert shrub habitat in Arizona.
Grue also counted birds heard and seen during his study
although he did not believe AN from the lines biased his
ability to detect birds by sound (Grue,personal communica-
tion).
Another possibility for the lower densities is that the
transmission line itself including the electric field and/or
audible noise caused some birds to avoid the right-oi-way.
Grue (1977)also suggested that these factors were at times
responsible for lower bird densities on the right-oi-way of
two 500-kV lines in Arizona.On numerous occasions during
the census counts,birds were observed perched and singing
directly under the conductors during conditions of highly
noticeable AN.Several other birds were observed flying
across the right-of-way near the conductors.No unusual
animal behavior was observed which obviously suggested an
aversion to the right-of-way by birds which could be dir-
ectly attributed to the AN or the electric field of the
500-kV lines.
An afternoon thunderstorm on June 7 provided an opportu-
nity to make additional observations during a period when
high levels of AN were being produced by the lines (Figure 8).
Shortly after the rain began observations were made along
the portion of the right-of-way containing the census tran-
sect.A golden eagle (Aquila chrysaetos)and a red-tailed
hawk (Buteo iamaicensis)were observed perched on towers.The
birds appeared to be seeking shelter from the storm.Although
a golden eagle was seen flying from one of the towers the
following morning,during the rain storm was the only other
time during a 6-day stay near the lines that these species
Were Seen on the towers.
There was a raven (Corvus corax)nest on one of the
towers in the study area which ~ined four fully feathered
young birds.Hhile it was raining AN of 64 dB(A)and 69 dB
for the 125 Hz frequency was measured at a point on the
ground midway between the tower with the nest and the ad-
jacent tower.
AN on the right-of-way after the rain measured between
52-56 dB(A).The sound of the two lines was like loud
rushing water.Birds began singing again when the rain
stopped."Bits and pieces"of bird songs could be heard
through the noise.In the only span checked,6 birds,2 jack
rabbits and fresh (less than one hour old)coyote tracks,
were seen all within 40 m from the center of the right-of-way.
One of the birds,a sage thrasher,was perched and singing
just beyond an outer conductor.The noise was so loud that
the bird could just barely be heard from less than 60 m
away.Tlwse observations of wildlife utiliza tion of the
right-of-way under high AN conditions shows that the AN was
not causing birds and some other species to completely avoid
the right-of-way.
We feel that the difference in numbers of birds detected
on the right-of-way of the two SOO-leV transmission lines as
compared to the control can largely be explained by the
negative bias of AN on the observer.The degree of this
bias is probably partly determined by the hearing acuity of
the observer.However,more intensive studies are needed
to obtain more definitive information with which to evaluate
!our'preliminary findings.The possibility that AN or the
electric or magnetic field or other factors were affecting
birds on and near the ~ight-of-way to some degree cannot be
ruled out.One possibility for obtaining more definitive
information on the bias due to AN would be for the observer
to wear ear plugs when conducting counts on both right-of-way
and control transects.One problem,however,is that re-
latively few birds are detected solely by visual means.By
completely eliminating hearing as a means of detecting birds
the number of birds sampled would be extremely low.The
effects of low sample sizes'would then add to the difficulty
of testing for differences between the right-of-way and con-
trol areas.To determine what levels of transmission AN
mask bird calls and songs of various birds at varying dis-
tances from an observer,tape recorded sounds could be used
in both laboratory and field situations.
Transmission Line Raptor Study
Preliminary work with raptors during the d-c transmission
line study led to the development of a project to obtain
information on the effects of other BPA tr.:msmission lines on
this group of birds (Lee 1976).Until recent years,the
effects,both beneficial and adverse,that transmission
lines have on raptorial birds have not received a great dealofstudy.
Part of the BPA raptor study involves obtaining in-
formation with which to determine how extensively trans-
mission line structures are utilized as raptor'nesting sites.
For purposes of this study raven nests are also being counted.
Information is being obtained in an attempt to answer such
~~))1 L.
I i -.1 J ·1 J j I
154 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 155
Table 7.Number of bird nests observed on BPA 500-kV a-c
.and ±400-kV d-c transmission line structures
during helicopter patrol flights in April and May
1977.
SOD kV a.c_.__±400 kV d.c.
Non-Non-
Forested*Forested+Forested**Forested-t+
Total Length of 2024 1552 103 323
Lines Patrolled
(km)
Number of Nests:
Hawks 5 41 6 4
Ravens 0 35 1
Golden Eagle 0 0 0 1
Unknown ,0 56 1
Total Nests 5 132 7 6
questions as:1)which bird species are nesting on tranS-
mission structures?2)where are nests located on various
type structures?3)what site characteristics determine
whether transmission line structures are utilized fbr nesting
sites?4)does the electrical and acoustical environment
within transmission towers have an effect on nesting birds?
5}how much annual raptor production occurs on BPA trans-
mission line structures?
Birds nesting on EHV towers are exposed to AN·and
electric and magnetic field levels which greatly exceed
those found at ground level.This provides an opportunity
to study the possible effects of these parameters on adult
birds and their young.
