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Appendix N
Noise Reports
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ACOUSTIC STUDY OF THE
GALLOO ISLAND WIND TURBINES
HOUNSFIELD, NEW YORK
October 2009
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ACOUSTIC STUDY OF THE
GALLOO ISLAND WIND TURBINES
HOUNSFIELD, NEW YORK
Prepared for:
American Consulting Professionals of New York, PLLC70 Niagara Street, Suite 410
Buffalo, NY 14202
and
Watertown Development of NY LLC950-A Union Road, Suite 20
West Seneca, NY 14224-3454
Prepared by:
Tech Environmental, Inc.
303 Wyman Street, Suite 295l h A 02451
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TableofContents
1.0 EXECUTIVE SUMMARY .............................................................................................. 12.0 COMMON MEASURES OF COMMUNITY SOUND ................................................... 33.0 NOISE GUIDELINES AND CRITERIA ......................................................................... 5
3.1 State Noise Guidelines ............................................................................................ 53.2 Audibility and Pure Tones ....................................................................................... 63.2 Audibility and Pure Tones ....................................................................................... 7
4.0 AMBIENT SOUND LEVEL MEASUREMENTS .......................................................... 85.0 CALCULATED FUTURE SOUND LEVELS ................................................................. 9
5.1 Methodology ........................................................................................................... 95.2 Modeling Results at Shoreline Locations .............................................................. 105.3 Low Frequency Analysis at Shoreline Locations .................................................. 115.4 Modeling Results for Worker Housing ................................................................. 13
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1.0 EXECUTIVE SUMMARY
Watertown Development of NY, LLC proposes to locate 84 Vestas V90 3.0 MW wind turbines on
Galloo Island in eastern Lake Ontario more than 7 miles from the mainland. To respond to comments
collected for the Draft Environmental Impact Statement, an assessment was done of the projects sound
effects to: 1) the nearest mainland locations (Lyme, New York), and 2) the on-island housing for the
workers who will maintain the wind turbines on Galloo Island. Tech Environmental (TE) performed a
study of the sound effects from the wind farm on the nearest shoreline locations including South Shore
Road Extension in Lyme, Beach Road in Lyme, Flanders Road in Lyme, Fox Island Road on Fox
Island, and Pillar Point in Brownsville. Ambient sound levels from a similar offshore wind project, the
Cape Wind Project, were used to estimate the Leq1 ambient sound levels at the five shoreline receptors.
These data were approved by the NYS DEC for use on this project. To ensure a conservative analysis,
only the quieter off-shore wind measurements from the Cape Wind project for an isolated location withno boat or motor vehicle noise (Point Gammon, Yarmouth) were utilized. The criteria used for the
shoreline locations of the mainland were the NYS DEC incremental sound guidelines and potential
audibility.
To protect employees on the island, TE also studied the projects sound effects on the outdoor
environment at the workers residential buildings that will be built on Galloo Island. The criterion for
this employee effects portion of the study was the OSHA hearing conservation action level of 85 dBA.
This is a conservative threshold since hearing protection for workers is not required except when sound
levels exceed 90 dBA.
Future sound levels from the Galloo Island wind turbines were calculated with the Cadna/A acoustic
model. Cadna/A is a sophisticated 3-D model for sound propagation and attenuation based on
International Standard ISO 9613. Predicted maximum sound levels are conservative because: 1) The
model was instructed to ignore foliage sound absorption; 2) The model assumes partial reflection from
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when sound propagation is most favorable, but wind turbine operation is least likely; and 5) The
turbine maximum sound power level includes a 2-dBA safety margin.
The studys conclusions are as follows:
The maximum predicted wind farm sound levels at the five closest shoreline receptors are only14.3 to 32.5 A-weighted decibels (dBA) and far below the minimum ambient sound level of
50.7 dBA associated with the turbine design wind condition (9 m/s wind speed at hub height).
The maximum increase in the ambient sound level at the shoreline is only 0.1 dBA and wellwithin the NYS DEC-recommended 6-dBA threshold.
Analysis of the broadband and octave band sound levels reveals that the wind farm will not beaudible at any shoreline location, and there will be no perceptible infrasound or very low
frequency sound from the Galloo Island wind farm.
