EPA 908/1-79-003
\
vironmental
Noise
Levels
IN THE
Grand Teton
National
Park
U.S. ENVIRONMENTAL PROTECTION AGENCY REGION VIII
AIR AND HAZARDOUS MATERIALS DIVISION
DENVER COLORADO 80295
HOVEMBER 1979
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EPA 908/1-79-003
November 1979
ENVIRONMENTAL NOISE LEVELS
IN THE
GRAND TETON NATIONAL PARK
BY
William C. Bryan
Larry L. Svoboda
Robert A. Simmons
John M. Brink
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
AIR AND HAZARDOUS MATERIALS DIVISION
DENVER, COLORADO 80295
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DISCLAIMER
This report has been reviewed by the Air and Hazardous Materials
Division, Region VIII, U.S. Environmental Protection Agency, and approved
for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
DISTRIBUTION STATEMENT
This document is available to the public through the National
Technical Information Service, Springfield, Virginia 22161
ii
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PREFACE
A draft environmental impact statement*, related to a proposal to
expand the Jackson Hole Airport near Jackson, Wyoming, was received from
the Federal Aviation Administration for review by Region VIII, U.S.
Environmental Protection Agency. Jackson Hole Airport is located within
the southern boundaries of the Grand Teton National Park and is operated
under a lease arrangement with the National Park Service.
It was apparent that one result of the proposed airport expansion
would be increased flight operations to include the flight of larger and
louder aircraft over the Grand Teton National Park. Also, it was
realized that the available documentation of existing noise levels in the
Park was not extensive enough to support valid comments on the noise
impact of the proposed expansion. Although little time remained before
comments were due, we considered it imperative that more data be
obtained. Representatives of the National Park Service concurred; and,
with the logistical assistance of the Park Service, personnel of the
Region VIII Office of the U.S. Environmental Protection Agency executed
the noise survey upon which this report is based during the period
January 10 to 19, 1978.
iDraft Environmental Impact Statement for the Jackson Hole Airport
Master Plan, October, 1977.
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ABSTRACT
Results of an environmental noise survey in the Grand Teton National
Park during the period January 10 to 19, 1978 are presented and
discussed. It is pointed out that man made or unnatural sounds are more
noticeable in that otherwise quiet environment than in most inhabited
environments. The survey procedures included statistical and graphical
recordings for extended periods (one or more days) and graphical
recordings for brief periods (minutes) at several locations. Also
discussed are questions related to the treatment of wind-induced noise
and internal noise in the measuring instruments when used in a quiet
environment.
IV
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CONTENTS
Disclaimer ii
Preface i i i
Abstract iv
Fi gures v"i
Tab!es vl i
Abbrevi ati ons and Symbols vi i i
Acknowledgements ix
Introduction 1
Conclusions 1
Recommendations 2
Instrumentation 4
Calibration of Instruments 6
Monitoring Sites and Procedures 7
Weather 8
Measurements During Extended Periods 9
Brief Measurements 1°
Appendix: Wind-Induced and Instrumental Noise 55
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FIGURES
1. nap or trie rion i tur my o i i.ca
2a. Monitoring Site at Moose
2b. Site above Taggart Lake
2c. Elbow Ranch Barn
2d. Elbow Ranch Cabin No. 3
A ~ c- **..*. A \ **\ir\"\ r* -a 4- Cl K/MJI D an/~H Rav^n Mo^C 1 jy*pH hv ^ V^t'Pm B . . . . . i
43. oOUnd Levels at tlOOW Kancn uarti ncaaurcu uy ojriocui u ......
-i f* * j ( AK A In ^4- C IK /M.I Dan/*h Ravn Mo^CIIV^AH nv SX/^"f"PfTl R
4b. Sound Levels at tioow Kancn earn neabureu uy oybucm o
/i c* **..-* A l^tf^l^ r»4- Cl K/M.I Dan/*h Rav*n Mo^C 1 JV^pH h\/ ^ V^tPm R . * . ,
4c. Sound Levels at tioow Kancn tsarn ricaaurcu uy ojrai/cm o
»i c*-*,.«*J IrNtf^lr* ^4- CT kru.i Dan/*h Rayn MpACMV*pH hv ^ V^1"Pni R .....
4d. Sound Levels at tioow Kancn Darn ricaburcu uy jysucni o .....
H £**%..«*! ! At«x^l^ -^-l- C7 Kni.i Dan/*h RaKTi Mp^CMK*pH hv ^V^f'PfTl R .....
4e. Sound Levels at tioow Kancn Darn riKaburcu uy oyiocm u .....
9. Combination of Environmental, Wind-Induced, and
Instrument Noise
..14
15
15
16
17
18
19
20
21
, 22
, 23
24-
, 25
26
27
28
29
30
31
32
*» ^
33
o yi
34
o c
35
f\ f*
36
37
38
57
c r»
58
10. Combination of Environmental, Wind-Induced, and
Instrument Noise
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TABLES
1. Weather at Elbow Ranch 39
2. Weather at Moose 40
3. Results of Measurements for Extended Periods 42
4a. through 4j. Sound Levels at Moose Measured by System A 43
5. Data from System B 53
6. Results of Brief Measurements 54
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ABBREVIATIONS AND SYMBOLS
L/\= A-weighted sound level expressed in decibels (dB) and referred to
a reference pressure of 20 micronewtons per square meter (2xlO~5
N/m2).
Lx= the A-weighted sound level that is exceeded x% of the time.
Lmax= The maximum A-weighted sound level (Lmax=Lo).
Leq (T)= equivalent sound level for the period of time, T; i.e., the
constant A-weighted sound having the same energy content as the actual
varying level, expressed mathematically as follows:
)o.
'10
dt
where:
i and t2 define the time period in hours
P0= 2xlO-5 N/m2
p$ is the mean square A-weighted sound pressure
Ldn= day-night sound level, equal to the Leq (24 hrs) modified by
having 10 dB added to each sound level measured between 10:00 p.m. and
7:00 a.m., and expressed mathematically as follows:
vm
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ACKNOWLEDGEMENTS
With gratitude, we acknowledge the hospitality and logistical
assistance, including electric power and warmed shelter for instruments,
provided by the National Park Service and the Teton Science School.
We are grateful to the City of Denver, Department of Health and
Hospitals, Office of Environmental Health Services for the use of a
microphone extension cable and to H.E. McKenna of Boulder, Colorado for
confirming the accuracy of the Bruel & Kjaer Pistonphone that served as
one of our two sound level calibrators.
Dr. Kent Williams, Jim Orban, and Ron Estes of the Region IV Office
of the U.S. Environmental Protection Agency aided in the presentation of
data collected by System A as a demonstration of recently-developed
computer techniques for analysis of data recorded in digital form on
magnetic tape cassettes, a much appreciated service.
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INTRODUCTION
Noise, according to the USA Standard on "Acoustical Terminology,"2
is any undesired sound. It follows that what is noise in one setting may
be unlike what is noise in another setting. One can support the thesis
that noise in the Grand Teton National Park is any unnatural or
human-made sound because the Congress apparently intended the Park to be
a place where people can experience a part of nature that is relatively
undisturbed by humans.
The activity upon which this report is based has been referred to as
a survey of environmental noise levels in the Grand Teton National Park,
but the label is misleading. It was a rather brief survey of sound
levels at a few locations in the Park with minimal attempts to identify
sound sources and to characterize sounds as noise or otherwise. Although
no single aspect of the acoustic environment is completely described by
the results, what is revealed is a somewhat more detailed description
than we previously had of the A-weighted sound levels that were typical
in winter at a few points in the Park. Against this limited backdrop,
one can begin to consider the probable impact of hypothetical changes in
the environment such as, for example, the addition or removal of a given
number of aircraft of a certain type that are operating in some assumed
manner. Beyond that, we trust that this survey has been of value as a
learning experience - a springboard from which complementary and more
complete efforts may come about in the future.
Figure 1 is a map of the Grand Teton National Park which may be used
for reference to the various monitoring sites that will be mentioned on
the following pages. Photographs of some of the sites are shown in
Figures 2a through 2f.
CONCLUSIONS
It is concluded that:
1. In the Grand Teton National Park, situations sometimes exist in
which one may experience a combination of scenic beauty and
quietness that most Americans seldom, if ever, experience.
2. Frequently heard in the Park are man made noises, out of concert
with the environment in its natural state, that tend to oppose
ones enjoyment and admiration of the beauty and quiet. Although
the levels of these noise intrusions are generally below what is
usual in much of America, they distract and annoy people, partly
2. ANSI Standard SI.2-1960 (R1971), Page 10.
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because they are out of character with the Park's natural
amenities and partly because they are interspersed with
contrasting periods of much lower sound levels.
3. Of the frequent man made noises in the Park, probably the most
pervasive and annoying are those caused by aircraft.3
4. The total noise environment in the Park cannot be characterized
without a more comprehensive effort to include more locations
and varied seasons. In addition, more specialized instruments
are needed for this type of environment.
RECOMMENDATIONS
Besides providing data that we trust will be useful, this survey in
the Grand Teton National Park emphasized to the participants that a
better job can be done. Toward that end, we recommend consideration of
the following items:
1. Other sites should be surveyed, including the major acoustic
environments that were not reached this time. In particular,
some back country and some visitors' residential areas should be
included. The choice of sites should take into consideration
their accessibility at all seasons.