BPA is also installing a small number of artifical
raptor nest platforms to evaluate their effectiveness in
reducing maintenance problems caused by bird nests located
over conductors.The feasibility of providing more de-
sirable nest sites for large raptors is also being studied.
The nest platform being installed was designed by Morlan
Nelson and the Idaho Power Company (Nelson and Nelson 1976).
On April 1.1977 helicopter patrol observers began
collecting information on nesting raptors.'fable 7 shows
the preliminary data collected for EHV lines through May
1977.It appears that many of these nests are successfully
producing young birds although this information is still being
developed.A much larger number of nests are located on
230-kV and lower voltage BPA transmission lines and this
information is also still being compiled.
Many of the nests on 500-kV lines are located on delta
configuration towers.Figure 10 shows a delta tower and gives
electric field strength and AN levels in some of the locations
where birds are known to perch and nest.It should be pointed
out that electric field measurements were made with a meter
designed to measure in uniform field areas such as on the
ground beneath a transmission line.The electric field in
the tower is actually perturbed by the metal structure so
the measurements in Figure 9 are only approximations.AN
,levels were calculated by Mr.Vern Chartier of BPA based on
the work of Perry (1972)and on his own work with 765-kV
lines.
As shown in Figure 10 during rain AN within the 500-kV
tower strung with a single 6.35 em conductor for each phase
could reach 76 dB(A)or more.Most SOO-kV 1ipes in the BPA
system utilize either the double or triple conductor bundle.
,~
+
lb~
++
Lines in this category are located primarily in central
and western Oregon and Washington and in Idaho In coni-
ferous forest,vegetation types.
Lines in this category are located primarily in eastern
Oregon and Washington'in shrub/grass and grass vegetation
types.
This category consists primarily of Western juniper
(Juniperus occidentalis)vegetation type.
This category consists primarily of sagebrush (Artemisia
spp.)grass and cropland.
C~1 J J .l·l J 1 J I J J 1 j
156 JACK M.LEE,JR.,AND DENNIS B.GRIFFITH TRANSMISSION LINE AUDIBLE NOISE 157
The effect of transmission line AN on people is an en-
vironmental issue.Annoyance including possible inter-
ference with sleep is one of the'most serious conse-
quences of AN on people.When relating the human
situation to wildlife several distinctions should be
made.For wildlife,it is important to consider the
maximum AN which occurs on the right-of-way.Differences
in hearing abilities between man and wildlife should
also be considered.With wildlife the effects of AN
may not be entirely negative.It is possible that
AN from transmission lines is a source of locational
information for some species.
On one line that does have the single conduc tor design for
its entire length (Vantage-Raver)a total of 13 nests were
counted this spring.Apparently birds are not completely
avoiding such lines because of their high AN characteristics.
CONCLUSIONS
It shoUld be pointed out,however,that most of the
nests on the Vantage-Raver SOO-kV line are located cast of
UIC Cascade Mountains in a relatively dry climate.From
Harch through May the mean precipitation is 51 nun and it
is only 25 mm to 51 mm from June through August (Highsmith
and Bard 1973:49).In this area precipitation and,there-
(are,the highest AN levels would occur only infrequently
during the nesting season.The possible effects of AN of
76 dB(A)or more occurring for long periods of time on adult
and young birds nesting in towers has yet to be determined.
Woolf et al.(1976)reported that auditory stimulation of
Japanese Quail eggs affected the developing embryo.It was
found that 37 msec.bursts of sound of .0.1-8 kHz with a
sound pressure level of 80 dB applied for two hours accele-
rated the time of hatching of the eggs by as much as 10 per-
cent.
1.Transmission line audible noise (AN),produced by corona
primarily from EHV lines,is one of many factors which
contribute to the unique characteristics of a trans-
mission line right-of-way.Any field study of the
effects of transmisssion line AN on wildlife should ac-
knOWledge the possible synergistic actions of construc-
tion and maintenance activities,and effects due to
electric and magnetic fields.To properly evaluate the
potential impact of AN on wildlife requires a basic
understanding of the technical aspects of AN.
2.
Electric Audible Noise During
Field Rain dBtA)
Strength Conductor Configuration
kV/m lx6.35cm 2x4.07cm 3x3,31cm
5 0 Mean 70 62 54
,Max.73 55 57
2 5 Mean 70 62 54
,Max,73 66 57
40 0 Mean 72 65 56
.Max,76 68 60
~
~
CD
(1)
@
Location
&i.~t~;~~~tif(~I~~l)f~~
Measured electric field strength and calculated
audible noise for locations within a typical
B.P.A.500 kV a-c transmission line tower where
raptors and other birds are known to perch and
nest.
Lf'~.¥q
l
E
"ci
E
Lt'l,..;
M
Figure 10 -
~
158
1
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
-1 JC~j j --J j -J
TRANSMISSION LINE AUDIBLE NOISE
)
159
3.Relatively fe~'l studies have been conducted to determi.ne
the effects of transmission lines on wildlife.Of those
which have been dane,still fewer have addressed the
possible effects of AN or other electrical parameters.
In studies conducted on Bonneville Power Administration
transmission line rights-of-way both positive and
negative effects of the right-of-way environment have
been identified.The nature and magnitude of these
effects has varied among species and taxonomic groups.