The predicted maximum outdoor sound level at the worker housing area on Galloo Island is58.1 dBA and safely in compliance with the OSHA hearing conservation action level of 85
dBA. An outdoor sound level of 58 dBA is typical for an urban area and will not interfere withoutdoor activities at the worker residential buildings. A wind turbine outdoor sound level of 58
dBA is less than the 65 dBA level that is typical for a conversation between two people
standing a few feet apart.
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2.0 COMMON MEASURES OF COMMUNITY SOUND
All sounds originate with a source a human voice, vehicles on a roadway, or an airplane overhead.
The sound energy moves from the source to a persons ears as sound waves, which are minute
variations in air pressure. The loudness of a sound depends on the sound pressure level, defined as the
ratio of two pressures: the measured sound pressure from the source divided by a reference pressure
(the quietest sound we can hear). The unit of sound pressure is the decibel (dB). The decibel scale is
logarithmic to accommodate the wide range of sound intensities to which the human ear is subjected.
On this scale, the quietest sound we can hear is 0 dB, while the loudest is 120 dB. Most sounds we
hear in our daily lives have sound pressure levels in the range of 30 dB to 100 dB.
A property of the decibel scale is that the sound pressure levels of two separate sounds are added the
result is not simply the numerical sum. For example, if a sound of 70 dB is added to another sound of70 dB, the total is only a 3-decibel increase (or 73 dB), not 140 dB. In terms of the human perception
of sound, a halving or doubling of loudness requires changes in the sound pressure level of about 10
dB; for broadband sounds, 3 dB is the minimum perceptible change.
Sound exposure in a community is commonly expressed in terms of the A-weighted sound level
(dBA); A-weighting approximates the frequency response of the human ear. Levels of many sounds
change from moment to moment. Some are sharp impulses lasting 1 second or less, while others rise
and fall over much longer periods of time. There are various measures of sound pressure designed for
different purposes. The Leq, or equivalent sound level, is the steady-state sound level over a period of
time that has the same acoustic energy as the fluctuating sounds that actually occurred during that same
period. It is commonly referred to as the average broadband sound level. This is the metric which
New York State Department of Environmental Conservation (NYS DEC) uses to establish ambient
sound levels. The Lmax, or maximum sound level, represents the one second peak level experienced
during a given time period Sound level measurements typically include an analysis of the sound
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TABLE 1
COMMON INDOOR AND OUTDOOR SOUND LEVELS
Outdoor Sound Levels
Sound
Pressure
(Pa)
Sound
Level
(dBA)Indoor Sound Levels
6,324,555 110 Rock Band at 5 m
Jet Over-Flight at 300 m 105
2,000,000 100 Inside New York Subway Train
Gas Lawn Mower at 1 m 95
632,456 90 Food Blender at 1 m
Diesel Truck at 15 m 85
Noisy Urban Area Daytime 200,000 80 Garbage Disposal at 1 m
75 Shouting at 1 m
Gas Lawn Mower at 30 m 63,246 70 Vacuum Cleaner at 3 m
Suburban Commercial Area 65 Normal Speech at 1 m
20,000 60
Quiet Urban Area Daytime 55 Quiet Conversation at 1 m
6,325 50Quiet Urban Area Nighttime 45
2,000 40 Empty Theater or Library
Quiet Suburb Nighttime 35
632 30 Quiet Bedroom at Night
Quiet Rural Area Nighttime 25 Empty Concert Hall
Rustling Leaves 200 20 Average Whisper15 Broadcast and Recording Studios
63 10
5 Human Breathing
Reference Pressure Level 20 0 Threshold of Hearing
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3.0 NOISE GUIDELINES AND CRITERIA
3.1 State Noise Guidelines
The New York State Department of Environmental Conservation (NYS DEC) uses a noise guideline
document2 to assess noise impacts under the State Environmental Quality Review (SEQR) process.