2. Attitudinal surveys should be conducted to assess the concerns
of residents, employees, and visitors regarding noise; and the
results should be considered in reference to the intent of the
Congress in establishing the Park.
3. Surveys should be conducted at other seasons to reflect the
seasonal variations of noise and of the concerns of the
population.
^Many graphical records of aircraft noise were made but are not
discussed further in this report because in most instances no observers
were present to confirm the source identifications.
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4. The sound level measurements in future surveys should provide
values of Leq (24) and Ldn for comparison with the U.S. EPA
"Levels Document."4 Also, it is essential that several
exceedance levels be provided, including at least LQ, LI,
LlO» L20> and L90-
5. Sound level instruments for this environment should be designed
for low internal noise and have a dynamic range capable of
measuring the noise of low-flying aircraft. The latter
objective would call for measurement of maxima at 80 dB or
higher. The instrumentation should be relatively insensitive to
electrical interference.
6. We recommend that instruments be provided and programmed to deal
with wind-induced noise. What seems to be called for is: (1) a
fast-response wind speed sensor that is silent and can be
mounted very close to the microphone to eliminate most errors
due to spatial and temporal variations in the wind; (2) a known
mathematical relationship between wind speed and wind-induced
noise for the given microphone; (3) a programmed calculator that
will calculate real-time wind-induced noise, subtracting its
effect and that of the instrumental noise from the microphone
output before registering the result; and (4) a simultaneous
recording of the level of wind-induced noise for use in judging
the degree of confidence in recorded sound levels.
7. We recommend that instruments be provided (preferably the same
as suggested in item 6) which can distinguish, by frequency
content or otherwise, between natural and unnatural sound and
can provide statistical analyses of either independently.
8. It is observed that any future surveys should include protection
from weather extremes for the instruments and should provide for
continuous recording of weather data to include at least wind
speed, wind direction, and temperature.
(These recommendations are made for the purpose of encouraging
discussion and development of better methods and instruments. They are
not intended to serve as invitations for proposals to the U.S.
Environmental Protection Agency.)
^Information on Levels of Environmental Noise Requisite to Protect
Public Health and Welfare with an Adequate Margin of Safety.Report No.
550/9-74-004, U.S. Environmental Protection Agency, Washington, D.C.
20460, 1974.
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INSTRUMENTATION
We monitored sound levels at five locations for extended periods of
time by means of three instrument systems, each including a digital sound
level analyzer and a graphic recording device. A fourth system,
consisting of a precision sound level meter with a portable graphic level
recorder, was used for short periods at ten locations. A portable
weather station was operated at one location.
In more detail, the instrument systems were as follows:
System A: System A was a custom noise monitoring system, most of
which was assembled for the U.S. Environmental Protection Agency by the
U.S. Army Civil Engineering Research Laboratory, and included the
following components:
1. Outdoor Microphone, B & K Model 4921;
2. Log Voltmeter/Converter, Hewlett-Packard Model HP 7562A;
3. Programmable Calculator, Wang Model 600-14 TP;
4. Scientific Tape Recorder, Nagra Model IV-SJ;
5. Power supply and custom circuitry;
6. Graphic Level Recorder, GenRad Model 1521-B, with an 80 dB
potentiometer;
7. Anemometer, Science Associates Model 420-1.
This system was programmed to sample A-weighted sound levels ten
times per second and to provide statistical analyses of the sounds
registered during each successive half hour. Sounds registered during
wind speeds exceeding 15 km/hr were not included in the analysis. The
electronic noise floor was about 32 dB, and the range extended to 100 dB.
A few analog tape recordings of the flat (unweighted) sound levels
were made by use of the microphone of System A and the Scientific Tape
Recorder.
System B: This included the following components:
1. Community Noise Analyzer, GenRad Model 1945;
2. Electret-condenser microphone, 1 inch, GenRad Model 1961-9601,
as part of the Weatherproof Microphone and Housing Assembly,
GenRad Model 1945-9730;
3. Preamplifier, GenRad Model 1560-P42;
4. Strip Chart Recorder, Hewlett-Packard Model 7155A.
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System B was programmed to measure A-weighted sound levels at
intervals ranging from 0.2 to 0.7 sec, usually for three successive
periods totalling about 24 hours. The three periods were chosen in such
a way that one eight-hour period would approximate the defined nine hours
of night time which is from 2200 to 0700 hours. The instrument has no
nine-hour capability. A statistical analysis of the levels registered
during each period was provided, making it possible to later calculate
the equivalent sound level, Lgq, for the entire three periods and an
approximation of the day-night sound level, L(jn.
The range extended from about 18 dB to 120 dB; however, the system
was sensitive to electromagnetic noise, resulting in brief impulses of
high amplitude which affected some values of LQ (the period's maximum
sound level) and Leq. Those values that were suspect have been omitted
from this report.
System C; The following components comprised this system:
1. Sound Level Analyzer, Metrosonics Model db602;
2. Electret-condenser microphone, GenRad Models 1961-9601 (one
inch) and 1962-9601 (1/2 inch) used at different times, with
wind screen;
3. X-Y Recorder, Hewlett-Packard Model 7015A.
System C was programmed to sample A-weighted sound levels eight
times per second, disregarding any measurements during wind speeds
exceeding 15 km/hr. For each half-hour period it registered four noise
descriptors that were later made a matter of record via direct control of
the X-Y Recorder. The electronic noise floor was about 31 to 33 dB with
the 1/2 inch microphone and about 24 to 25 dB with the one inch
microphone. The upper limit of dynamic range was 120 dB for-the one inch
microphone and 130 dB for the 1/2 inch microphone.
System D; This portable system had the following components:
1. Precision Sound Level Meter, GenRad Model 1933;
2. Electret-condenser Microphone, GenRad Models 1961-9601 (one
inch), with wind screen;
3. Graphic Level Recorder, B & K Model 2306.
Calibrators: Two sound level calibrators were used frequently
during the survey for accuracy checks of Systems B, C, and D. They were
a B & K Pistonphone Model 4220 and a GenRad Sound Level Calibrator Model
1562A.
Weather Station: A portable mechanical weather station, Meteorology
Research, Inc., Model 1072, was located approximately 15 meters from and
behind Quarters Number 170 in the residential area at Moose. The device
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provided a continuous strip chart record of wind direction, temperature,
and air movement, from which average wind speed could be calculated.
CALIBRATION OF INSTRUMENTS
Within six months before the survey, all instruments were calibrated
with National Bureau of Standards traceability except as follows:
(1) The calibration of System A was less recent, but it exhibited
good agreement with the other Systems, and it was equipped with
an electrostatic actuator for frequent checks of precision.
When later calibrated by the manufacturer on January 11, 1979,
the man who did the calibration said that he found no reason to
suspect errors greater than a fraction of a decibel.
(2) The Hewlett-Packard Strip Chart Recorder and X-Y plotter were
not calibrated, but both are linear instruments with capability
of adjustment at any two points for agreement with the input
instrument, a practice that was routine during the survey.
It was our general practice during the survey to use one or both of
the two calibrators, or the electrostatic actuator for System A, to
adjust the measurement system for accuracy at the beginning of a
monitoring period and to recheck the system at the first opportunity upon
or after termination of the period. Precision in reading Systems B and C
was no better than i 1 dB because their digital displays had that
limitation. The display for System A gave readings to several decimal
places. Drift in accuracy with reference to the calibrators or
electrostatic actuator from beginning to termination of a monitoring
period was not observed to exceed i 0.3 dB for System A, i 2 dB for
System B, and ± 2 dB for System C. Comparisons between readings of the
two calibrators were within 1 dB. Slight differences may be attributable
to operational difficulties in cold weather.
In accordance with American National Standard, ANSI SI.4-1971, and
manufacturers' instructions, corrections were applied to calibrator
readings as follows:
B&K 4220 GenRad 1562-A
Sea level value (dB) 123.9 at 250 Hz 114 at 1000 Hz
A-weighting coorection (dB) -8.6 0
Elevation correction for
1980 to 2130 m. (dB) -2.1 -1.6
Corrected value (dB) 113.2 112.4
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MONITORING SITES AND PROCEDURE
(See Figs. 1 to 2f)
Moose: At House Number 170 in the residential area of the Park
Headquarters at Moose, Wyoming, System A was used to monitor sound levels
for 178 hours, 87 percent of the elapsed time between 2200 hours on
January 10, and 0900 hours on January 19.
At the same location, System B was used to monitor for 46 hours
between 1500 hours on January 13 and 1400 hours on January 15. Some, but
not all, of the System B data at Moose were affected by electromagnetic
interference, probably originating in the house heating system.
Excepting pre-amplifiers, the electronics equipment was protected
indoors from temperature extremes, while the microphones and
preamplifiers were mounted on a clothesline pole approximately 1.5 meters
above snow surface and eight meters from the house toward the rear. The
portable weather station was about 15 meters behind the same house.
Sound levels at the Moose site were generally higher than at the
other sites monitored, due partly to the site's position in relation to
the Airport and partly to other cultural activity in the vicinity.