Although we do not discount the possible effects of
AN or electric fields,we believe that ecotogical effects
observed to date can largely be explained by physical
changes in habitat due to construction and maintenance
activities.
4.The effects of AN on even the most sensitive wildlife
species may be difficult to detect in field studies due
to marked temporal and spatial variation in wildlife
populations.A possible exception is the reindeer,the
behavior of which is reportedly affected by transmission
line AN (Villmo 1972).The possibility of sampling bias
due to the effects of AN on observers,and the fact that
highest AN levels occur during foul weather,a time
when wildife behavior is not well understood and when
most wildlife observational techniques are severly in~
paired add to the difficul ties of identifying the.
effects of AN on wildlife.
5.Increased public awareness of environmental pollutants
such as transmission line AN has served to promote
transmission line designs that minimize the production
of AN.We would expect this trend to continue so that
AN from newer EHV and UHV lines will be less than that
produced by some of the first EHV lines constructed.
RECOMl1ENDATIONS
Although a growing number of studies are being conducted
to determine the effects of transmission lines on wildlife,
few such studies acknowledge the unique characteristics of
the transmission line environment which distinguish it from
other rights-of-way.We recommend that persons conducting
such studies familiarize themselves with the technical char-
acteristics of transmission lines.Most biologists have
little or no training which is applicable to the highly
specialized subject fields which are concerned with the
theory and operation of EHV and UHV (ultra-h1gh-voltage)
transmission lines.We have found it necessary and extremely
helpful to consult with a number of persons who have the
necessary training to assist in designing and implementing
studies which consider the electrical parameters of trans-
mission lines.At the minimum we believe that reports of
biological studies done on transmission line rights-of-way
should provide sufficient information to describe the total
right-of-way environment.'Included should be such information
as the number and voltage of lines present,the range of
operating voltage during the study,the design of the line(s)
including the size and number of subconductors,and the
minimum conductor to ground clearances.Measurements of AN
or at least subjective judgements of the levels encountered
during the study should also be included.Other useful
information would include the dates when the line was con-
structed and energized,the use made of access roads,and
the kil)d of vegetation management activities utilized in-
cluding information on the use of herbicides On the right-of-
way.
ACKNOWLEDGEMENTS
Several persons provided much appreciated assistance
and advice during development and review of this paper.We
especially want to thank Dr.Dan Bracken,Physicist,and
Messrs.Steve Sarkinen,Stan Capon,and Vern Chartier,
Electrical Engineers,all from BPA,for their help.We
are also grateful to Dr.Lee Rogers and Mr.John Hedlund of
Battelle Northwest Laboratories [or their review of the draft
and for use of preliminary data from their studies o[the
BPA 1100/1200-kV Prototype Line.
Funds for travel to Madrid for the senior author were
provided by the U.S.Environmental Protection Agency,
through the Office of Noise Abatement Control.We greatly
appreciate the support provided by that Agency.We especiallY
wish to thank Dr.John Fletcher for his efforts in arranging
the conference session on the effects of noise On wildlife
and for inviting our participation in this conference.
This paper reports on research funded primarily by the
Bonneville Power Administration.BPA also provided financial
Support and arrangements for travel.
JACK M.LEE,JR.,AND DENNIS B.GRIFFITH
~
160
C~~~~~1 1 1 1 1 i J ~I ~--J --]i
TRANSMISSION LINE AUDIBLE NOISE
i
161
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I
I
OCEAN NOISE AND THE BEHAVIOR OF tIARINE ANU1ALS:
RELATIONSHIPS AND IMPLICATIONS
A~thur A.Myrbe~gJ Jr.
Rosenstiel School of Marine and Atmospheric ScienceUniversityofMiami
Miami,Florida
INTRODUCTION
There is general agreement among biologists that the
acoustical sense of aquatic animals probably constitutes
their most important distance receptor-system.This is par-
ticularly true among members of two vertebrate lines,the
fish~s and the marine mammals,whose acoustical activities
have been invc'stigated at an evcr-increasing rate of sophis-
tication during recent years.A major conclusion drn~l from
these varied studies -inclusive of those using psycho-
physical,physiological and ethological methodologies -is
that the acoustical system can,and does,provide its owner
appropriate information,readily and rapidly,on ?variety of
functions relative to food,competitors,potential mates and
predators.
Con.comitant with the increasing sophistication of pro-
blem-queries,experimental designs and available instrumenta-
tion,there is a growing awareness that ambient noise,itself,
can no longer be ignored in underwater bioacoustics.Not
only is it probable that such noise actually affects,at
least temporarily,the hearing abilities of the animals con-
cerned,it may also act to inhibit sound production as well.
Such a reduction in acoustic transmission and/or its reception
can,of course,adversely affect the reproductive potential
or even the survival of any given species or population that
is dependent on such a sensory process.Additionally,
evidence is beginning to show up which indicates that exces-
sive noise can also have other more direct.deleterious con-
sequences on marine biological systems (see below).This
problem-area will become more widely recognize~as more is
"......_.,..'_'~~N_.......L.