The Guideline states The Leq
value provides an indication of the effects of sound on people. It is also
useful in establishing the ambient sound level at a potential noise source Appropriate receptor
locations may be either at the property line of the parcel upon which the facility is located or at the
location of use or inhabitance on adjacent property.3 The Guideline goes on to say In non-industrial
settings the [sound pressure level] SPL should probably not exceed ambient noise by more than 6 dBA
at the receptor, but also notes There may be occasions where an increase in SPLs of greater than 6
dBA might be acceptable. The addition of any noise source, in a non-industrial setting, should not
raise the ambient noise level above a maximum of 65 dBA.4 For this project, the NYS DEC Leq
guideline was applied at the closest off-island shoreline receptors with residential land use, shown in
Figure 1:
South Shore Road Extension, Town of Lyme Beach Road, Town of Lyme Flanders Road, Town of Lyme Fox Island Road, Fox Island Pillar Point, Town of Brownsville
The results of the analysis are presented in Sections 5.2 and 5.3. In addition, the OSHA hearing
conservation action level5
of 85 dBA was applied to the worker housing area for the project on
Galloo Island. The OSHA assessment results are presented in Section 5.4.
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N
Figure 1
Sound Modeling LocationsGalloo Island Wind Farm
GALLOO ISLAND
Pillar Point
Fox Island Road
Flanders Road
Beach Road
South Shore Road Extension
Stony Island
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3.2 Audibility and Pure Tones
According to ANSI Standards, an audible pure tone occurs when the 1/3-octave band in a sound power
spectrum is higher than the numerical mean of the two adjacent bands by 5 to 15 dB, with the threshold
of 5 dB corresponding to high frequencies (> 500 Hz) and the 15-dB threshold corresponding to low
frequencies (< 125 Hz).6 Application of the ANSI definition to the sound power spectrum for the
Vestas V90 wind turbines reveals there are no audible pure tones produced by the wind turbines.
A 3-dBA increase in sound is the threshold of perceptibility and occurs when a new sound source is
exactly equal to the existing average (Leq) sound level. Thus, when a new sound source produces a
sound pressure level that is below the existing sound level, the new sound source will not be audible
unless it produces a pure tone. Since a new sound source is likely to have a different spectrum from
the background noise, the threshold for audibility is more difficult to quantify. A study done for theNational Park Service
7established that aircraft flying over the Grand Canyon, which has very low
background sound levels, first became audible when the aircraft sound was 8 dBA below the average
background level (Leq), and the audibility occurred at that low of a level because of the tonal character
of the aircraft noise. The Vestas wind turbines do not have the tonal characteristics of an aircraft, thus
the audibility threshold for the wind turbine sound is somewhere between 0 and 8 dBA below the
existing Leq sound level. For this study, an audibility threshold of 5 dBA below the Existing Leq level
was assumed.
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4.0 AMBIENT SOUND LEVEL MEASUREMENTS
Ambient sound levels from a similar offshore wind project, the Cape Wind Project,8 were used to
estimate the Leq ambient sound levels at the five shoreline receptors listed in Section 3.1. These data
were approved by the NYS DEC for use on this project for the EIS review.9
To ensure a conservative
analysis, only the quieter off-shore wind measurements from the Cape Wind project for an isolated
location with no boat or motor vehicle noise (Point Gammon, Yarmouth) were utilized. A two-week
monitoring program during the months of November and December revealed a minimum Leq sound
level of 50.7 dBA during off-shore winds that were at the turbine design wind speed, a minimum Leq
sound level of 60.8 dBA during on-shore winds at the design wind speed, and a minimum Leq sound
level of 46.5 dBA during light winds corresponding to the turbine cut-in wind speed. This analysis
was done for the maximum turbine sound power level, which first occurs at the design wind speed.
Thus, the selected ambient Leq sound level is 50.7 dBA. When winds are on-shore to the shorelinereceptors, ambient sound levels will be about 10 dBA higher than the ambient level assumed in this
analysis, adding conservatism to the results. When winds are off-shore, the wind shadow effect will
reduce shoreline sound levels by 20 dBA from those presented in this study. Thus, the coupling of the
off-shore ambient sound level with acoustic modeling that assumes on-shore sound propagation
produces a very conservative result.
Under the cut-in wind speed condition, the V90 sound power level is 6 dBA less than the maximum
sound power level. The minimum ambient sound level for the cut-in wind condition is about 4 dBA
less than that for the design wind condition. Thus, in terms of incremental impact, the design wind
condition that is analyzed in this study represents the worst case.