Elbow Ranch Barn: System C was installed at Elbow Ranch with the
electronics package inside the unheated log barn and the microphone about
eight meters to the east and up the north-slope hillside from the barn.
The microphone was supported on a tripod that was cantilevered from a
tree trunk at a height of about 1.8 meters above the snow.
A ski trail passed within about six meters of the microphone; and
there was evidence that at least one snowmobile used the trail
occasionally, contributing to the values of LQ and Leq if not to the
other descriptors.
Monitoring at the Elbow Ranch Barn continued for a total of 156.5
hours, 91 percent of elapsed time between 1330 hours on January 11 and
1800 hours on January 18.
Elbow Ranch Cabin Number 3; Cabin Number 3 at Elbow Ranch was in a
quieter location than the barn because it was not near the ski trail.
System B monitored there for 24 hours from 1500 hours on January 17 to
1500 hours on January 18. With the Community Noise Analyzer kept warm
indoors, the microphone and preamplifier were about 1.8 meters above the
snow surface among the trees at a distance of about ten meters from the
cabin. The strip chart recorder was not used at this site for fear that
it might provide a path for power line noise interference with the
Community Noise Analyzer.
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Moran Village; System B was installed at Mobile Home Number 480 in
Moran Village where it monitored sound levels for 39 hours between 1800
hours on January 11 and 1100 hours on January 13. The microphone and
preamplifier were about 1.5 meters above snow level in a thin grove of
trees about 15 meters behind the mobile home. The other instrumentation
remained warm inside the home. Sound levels at Moran were among the
lowest ones measured during this study.
Beaver Creek: Sound levels near Mobile Home Number 447 at Beaver
Creek were monitored by use of System B for 24 hours between 1030 hours
on January 16 and 1030 hours on January 17. The microphone and
preamplifier were at the edge of a grove of trees, about 1.5 meters above
the snow and about nine meters behind the mobile home, with the remaining
instrumentation kept warm inside the home.
WEATHER
Table 1 summarizes some weather observations that were recorded by
personnel of the Teton Science School at Elbow Ranch. The data of Table
2 were extracted from a strip chart recording made at the Moose
monitoring site by our portable weather station. Information on
wind-induced noise found in Table 2 is discussed in the Appendix.
8
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MEASUREMENTS DURING EXTENDED PERIODS
Table 3 presents some equivalent sound levels (Leq) and day-night
sound levels (L,jn) based on this survey. The daily periods used for
calculation of these values extend approximately from noon to noon. The
noon-to-noon timing was chosen to facilitate comparison between
instrument systems because of operational requirements that Systems B and
C be interrupted for data retrieval and reprogramming near midday instead
of midnight. These values of daily Leq differ from those shown in
Tables 4a through 4j and Figures 3a through 3j because the latter
represent periods from midnight to midnight.
Table 3 shows the number of hours of monitoring that served as the
basis for each value of Leq. Consistent with the definition of Ldn,
day hours are defined here as all hours from 0700 to 2200 and night hours
are from 2200 to 0700. See comments on "System B" regarding an exception
to this treatment. In instances where monitoring produced data for less
than a full 24-hour day, any calculation of Ldn includes the assumption
that the day time Leq and the night time Leq would remain valid had
24 hours of data been available.
Tables 4a through 4j are computer transcriptions of data recorded
digitally on cassettes by System A. The deleted items are those that
have been questioned because of known or suspected interference or error
in procedure. Note that these daily le(, periods differ from those in
Table 3.
Table 5 shows more of the results from System B, including, as does
Table 4, some values of Lx» the level exceeded x percent of the time.
Data in graphical form, obtained over extended periods, are
presented in Figures 3a through 5e. Figures 3a through 3j are
computer-produced representations of System A data that had been recorded
in the field on digital cassettes. Figures 4a through 4e represent
System C data as transcribed in the field by the X-Y Recorder from the
memory of the Sound Level Analyzer. Figures 5a through 5e are copies of
sample graphic level and strip chart recordings from Systems A and B as
produced in the field.
To assist in the interpretation of the graphs of Lx and Leq, we
include Figure 6, a similar representation of environmental noise
recorded at a location 23.5m. from a rather busy four-lane street in a
medium-size city of Colorado. It is clear that, whereas the city street
noise produces considerable spread between all the Lx values, the Teton
National Park data show little spread between values of Lx except in
the vicinity of LQ and LI. This is evidence that the louder sounds
in the Park are relatively infrequent and, therefore, more intrusive than
would be true in the city.
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BRIEF MEASUREMENTS
We made brief A-weighted strip chart recordings at ten locations by
use of System D, using a dynamic range of 20 to 70 dB. At each location,
the microphone height was about 1.5m above snow surface. The site
locations are shown on Figure 1.
These samples are useful examples of presumably typical conditions,
but no claim is made that they represent the usual or average
conditions. Obviously, the results are not adequate for estimation of
such descriptors as Leq (24) or I_dn.
Table 6 summarizes the data, and a sample graphic level recording is
shown in Figure 7. The statistical analyses included in Table 6, other
than values of LQ, are calculated from strip-chart values taken at 5
sec intervals. Other observations peculiar to the respective sites are
given in the following paragraphs:
Site 1, Jackson Hole Country Club: The major noise sources
identified while recording at Site 1 were as follows:
Source Maximum Level (dB) Duration
High altitude jet aircraft 40 2 min
Construction (hammering) 42 discontinuous
Truck 51 30 sec
Single engine aircraft on approach 72 1 min
Automobile 39 15 sec
High altitude aircraft 47 50 sec
Also at Site 1, but not during the sampling, a Convair 580 aircraft
on take-off to the south was measured at 82 dB, after which it turned
east and then north and was audible for four minutes. The level during
take-off exceeded the ambient by 57 dB.
Site 2, Circle E. Road. At Site 2, the major noise source was
highway traffic, peaking at 28 dB and lasting for 10 to 15 seconds.
Site 3, Murie Ranch. During the sample at Site 3, a distant
single-engine aircraft peaked at 56 dB (35 dB above ambient) and was
audible for 30 seconds. Birds, audible for 50 seconds, peaked at 27 dB.
Site 4, Moose. During the three sampling periods at Moose, the
following sources were observed:
10
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SITE
SOURCE
MAXIMUM (dB)
DURATION
4a Automobile
4a Snow plow
4a Truck
4b School bus at 400m
4b Dog barking
4b Raven at 90m
4c Aircraft at high altitude
4c C-580 taxiing at airport
4c C-580 take-off to south
4c Twin engine aircraft 1000
feet above approaching
for south-bound landing
4c Twin engine aircraft,
reverse thrust on runway
27
28
29
29
32
38
59
36
40
62
51
10 sec
30 sec
30 sec
10 sec
discontinuous
20 sec
2 min
1 min
1.5 min
2 min
1 min
Site 5, Menors Ferry. During the three samples at Site 5, the
following noise sources were observed:
SITE SOURCE
5a River
5a Birds
5b Single engine aircraft
5c Snowplow
5c Truck on highway
MAXIMUM (dB)
52
62
68
41
56
DURATION
5 min
discontinuous
2 min
20 sec
2 min
Note that the aircraft heard at Site 5b was 33 dB above ambient.
Another single engine aircraft, not during the sampling period, peaked at
55 dB and was audible for nine minutes. Also, a high altitude jet,
measured up to 45 dB, was audible for more than one minute.
Site 6, Chapel Road. At Site 6 the sample included noise from a
high altitude jet that peaked at 55 dB, heard for five minutes, and from
a single engine aircraft peaking at 53 dB, audible for 70 seconds.
11
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Site 7, Taggert Lake.
following:
SOURCE
Noise sources identified at Site 7 were the
Observer noise
C-580 aircraft on south-bound approach
C-580 aircraft, reverse thrust on runway
C-580 aircraft taxiing at airport
Distant single engine aircraft
C-580 aircraft on south-bound approach
C-580 aircraft, reverse thrust on runway
C-580 aircraft, south-bound take-off
MAXIMUM (dB)
28
45
37
28
34
46
44
37
mm
min
DURATION
impulsive
3
1
1.5 min
3 min
4 min
2 min
1 min
In this back country site the aircraft sounds were from eight to 24
dB above ambient, even with distant source locations.
Site 8, Baseline Flats. At Site 8, the sounds of breathing and
clothing friction due to arm movements were prominent at 24 dB; and the
ticking of a loud pocket watch at 20 dB was noticeable. For half the
time, sound levels were below the instrumental noise floor.
Site 9, Antelope Flats. The peak noise level at Site 9, lasting
about 20 seconds, was due to a snow plow and measured 35 dB. A more
distant snow plow droned continuously at about 22 dB.
Site 10, Cunningham Cabin. Principal contributors to noise at Site
10 were the following:
SOURCE
Convair 580 estimated 11 km away
Aircraft, single engine
Automobiles on highway
MAXIMUM (dB)
39
36
34 to 38
DURATION
2 min
1 min 40 sec
20 sec. each
12
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mZi^ -.iJ9f
* £.M 5 ^'
.* # ' ,-v .
Fig. 1. Map of the Monitoring Sites
13
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Fig. 2a. Monitoring Site at Moose
Fig. 2b. Site above Taggart Lake
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Fig. 2c. Elbow Ranch Barn
Fig. 2d. Elbow Ranch Cabin No. 3
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Fig. 2e. Beaver Creek Site
*,
'ft
^»
Fig. 2f. Mo ran Village Site
ie
-------
100
JflNUflRT 10, 1978
90
eq
- 34. 31
o 80
OJ
ID
OQ
70
-------
JflNUnRY 11, 1978
100
90
o 80
C\J
CO
l_
CO
70
co
£60
CO
CO
o
~O
ID
C5)
r<
0)
3:
i
CE
50
30
20
_l - 48. 10
eq
LOO
L01
L10
L90
Time of Day
00 03 06 09 12 15 18 21 24
Fig. 3b. Sound Levels at Moose Measured by System A
18
-------
JHNUflRT 12, 1978
100
90 -Leq
o 80
C\j
OQ
70
_j
0)
CO
r-H
O
T)
(U
O)
50
40
30
20
- 41.52
LOO
L01
L10
L90
Time of Day
00 03 06 09 12 15 18 21 24
Fig. 3c. Sound Levels at Moose Measured by System A
IS
-------
JflNUflRT 13, 1978
100
90
o 80
OJ
QQ
70
0)
0)
CO
50
TJ
(D
O)
CL
30
20
eq
- 40.75
T i me of D3y
00 03 06 09 12 15 18 21 24
Fig. 3d. Sound Levels at Moose Measured by System A
20
-------
JRNURRT 14, 1978
100
90
o 80
cu
OQ
70
jso
CO
r-*
O
50
CO
cr
30
eq
- 36. 94
LOO
Time of Day
20
00 03 06 09 12 15 18 21
Fig. 3e. Sound Levels at Moose Measured by System A
21
-------
JflNURRT 15, 1978
100
90 -
C\l
OQ
80
ID
to
CO
r-H
O
60
50
CD
I
a:
30
20
eq
- 38c55
\/\7
Time of D3y
00 03 06 09 12 15 18 21 24
Fig. 3f. Sound Levels at Moose Measured by System A
22
-------
JfiNURRY 16, 1978
100
90
o 80
f\J
CD
70
H)
CO
»<
I 50
T)
CD
I
or
40
30
20
eq
- 49.96
LOO
L01
L10
L90
Time of Day
00 03 06 09 12 15 18 21 24
Fig. 3g. Sound Levels at Moose Measured by System A
23
-------
JflNUflRT 17, 1978
100
90
o 80
Od
ID
CD
70
ID
£60
0)
rH
O
z:
TJ
_c
CD
iI
ID
I
CE
50
30
20
eq
- 45. 14
\
LOO
L01
Time of Day
00 03 06 09 12 15 18 21 24
Fig. 3h. Sound Levels at Moose Measured by System A
24
-------
JflNURRT 18, 1978
100
90
o 80
C\J
QQ
70
ID
£60
Q)
CO
50
ID
_c
ID
zz:
i
CE
30
_!_. = 36.93
eq
LOO
Time of Day
20
00 03 06 09 12 15 18 21
Fig. 3i. Sound Levels at Moose Measured by System A
25
-------
JRNUflRT 19, 1978
100
90 -Leq
o 80
CM
CD
70
£60
CO
50
Q)
-C
O)
rH
Q)
I
CL
40
30
20
Fig. 3j.
- 45.66
Time of Day
i i i i
00 03 06 09 12 15 18 21 24
Sound Levels at Moose Measured by System A
26
-------
CO
-1
-------
-------
-------
-------
'
-------
GENERAL RADIO COMPANY. WEST CONCORD. MASS. CHART I52I-84Z8
'
Fig. 5a. Sample Graphic Level Recording at Moose
-------
IT
GENERAL RADIO COMPANY. WEST CONCORD. MASS. CHART IS;
<:
Fig. 5b. Sample Graphic Level Recording at Moose
-------
PBINtID IN U S ».
GENEB
V:
Fig. 5c. Sample Graphic Level Recording at Moose
-------
8/.ZO-08Z6 QWVXDVd-11
f r <
,
-.1
Fig. 5d. Sample Strip Chart Recording at Moran Village
-------
GENERAL RADIO COMPANY. Wt..f CONCORD. MASS.
.1,
Fig. 5e. Graphic Level Recording on a Windy Day
-------
23.5m from a busy four-lane street, Boulder, Colorado, September, 1975
HOUR 07 THE DAY
iii iii
00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Fig. 6. City Noise Included for Comparison
u
i
-------
BrOel & Kjaer
(.
<
-ll-l lit i . I I
QPQ102
Fig. 7. Sample Graphic Level Recording above Taggert Lake
-------
Table 1. Weather at Elbow Ranch
DATE
(1978)
0109
0110
0111
0112
0113
0114
0115
0116
0117
0118
MAXIMUM
(OF)
36
34
32
35
37
34
32
34
40
TEMP.
(°C)
2
1
0
2
3
1
0
1
4
MINIMUM
(OF)
10
12
19
21
14
12
20
19
18
TEMP.
(°C)
-12
-11
-7
-6
-10
-11
-7
-7
-8
BAROMETER
(cm of Hg)
76.3
75.8
75.8
76.1
76.8
76.4
75.3
75.6
75.5
76.2
NEW SNOW SKY
DEPTH (cm)
0 Pt. Cldy
0 Cloudy
3 Cloudy
4 Cloudy
Pt. Cldy
3.8 Cloudy
Cloudy
8.0 Cloudy
5.8 Cloudy
2.0 Cloudy
* Based on records of the Teton Science School,
Box 68, Kelly, Wyoming 83011
39
-------
TABLE 2. Weather Moose
DATE & TIME
FROM
0113.2005
0114.000
.0330
.0530
.0800
.1150
.1550
.2100
0115.0210
.0615
.0815
.1000
.1110
.1315
.1455
.1620
.1830
.2130
0116.0350
.0730
.0955
.1140
.1320
.1455
.1650
.1845
.2020
.2115
.2305
0117.0045
.0220
.0355
.0600
.0800
.1215
.1640
0118.0100
.0310
.0610
.1000
(1978)
TO
0113.2400
0114.0315
.0530
.0800
.1150
.1550
.2100
0115.0210
.0615
.0815
.1000
.1110
.1315
.1455
.1620
.1830
.2130
0116.0350
.0730
.0955
.1140
.1320
.1455
.1650
.1845
.2020
.2115
.2305
0116.0045
.0220
.0355
.0600
.0800
.1215
.1640
0118.0100
.0310
.0610
.1000
.1310
TEMP.(OC)
-9
-9
-10
-10
-10 to 3
-3 to 1
-4 to -3
-4
-5
-5
-4
-4
-4 to -3
-3
-3
-4
-4
-4
-4
-4
-3
-2
-2
-2
-2
-3
-4
-4
-4
-4
-4
-5
-4
-5 to 4
-2
-3 to -2
-5 to -4
-4
-5 to -4
-5 to 2
WIND
FROM
N
N
NNE
NNE
NNU
NE
variable
N
variable
variable
variable
N
NE
NE
N
N
NNE
variable
variable
SSW
SSW
SSW
SSW
SSW
SSW
SSW
SSW
SSW
s
s
s
s
s
ENE
variable
variable
variable
N
N
variable
AVG. WIND
SPEED (km/h)
4
5
8
6
4
4
3
3
4
8
9
14
8
10
11
7
5
3
4
7
9
10
10
8
8
10
18
9
10
10
10
8
8
4
4
2
0
1
4
5
Lw(dB)**
32
32
32
32
32
32
32
32
32
32
33
38
32
33
35
32
32
32
0*7
32
33
33
34
33
33
34
44
33
33
34
34
32
32
32
32
32
32
32
32
3i
*Based on portable weather station records
** Assumed wind-induced microphone noise for System A plus internal
electronic noise at the stated average wind speed. Gusts not accounted for.
-------
TABLE 2. (Continued)
FROM & TIME (1978)
FROM TO TEMP. (°C) WIND AVG. WIND
FROM SPEED (km/h) Lw(dB)2
.1310 .1530 0 to 2 S 7 32
.1530 .1730 -5 to 1 S 4 32
.1730 .2210 -11 to -5 VARIABLE 2 32
.2210 0119.0210 -18 to -11 VARIABLE 2 32
0119.0210 .0325 -18 to -17 N 7 32
.0325 .0505 -17 to -16 N 10 33
.0505 .0645 -16 NNE 10 33
.0645 .0810 -17 N 11 35
.0810 .0945 -17 N 10 34
41
-------
TABLE 3. Results of Measurements for Extended Periods
DATE & TIME (1978)
START STOP
FROM TO
SITE
SYSTEM A
0110.
0111.
2200
1200
0112.1600
0113.
0114.
0115.
0116.
0117.
0118.
1200
1200
1200
1630
1200
1200
0111
0112
0113
0114
0115
0116
0117
0118
0119
.1200
.0030
.1200
.1200
.1200
.1030
.1200
.1200
.0900
Moose
Moose
Moose
Moose
Moose
Moose
Moose
Moose
Moose
HRS.
5
9
11
13
13
13.5
10
15
12
DAY
6Q HK5. ^-£Q
44
52
41
42
39
51
48
39
39
9
2.5
9
9
9
9
9
9
9
SYSTEM B
0111.
0112.
0113.
0114.
0116.
0117.
1800
1100
1500
1600
1030
1500
0112
0113
0114
0115
0117
0118
.0900
.1100
.1500
.1400
.1030
.1500
Moran
Moran
Moose
Moose
Beaver
Creek
Elbow
7
16
16
14
16
16
29
30
40
32
8
8
8
8
8
8
35
41
38
33
33
34
37
36
46
24
22
28
21
NIGHT
HRS. Leq
14
11.5
20
22
22
22.5
19
24
21
176
15
24
24
22
24
24
133
40
51
40
40
38
49
46
38
43
44.8
27
29
39
30
COMBINED
Ldn
--
45
42
41
50
48
43
51
32
31
40
32
SYSTEM C
0111.
0112.
0113.
0114.
0115.
0116.
1330
1800
1200
1200
1200
1200
0117.1530
0118.1200
0112
0113
0114
0115
0116
0117
0118
0118
.1200
.1200
.1200
.1200
.1200
.0800
.1530
.1800
Elbow
Barn
Elbow
Barn
Elbow
Barn
Elbow
Barn
Elbow
Barn
Elbow
Barn
Elbow
Barn
Elbow
Barn
13.5
9
15
12.5
15
11
11.5
6
37
40
46
43
38
36
46
37
9
9
9
9
9
9
9
0
34
37
36
27
34
36
35
-
22.5
18
24
21.5
24
20
20.5
6
36
39
44
41
37
36
44
41
44
46
42
41
43
46
-
*L0, Lgn, and L^n affected by electromagnetic noise; therefore, not reported.
42
-------
Table 4a. Sound Levels at Moose Measured by System A
JANUARY 10, i97«
DBS TIME LEQ L99 L90 L50 LlO L01 L.I I 00
1 22:00 34.322 0. 33. 34. 35. 41. 46. 52.
2 22:30 33.729 0. 33. 33. 34. 40. 46. 51.
3 23:00 34.629 0. 33. 33. 34. 44. 49. 56.
4 23:30 34.519 0. 33. 34. 35. 41. 45. 49.
SUMMARY: 4 OBSERVATIONS AND LEQ = 34.31
43
-------
Table 4b. Sound Levels at Moose Measured by System A
JANUARY 11, 1978
DBS TIME LEQ L99 L90 L50 L10 L01 L.I LOO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
,um
00:
00:
01:
01:
02-
02:
03:
03:
04:
04:
05:
05:
06;
06:
07:
07:
08:
08:
09:
09:
10-
10:
11:
11:
12:
12:
13:
13:
14:
14:
15:
15:
16:
16:
17-
17:
19:
19:
20:
20:
21:
21:
22:
22:
23:
23:
lARy
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
: 46
33.
33.
33.
33.
33.
33.
35.
36.
32.
33.
32.
33.
40.
32.
33.
32.
33.
44.
37.
38.
32.
41.
52.
35.
41.
54.
55.
43.
4b.
46.
44.
43.
62.
42.
44.
38.
34.
33.
36.
34.
35.
45.
38.
35.
42.
43.
462
034
339
159
009
358
386
631
732
251
668
761
829
580
582
416
555
793
461
725
241
291
789
240
3/7
271
535
041
115
600
181
915
307
242
842
033
171
843
065
925
954
034
060
7b8
061
569
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
o.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
OBSERVATIONS
33.
33.
33.
33.
33.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
33.
32.
32.
35.
39.
36.
37.
37.
35.
34.
35.
34.
34.
33.
32.
32.
32.
32.
32.
33.
32.
33.
32.
33.
AND
33.
33.
33.
33.
33.
33.
33.
34.
33.
33.
32.
33.
36.
33.
33.
32.
33.
34.
33.
32.
32.
34.
35.
33.
33.
41.
45.
39.
45.
43.
41.
38.
45.
39.
40.
35.
33.
33.
33.
33.
33.
35.
33.
33.
33.
35.
LEQ
L.
34.
33.
33.
33.
33.
34.
38.
40.
33.
35.
34.
35.
44.
33.
33.
33.
35.
48.
39.
38.
33.
44.
46.
38.
38.
54.
54.
46.
51.
50.
48.
47.
62.
46.
48.
41.
35.
35.
37.
36.
37.
47.
39.
37.
41.
46.
= 48
= 49
37.
34.
38.
36.
34.
36.
42.
44.
35.
36.
36.
40.
51.
33.
34.
35.
37.
57.
49.
51.
35.
53.
65.
44.
55.
67.
70.
53.
57.
57.
53.
55.
76.
51.
55.
48.
40.
41.
46.
44.
46.
57.
50.
45.
53.
55.
.10
.21
41.
34.
41.
40.
34.
38.
43.
48.
41.
37.
37.
46.
54.
33.
38.
38.
40.
58.
51.
54.
39.
58.
77.
48.
61.
74.
74.
58.
63.
61.
58.
60.
79.
54.
59.
51.
46.
45.
52.
49.
51.
64..
55.
52.
64.
64.
52.
34.
43.
41.
34.
39.
44.
48.
49.
38.
38.
47.
55.
35.
66.
48.
42.
60.
53.
57.
48.
60.
80.
50.
65.
76.
76.
60.
67.
66.
64.
66.
81.
57.
63.
56.
57.
52.
57.
52.
60.
69.
57.
59.
67.
68.
dn
44
-------
Table 4c. Sound Levels at Moose Measured by System A
JANUARY
12, 1978
DBS TIME LEO L99 L90 L50 L10 L01 L.I
LOO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
00
16
16
17
17
18
18
19
19
20
20
21
21
22
22
23
23
:00
:00
:30
:00
:30
:00
:30
:00
:30
:oo
:30
:00
:30
:00
:30
:oO
:30
42.
45.
49.
43.
39.
38.
39.
36.
37.
36.
33.
34.
33.
39.
35.
34.
36.
987
710
761
412
624
717
708
813
121
491
432
582
502
618
404
092
838
0.
0.
0.
0.
0.
o.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
33.
33.
40.
34.
33.
34.
33.
33.
32.
32.
32.
32.
32.
33.
32.
32.
32.
35.
36.
47.
38.
35.
35.
35.
34.
33.
33.
32.
33.
33.
34.
33.
33.
33.
46.
43.
54.
47.
43.
40.
42.
39.
39.
39.
34.
36.
35.
42.
37.
35.
38.
55.
59.
57.
54.
51.
49.
51.
47.
48.
46.
40.
43.
40.
50.
45.
41.
47.
60.
67.
62.
57.
54.
55.
56.
51.
53.
50.
45.
48.
43.
5b.
49.
47.
55.
64.
72.
66.
68.
58.
59.
60.
56.
60.
63.
50.
50.
48.
61.
55.
52.
63.
SUMMARY: 17 OBSERVATIONS AND LtQ = 41.52
45
-------
Table 4d. Sound Levels at Moose Measured by System A
JANUARY 13, 1978
UBS TIME LEQ L99 L90 L50 LlO L01 L.I LOO
1
2
3
4
5
6
7
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
on
10
-> 1
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
00:00
00:30
01:00
01:30
02:00
02:30
03:00
03:30
04:00
04:30
05:oo
05:30
06:00
06:30
07:oo
07:30
08:00
08:
09:
09:
10:
10:
11:
11:
12:
12:
13:
13:
14-
i 4 .
15:
16:
16:
17:
17-
18:
18:
19:
19:
20:
20S
21:
21:
22:
22:
23:
23-
SUMMARY
30
00
30
00
30
00
30
00
30
00
30
Aft
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
40.016
46.294
40.828
35.973
34.064
34.408
37.124
38.637
35.990
34.345
32.743
33.917
37.512
36.634
33.151
33.254
33.511
34.328
33.783
42.703
32.
892
35.604
41.
33.
39.
49.
36.
47.
41
t A
41 *
48.
47.
34.
38.
34.
35.
32.
33.
39.
42.
43.
34.
33.
34.
34.
33.
33.
635
b7Q
663
866
982
113
A A n
000
n If
763
118
380
077
078
959
823
015
761
447
783
221
713
430
172
065
204
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
o.
0.
f\
/\
o.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
: -$V OBSERVATIONS
32.
35.
32.
32.
32.
32.
33.
32.
32.
32.
32.
33.
33.
33.
33.
33,
33.
33.
32.
32.
32.
31.
31.
31.
31.
32.
32.
33.
33.
33.
32.
32.
32.
32.
32.
33.
33.
33.
33.
33.
33.
34.
33.
33.
33.
AND
34.
43.
34.
33.
33.
33,
33.
34.
33.
33.
33.
33.
34.
34.
33.
33.
33.
33.
33.
33.
32.
32.
33.
32.
32.
32.
33.
35.
ifi
35.
34.
33.
33.
33.
33.
33.
33.
33.
34.
34.
34.
34.
34.
33.
33.
33.
LEQ
Ldn
44. 50.
50. 56.
45. 51.
38. 46.
35. 42.
36. 43.
39. 47.
41. 49.
37. 46.
35. 43.
33. 36.
35. 41.
39. 48.
39. 46.
34. 35.
34. 37.
34
36
35
43
35
33
39
35
37
39
39
44
c f\
43
42
36
39
34
40
33
33
36
36
39
35
34
35
35,
33,
34,
c
. 37.
. 40.
. 38.
. 55.
. 37.
. 49.
. 56.
. 42.
. 51.
. 62.
. 47.
. 60.
e- t
. 63.
. 61.
. 42.
. 49.
. 39.
. 43.
. 34.
. 34.
. 52.
. 55.
. 56.
. 37.
. 36.
. 39.
. 41.
. 34.
, 34.
4-0. 7$
A'* "^O
45.33
54.
59.
55.
51.
47.
48.
53.
54.
53.
49.
39.
44.
53.
50.
38.
40.
45.
43.
44.
63.
39.
52.
60.
50.
62.
73.
52.
69.
1 1
69.
69.
48.
55.
46.
46.
37.
35.
61.
65.
66.
39.
41.
42.
45.
36.
35.
57.
63.
56.
57.
52.
52.
56.
61.
59.
52.
43.
47.
56.
52.
40.
41.
50.
45.
57.
69.
43.
54.
63.
55.
67.
76.
62.
74.
76.
72.
51.
62.
65.
60.
40.
44.
64.
66.
68.
40.
47.
50.
47.
37.
37.
46
-------
Table 4e. Sound Levels at Moose Measured by System A
OBS
JANUARY 14, 1978
LE(j L99 L90 L50 LlO LOl L.I LOO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
1 A
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
00:oo
oo:30
oi:oO
01:30
02:00
02:30
03:00
03:30
04:00
04:30
05:00
05:30
06:00
06:30
07:00
07:30
08:oo
08:30
09:00
04 - ift
10:00
10:30
11:00
11:30
12:oO
12:30
13:00
13:30
14:00
16:30
I7:oo
17:30
I8:oo
lb:30
19:00
20:oo
20:30
21 :00
21 :30
22:00
22:30
23:00
23:30
4.
32.
33.
32.
33.
33.
33.
33.
34.
33.
33.
33.
33.
33.
33.
33.
33.
33.
34.
35.
"3 u
32.
42.
37.
38.
42.
40.
4^.
44.
42.
35.
33.
33.
35.
34.
33.
32.
32.
32.
32.
32.
33.
33.
33.
2
995
152
990
004
001
176
162
101
396
081
273
295
007
15]
229
134
459
182
447
6'
479
194
230
b9R
833
U09
342
520
613
495
670
073
b39
439
b«2
8bl
217
071
b44
9/4
237
OOb
057
SUMMAKY: -4-e-ubsLpVA
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
n
0.
0.
0.
0.
o.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
IIL'M
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
32.
3 <}
32.
32.
31.
31.
31.
32.
31.
32.
32.
32.
33.
33.
33.
33.
33.
32.
32.
32.
32.
33.
33.
33.
33.
5 AND
33.
33.
33.
33.
33.
33.
33.
34.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
a 7
32.
32.
32.
32.
32.
33.
32.
33.
33.
33.
33.
33.
33.
33.
33.
33.
32.
32.
33.
33.
33.
33.
33.
I.E9
Un
33
33
33
33
33
34
34
35
34
33
34
34
33
34
34
33
34
35
34
^S
33
34
38
40
34
40
38
43
43
35
34
33
34
33
34
34
33
32
33
33
34
33
33
=
*
*
9
*
36
JO
40
33.
3b.
33.
34.
33.
34.
35.
39.
35.
34.
35.
35.
33.
35.
35.
35.
37.
39.
45.
/\ \
38.
53.
50.
51.
55.
52.
60.
57.
56.
45.
35.
34.
46.
46.
38.
34.
35.
33.
34.
33.
35.
33.
34.
94~
17
.87
33.
40.
34.
34.
34.
36.
36.
43.
36.
34.
36.
35.
34.
37.
38.
37.
43.
45.
54.
iL f\
\y v
41 .
65.
54.
57.
6b.
59.
64.
b6.
62.
53.
47.
3b.
56.
50.
48.
39.
37.
34.
35.
34.
39.
34.
35.
35.
41.
35.
41.
35.
38.
39.
50.
38,
36.
38.
37.
35.
39.
40.
39.
48.
58.
60.
i. n
43.
68.
58.
60.
68.
64.
66.
70.
66.
56.
61.
41.
58.
52.
52.
50.
44.
3b.
36.
36.
41 .
35.
38.
47
-------
Table 4f. Sound Levels at Moose Measured by System A
JANUARY 15, 1978
DBS TIME LEQ L99 L90 L50 L10 L01 L.I LOO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
41
42
43
44
45
46
47
48
49
>UMM
O0:o0
00:30
01
01
02
02
03
03
04
04
05
05
06
06
07
07
08
08
09
09
10
10
11
11
12
12
13
13
14
14
15
15
16
16
17
17
18
18
19
19
20
20
21
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
u
:30
:00
:30
:00
21:30
22:00
22:30
23:00
23:30
IAR1
«:4«
33.072
33.238
33.037
33
33
33
33
33
33
32
33
32
33
33
34
34
35
35
33
33
33
43
40
47
31
35
33
34
36
48
33
44
48
34
32
32
32
32
32
32
33
.029
.165
.016
.526
.774
.015
.B95
.003
.857
.025
.725
.703
.307
.925
.253
.902
.655
.209
.105
.058
.002
.563
.552
.604
.901
.062
.906
.481
.490
.340
.780
.964
.876
.565
.381
.194
.538
.110
32.951
33.140
32.948
32.623
32.447
32.040
32.000
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
o.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
"7
0.
0.
0.
0.
0.
0.
0.
0.
0.
OBSERVATIONS
33.
33.
33.
33.
33.
33.
33.
33.
33.
32.
33.
32.
33.
33.
33.
33.
33.
33.
33.
33.
32.
32.
32.
32.
32.
32.
32.
32.
32.
33.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
AND
33.
33.
33.
33.
33.
33.
33.
34.
33.
33.
33.
33.
33.
33.
34.
34.
34.
34.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
34.
33.
33.
32.
32.
33.
33.
33.
32.
32.
J J .
32.
33.
33.
33.
33.
33.
32.
32.
32.
Leg
Ldn
33.
34.
33.
33.
34.
33.
33.
35.
33.
33.
33.
33.
33.
35.
36.
36.
37.
37.
35.
35.
34.
38.
3b.
41.
36.
36.
35.
35.
36.
37.
35.
39.
38.
33.
33.
33.
33.
32.
32.
^5
33.
34.
34.
33.
33.
33.
33.
32.
32.
38
" JO
= 41
34.
35.
34.
34.
35.
34.
39.
36.
34.
33.
33.
34.
34.
37.
38.
40.
45.
41 .
37.
37.
37.
57.
53.
61.
61.
46.
40.
45.
42.
44.
3ft.
58.
57.
35.
35.
35.
34.
34.
33.
3b.
38.
37.
34.
35.
33.
33.
33.
32.
.61
9 J 3
.46
35.
36.
34.
36.
37.
35.
43.
37.
34.
33.
35.
35.
34.
39.
42.
43.
49.
45.
41.
39.
41.
63.
61.
67.
75.
b2.
4b.
50.
55.
57.
41.
6b.
70.
bb.
42.
39.
34.
35.
34.
rttr-j
3B.
41.
41.
47.
38.
33.
34.
34.
32.
42.
37.
35.
37.
3b.
35.
46.
38.
3b.
34.
38.
36.
3b.
41 .
44.
46.
51.
53.
49.
46.
45.
60.
63.
b9.
bO.
bb.
51 .
b4.
bb.
«e.
bb.
bfi.
7b.
bb.
52.
44.
35.
41.
3V .
43.
43.
43.
51.
39.
34.
34.
34.
34.
48
-------
Table 4g. Sound Levels at Moose Measured by System A
JANUARY 16, 1978
DBS TIME LtQ L99 LyO L50 L10 LOl L.I LOO
1
2
3
4
5
b
1
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
00:
00;
01:
01:
02:
02:
03:
03:
04:
04:
05:
05:
06:
06:
07;
07:
08:
Ob:
09:
09:
10:
16:
17:
17:
18:
16:
19:
19:
20:
20:
21:
21:
22:
22:
23:
23:
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
32.
32.
32.
32.
32.
32.
32.
33.
33.
34.
36.
33.
40.
33.
32.
39.
37.
b5.
36.
35.
45.
44.
41.
35.
33.
32.
37.
37.
3B.
38.
39.
40.
3b.
36.
3B.
39.
237
529
031
OOl
013
019
015
559
633
787
164
332
574
022
149
179
751
240
216
930
765
089
252
440
499
939
«U
908
675
347
914
602
614
o40
161
513
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
o.
0.
32.
32.
32.
32.
32.
32.
32.
32.
32.
33.
32.
32.
32.
32.
32.
32.
32.
35.
32.
32.
34.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
33.
32.
33.
32.
33.
32.
32.
32.
32.
32.
32.
32.
32.
32.
33.
33.
33.
32.
32.
32.
34.
34.
44.
34.
33.
40.
37.
33.
34.
32.
32.
33.
34.
35.
33.
34.
35.
34.
34.
34.
35.
32.
33.
32.
32.
32.
32.
32.
33.
35.
36.
35.
34.
40.
34.
32.
3H.
40.
67.
39.
39.
48.
46.
38.
38.
35.
33.
41.
41 .
42.
41.
43.
44.
42.
39.
41.
43.
35.
36.
33.
32.
33.
33.
33.
42.
41.
43.
48.
38.
55.
40.
33.
49.
47.
78.
45.
44.
57.
57.
53.
42.
41.
40.
48.
48.
49.
49.
51.
51 .
49.
45.
49.
50.
40.
43.
33.
33.
33.
33.
33.
48.
44.
47.
54.
42.
60.
46.
35.
60.
54.
82.
49.
51 .
62.
61.
63.
47.
45.
47.
53.
53.
52.
54.
56.
54.
53.
49.
54.
5!S.
48.
45.
34.
33.
34.
33.
33.
53.
48.
50.
59.
43.
62.
51.
49.
62.
61.
85.
50.
56.
65.
64.
68.
48.
51.
51.
57.
54.
55.
59.
61 .
57.
59.
52.
57.
57.
SUMMAKY: 36 ObSEPVATIO^S AND LEQ = 49.95
49
-------
Table 4h. Sound Levels at Moose Measured by System A
DBS TIME
JANUARY 17, 1978
LKQ L99 L90 L50 LlO LOJ L.I LOO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
r J
24
25
26
27
28
29
30
31
32
33
34
J9
36
37
38
39
40
41
42
43
44
45
46
47
48
00
00
01
01
02
02
03
03
04
04
05
05
06
06
07
07
08
08
09
09
10
10
T
11
12
12
13
13
14
14
15
15
16
16
-r
17
18
18
19
19
20
20
21
21
22
22
23
23
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
. /\
:30
:00
:30
:00
:30
:oo
:30
:00
:30
:00
:30
:0v
-.30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
SUMMARY: 4
35.
35.
33.
36.
33.
33.
34.
32.
34.
36.
32.
33.
42.
33.
33.
40.
32.
37.
60.
36.
32.
43.
39.
34.
47.
48.
32.
40.
32.
34.
39.
33.
32.
32.
32.
32.
38.
32.
31.
31.
44.
36.
43.
32.
40.
243
196
607
347
255
466
713
749
997
714
759
274
724
581
273
095
527
303
526
898
560
129
676
028
219
513
253
668
676
197
230
452
224
216
117
134
449
062
979
987
375
619
650
608
245
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
V
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
o.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
8- OBSERVATIONS
33.
32.
32.
32.
32.
32.
32.
32.
32.
33.
32.
32.
33.
32.
32.
32.
32.
32.
33.
32.
31.
31.
31,
31.
31.
31.
30.
31.
31.
31.
31.
31.
31.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
AND
33.
33.
33.
33.
33.
33.
33.
33.
33.
34.
32.
32.
35.
33.
33.
33.
32.
34.
42.
34.
32.
32.
3f\
32.
31.
31.
31.
31.
31.
31.
31.
31.
31.
32.
30
32.
32.
32.
32.
32.
32.
32.
32.
33.
33.
32.
32.
32.
LEQ
Ldn
50
37.
36.
35.
39.
33.
34.
36.
33.
37.
39.
33.
34.
45.
35.
34.
36.
33.
40.
63.
41.
34.
36.
%A
41.
34.
41.
35.
33.
39.
32.
35.
35.
34.
33.
32.
32.
32.
33.
33.
32.
32.
32.
49.
37.
48.
32.
35.
jj
=
44.
45.
40.
46.
38.
40.
43.
36.
43.
46.
36.
40.
54.
40.
38.
53.
36.
48.
73.
45.
38.
59.
52.
44.
61.
39.
40.
54.
41.
44.
59.
53.
40.
Of)
34.
35.
33.
33.
52.
33.
32.
32.
56.
49.
56.
36.
54.
4-5.1+
f " 11
47.10
50.
51.
45.
51.
44.
45.
49.
40.
47.
49.
44.
45.
60.
44.
43.
62.
46.
54.
77.
48.
40.
63.
f , 1
58.
50.
67.
72.
45.
60.
49.
50.
65.
58.
50.
Ofi
43.
39.
38.
33.
59.
37.
32.
33.
58.
52.
57.
42.
61 .
56.
54.
48.
55.
51.
47.
55.
44.
53.
59.
52.
53.
63.
48.
45.
66.
53.
56.
80.
49.
46.
65.
feQ ,
62.
61.
71.
77.
49.
69.
54.
56.
67.
60.
57.
04-
48.
49.
45.
35.
62.
39.
32.
35.
59.
53.
59.
43.
62.
-------
Table 4i. Sound Levels at Moose Measured by System A
JANUARY 18, 1978
DBS TIME Lfiy L99 L90 L50 L10 LOl L.I 1.00
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
4B
00;
00;
01:
01:
02:
02:
03-
03:
04:
04;
05:
05:
06:
06;
07:
07;
08:
08:
09;
09:
10:
10:
11:
11:
12:
12:
13:
13:
14:
14:
15:
15:
16:
16:
17-
17:
18:
16:
19:
19-
20:
20:
21:
21:
22:
22:
23:
23:
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
00
30
33.
32.
36.
36.
33.
32.
32.
32.
32.
32.
33.
32.
32.
33.
33.
32.
34.
32.
32.
31 .
32.
39.
31.
32.
41.
45.
33.
42.
37.
32.
35.
45.
38.
33.
33.
37.
41 .
33.
34.
33.
41.
34.
33.
38.
33.
33.
34.
34.
b24
231
268
282
591
982
003
016
01 8
000
248
313
025
029
366
759
611
253
291
992
1^6
097
41B
556
0^3
029
992
080
08b
5bO
319
174
924
955
332
265
247
534
630
748
b20
075
397
713
316
108
127
335
0.
0.
0.
o.
o.
0.
o.
0.
o.
0.
0.
o.
0.
0.
o.
0.
0.
0.
o.
0.
o.
0.
o.
o.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
31.
31.
31.
31.
31.
31.
31.
31.
31.
31.
31.
31.
31.
32.
32.
32.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
33.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
32.
33.
32.
32.
32.
32.
31.
31.
31.
31.
31.
32.
31.
31.
31.
32.
33.
32.
33.
32.
32.
33.
33.
33.
33.
34.
34.
33.
33.
33.
33.
33.
34.
36.
32.
33.
35.
36.
34.
32.
32.
32.
32.
32.
32.
32.
34.
35.
34.
35.
33.
32.
32.
33.
3b.
31.
31.
43.
36.
35.
33.
39.
33.
34.
37.
35.
35.
34.
36.
34.
33.
35.
34.
41.
34.
34.
34.
34.
33.
34.
35.
38.
35.
50.
50.
41.
40.
32.
33.
33.
32.
42.
33.
33.
39.
40.
37.
42.
35.
36.
32.
36.
53.
34.
39.
53.
60.
44.
55.
49.
39.
46.
60.
53.
42.
41.
49.
56.
40.
43.
39.
56.
39.
38.
52.
37.
3t>.
41.
40.
40.
37.
55.
51.
42.
41.
33.
33.
33.
32.
4t>.
39.
33.
44.
43.
39.
45.
3b.
42.
35.
40.
56.
44.
50.
58.
66.
49.
65.
56.
47.
54.
66.
5b.
45.
45.
56.
62.
43.
49.
42.
5b .
42.
40.
54.
40.
38.
45.
44.
44.
39.
56.
52.
43.
42.
34.
34.
33.
33.
49.
59.
34.
45.
45.
42.
48.
44.
4b.
44.
42.
58.
49.
54.
64.
67.
52.
67.
59.
53.
58.
70.
60.
52.
53.
60.
63.
44.
59.
43.
59.
44.
41.
55.
41.
40.
51.
48.
SUMMARY: 48 OBSERVATIONS AND LEQ = 36.92
L,0 = 40.95
51
-------
Table 4j. Sound Levels at Moose Measured by System A
JANUARY 19, 1978
UBS TlMt Lty L99 L9U L50 LlO LOl L.I LOO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
IB
00
00
01
01
02
02
03
03
04
04
05
05
Ob
Oo
07
07
08
06
too
:30
:oo
:30
:00
:30
:00
:30
:00
:30
:00
:30
:00
:30
too
130
too
t30
35.
34.
43.
37.
34.
34.
34.
34.
3-*.
34.
35.
34.
57.
3V.
35.
34.
36.
35.
317
193
563
478
017
308
087
377
802
669
273
935
645
t>87
220
6b9
926
007
0.
0.
0.
0.
0.
0.
0.
0.
o.
0.
0.
0.
0.
0.
0.
0.
0.
0.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
34.
40.
35.
34.
34.
34.
34.
35.
34.
35.
34.
34.
35.
35.
34.
35.
35.
36.
34.
47.
41.
34.
35.
34.
35.
36.
36.
36.
36.
42.
43.
36.
35.
40.
36.
44.
38.
53.
47.
35.
35.
35.
36.
37.
37.
41.
40.
72.
50.
37.
37.
46.
39.
47.
41.
56.
49.
35.
35.
35.
36.
40.
38.
45.
44.
77.
55.
39.
40.
49.
41.
53.
41.
57.
51.
40.
36.
54.
39.
45.
45.
49.
50.
80.
58.
43.
43.
52.
43.
SUMMAHYt 18 OBSERVATIONS AND -LEQ = 45.65
52
-------
TABLE 5. DATA FROM SYSTEM B
en
CO
DATE & TIME (1978)
FROM
0111.1800
0111.2200
0112.0600
0112.1100
0112.2300
0113.0700
0113.1500
0113.2300
0114.0700
0114.1600
0114.2200
0115.0600
0116.1030
0116.2230
0117.0630
0117.1500
0117.2300
0118.0700
TO
0111.2200
0112.0600
0112.0900
0112.2300
0113.0700
0113.1100
0113.2300
0114.0700
0114.1500
0114.2200
0115.0600
0115.1400
0116.2230
0117.0630
0117.1030
0117.2300
0118.0700
0118.1500
PLACE
MORAN
MORAN
MORAN
MORAN
MORAN
MORAN
MOOSE
MOOSE
MOOSE
MOOSE
MOOSE
MOOSE
BEAVER CK
BEAVER CK
BEAVER CK
ELBOW #3
ELBOW #3
ELBOW #3
HOURS
4
8
3
12
8
4
8
8
8
6
8
8
12
8
4
8
8
8
Leq
31
24
25
31
22
26
_
-._
41
__
31
28
46
27
21
34
LID ax
61
__
46
62
(58)
(60)
»
--
78
<
__
60
47
72
57
45
62
L.01
52
38
40
53
35
43
63
35
63
56
38
63
50
41
66
47
39
51
Ll
43
30
37
43
27
36
48
30
51
41
32
49
42
38
59
39
32
47
LIO
32
22
26
30
21
27
35
27
35
30
28
32
33
32
44
25
19
37
L50
21
19
20
21
19
21
27
25
25
26
26
28
26
25
21
19
19
20
1-90
19
18
18
19
18
19
24
23
22
21
24
25
22
20
19
18
18
19
Lgg
18
18
18
18
18
18
22
22
21
19
23
24
20
19
19
18
18
18
l-min
18
18
18
17
18
18
20
21
20
18
22
22
19
19
18
18
18
18
-------
TABLE 6. Results of Brief Measurements
en
Site
Date
Time
Duration (min)
LO
LI
LIO
L50
L90
Lgg
Lmin
Temper at ure(°C)
Wind (km/h)
Mind Direction
Ground Cover
Topography
Vegetation
Site
Date
Time
Duration (min)
LO
L!
LIO
LBO
Lgo
Lgg
Lmin
Temperature(°C)
Mind (km/h)
Mind Direction
Ground Cover
Topography
Vegetation
1*
1/18/78
1302-1315
13
72
62
44
30
25
24
21
-4
0-5
Variable
Snow
Flat
Near decid-
uous trees
5b*
1/18/78
1050-1055
5
68
68
46
36
35
35
34
-1
0
Variable
Snow
Flat
Near decid-
uous trees;
river.
2
1/15/78
1254-1302
8
28
28
24
20
20
19
18
-4
0-5
Variable
Snow
Flat
None
5c
1/18/78
1106-1120
14
56
56
41
30
28
27
27
-1
0
Variable
Snow
Flat
None
3*
1/15/78
1055-1104
9
56
37
25
22
21
20
20
-2
3-11
North
Snow
Flat
Conif.
trees 60yds
6*
1/14/78
1145-1153
8
55
55
42
25
23
23
23
-3
8-11
North
Snow
Flat
None
4. a
1/14/78
1011-1018
7
32
32
28
25
23
22
22
-4
0-5
Variable
Snow
Flat
None
7*
1/19/78
1548-1605
17
45
40
30
25
22
20
20
-4
0
-.
Snow
Flat
Near conif-
erous trees.
4.b
1/17/78
1530-1541
11
40
40
26
24
22
21
20
-4
0-5
Variable
Snow
Flat
None
8
1/18/78
0936-0945
9
24
24
22
18
18
18
18
-2
0-11
Variable
Snow
Flat
None
4.c*
1/17/78
1808-1816
8
58
58
46
28
21
20
20
-4
0-5
Variable
Snow
Flat
None
9
1/19/78
1413-1425
12
35
35
29
26
24
22
22
-3
0
Snow
Flat
Near decid-
uous trees.
5. a
1/18/78
1035-1040
5
62
62
52
51
50
49
49
-1
0
Variable
Snow
Flat
Near dead
treesjriver
10*
1/18/78
1546-1556
10
39
36
30
25
19
19
18
-2
5-8
South
Snow
Flat
Sage brush
Mncludes aircraft noise
-------
APPENDIX. Wind-Induced and Instrumental Noise
When measuring low-level sounds, one must give more attention to
the effects of wind-induced noise and instrumental electronic noise
than when measuring high level sounds. Although the sound of the
breeze in the trees is an environmental sound that should be included
in any measurement of the background ambient, wind-induced noise is a
spurious sound that is generated in the microphone as a result of
interactions with flowing air; and, like the electronic noise in the
instrument, it serves only to mask the environmental sounds. The
problem is serious when the spurious sounds approach or exceed the
level of the sounds being measured.
Unfortunately, information on the wind response of particular
microphones is not plentiful. Figure 8 gives the expected combination
of wind-induced and electronic noise for a microphone of the type used
in System A. The curve is based on five datum points from the
manufacturer's literature and certain assumptions regarding curve shape
between points. The wind-induced noise values of Table 2 were taken
from this graph on the basis of average wind speeds. The true values
would undoubtedly be greater due to gusting and turbulence that are not
expressed by average wind speed. In fact, a review of the sound level
strip charts recorded during this survey revealed some apparent
wind-induced noise levels in excess of 60 dB.
Fortunately, wind-induced noise was relatively low during most of
this survey. Systems A and C were programmed to disregard any
measurements made when the wind speed exceeded 15 km/hr, but it is
interesting to note that half of the actual values of daily Leq during
the survey would have been exceeded by the microphone noise that a 15
km/hr wind would induce.
On many occasions it was so quiet and still that the instrument
readings represented electronic noise alone for extend periods. As
stated elsewhere, the respective A-weighted noise floors were as
follows:
System Noise Floor (dB)
A 32
B 18
C (1-in microphone) 24 - 25
C ( /2-in microphone) 31 - 33
D 18
55
-------
Sound level readings having values near the instrument's noise
floor cannot be taken at face value because they represent conbinations
of environmental noise with electronic noise and any wind-induced noise
that may be present. In effect, the instrument presents the level of
the sum of the apparent mean square sound pressures due to the
respective sources.
Figures 9 and 10 are intended to aid in the interpretation of sound
level meter readings which represent situations where the spurious
noises are significant. These graphs are useful only if all but one of
the variables are known or assumed. As an example problem using Figure
9, assume a reading of 29 dB where the instrument noise level is known
to be 25 dB. Find 29 dB on the ordinate (y-axis), find the point where
the 25 dB curve has that value/ and below that point read the
environmental-plus-wind-induced noise level on the abscissa (x-axis),
i.e., 27 dB.
It is noted that System A, with its noise floor about 14 dB above
that of System B, would provide values of Leq and L^ slightly higher
than would System B because of the electronic noise content. The
difference is appreciable only for values within a few decibels of the
noise floors. A simple hypothetical case illustrates the effect:
Assume that System A, with a noise floor of 32 dB, and System B, with
noise floor at 18 dB, are used to monitor for two days. The true Leq
due to environmental noise alone is 32 dB during the first day and 45
dB during the second. Each instrument would register an Leq equal to
the sum of true Leq plus its internal noise, assuming no wind-induced
noise were involved. The results would be as follows (shown to the
nearest 0.1 dB for purposes of illustration):
System A System B
Instrument noise (dB) 32.0 18.0
First day
True Leq (dB) 32.0 32.0
Reading (dB) 35.0 32.2
Second day
True Leq (dB) 45.0 45.0
Reading (dB) 45.2 45.0
56
-------
90
Fig. 8. EXPECTED WIND RESPONSE OF SYSTEM A
(Curve shape between points based on authors' assumptions.)
80
70
m
o
en
in
t-i
o
60
I
o
50
30
WIND-SPEED (km/hr)
J I L
10
20
30
40
50
60
70
80
-------
en
CO
44,-
40
36
20
16
8
Fig. 9. COMBINATION OF ENVIRONMENTAL, WIND-INDUCED, AND INSTRUMENT NOISE
INSTRUMENT NOISE = 32 dB
(System C with 1 in microphone)
INSTRUMENT NOISE = 25 dB
(System C with 1 in microphone)
INSTRUMENT NOISE = 18 dB
(System B)
ENVIRONMENTAL NOISE COMBINED WITH WIND-INDUCED NOISE (dB)
12
16
20
24
28
32
36
40
44
-------
Fig.10. COMBINATION OF ENVIRONMENTAL, WIND-INDUCED, AND INSTRUMENT NOISE
90
80
70
60
50
40
30
20
10
90 dB-
80
WIND-INDUCED NOISE COMBINED WITH INSTRUMENT NOISE
0+0=3
1 I
ENVIRONMENTAL NOISE (dB)
i i i i L
10
20 30 40 50
60 70
80
GPO 884-388
59
------- |