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5.0 CALCULATED FUTURE SOUND LEVELS
5.1 Methodology
Future sound levels from the Galloo Island wind turbines were calculated with the Cadna/A acoustic
model. Cadna/A is a sophisticated 3-D model for sound propagation and attenuation based on
International Standard ISO 961310. Atmospheric absorption, the process by which sound energy is
absorbed by the air, was calculated using ANSI S1.26-1995.11
Cadna/A models sound assumingreceptors in all directions simultaneously downwind. Absorption of sound assumed standard day
conditions, and it is significant at large distances. The model parameters were set as follows: receiver
height of 1.2 meters, ground absorption G=0.5 (mixed ground partial reflection) for the land areas,
and G=0.0 (reflective surface) for the surface of Lake Ontario. Note that the land on Galloo Island is
undeveloped and actually has a soft ground surface, for which G is 1.0.
The model built in an additional level of conservatism over estimating the actual sound power level
generated by the project turbines; the maximum sound power level established in the IEC 61400-11
test is 109.4 dBA for a hub height wind speed of 9 m/s or higher.12 A safety margin of 2 dBA was
added to this and the resulting maximum sound power level of 111.4 dBA was used in the acoustic
modeling for the V90 wind turbine. A total of 84 V90 wind turbines operating simultaneously on
Galloo Island (252 MW rated capacity) were modeled with Cadna/A assuming an 80-meter hub height.
Predicted maximum sound levels are conservative because: 1) The model was instructed to ignore
foliage sound absorption; 2) The model assumes partial reflection from soft ground surfaces which
typically absorb sound; 3) The model assumes Lake Ontario is a perfectly reflective surface; 4) The
acoustic model assumes a ground-based temperature inversion, such as those that may occur on calm,
clear nights when sound propagation is most favorable but wind turbine operation is least likely; and 5)
The turbine maximum sound power level includes a 2-dBA safety margin.
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5.2 Modeling Results at Shoreline Locations
The maximum predicted wind farm sound levels at the five closest shoreline receptors are 14.3 to 32.5
dBA and are compared in Table 2 to the ambient sound levels. The project is consistent with the NYS
DEC Guideline because the maximum increase in the ambient Leq sound level is 0.1 dBA at the
closest receptors and within the DEC-recommended 6-dBA threshold. In addition, the project will be
inaudible at these locations because the maximum sound level is more than 5 dBA below the ambient
level and the turbines do not produce a pure tone. Figure 2 presents color contours of the maximum
sound levels assuming all locations are downwind of the wind farm and experiencing maximum sound
propagation.
TABLE 2
MAXIMUM PROJECT SOUND LEVELS
AT THE CLOSEST SHORELINE LOCATIONS
IN LYME AND BROWNSVILLE (dBA)
Shoreline
Receptor
Ambient
Leq Level
MaximumProject
Sound
CombinedSound
Level
Net
Increase
South Shore Road Ext., Lyme 50.7 32.5 50.8 0.1
Beach Road, Lyme 50.7 30.0 50.7
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5.3 Low Frequency Analysis at Shoreline Locations
The acoustic modeling includes the very low frequency 1/3-octave bands of 16 Hz and 20Hz.
Under high wind conditions (20 mph and above), research has shown that refraction due to wind
gradients causes a transition from standard hemispherical to slower cylindrical wave spreading at a
downwind distance of approximately 2 km for infrasound (sound waves with a frequency below 20
Hz) with normal hemispherical wave spreading for all higher frequency bands.13
This refinement
was included in the acoustic model.
The potential for low frequency noise impacts was first assessed as follows. Using the sound
power spectra, the broadband sound power for both A-weighting and C-weighting scales were
calculated as 111.4 dBA and 129.8 dBC, respectively. The (dBC-dBA) difference of 18.4 was then
compared to a 20 decibel threshold that is often used as a first check on whether a turbine mayproduce low-frequency noise. The V90 frequency spectrum does not suggest a low frequency
noise problem. The acoustic modeling results also reveal that the wind turbines will not be audible
at the nearest off-island receptors.
To further address low frequency concerns, the frequency spectrum of predicted maximum sound
levels at the five shoreline receptors are graphed in Figure 3 through 7, along with the full range of
ambient sound levels corresponding to the design wind condition and the threshold of human
hearing. The ambient sound levels range from Leq 50.7 dBA (minimum) to Leq 66.5 dBA
(maximum) when the hub height wind speed is near the design wind speed value of 9 m/s. The
figures confirm there is no 1/3-octave band pure tone. The wind turbine spectrum has its highest
energy in the range of 31.5 to 50 Hz where there is a plateau in the spectrum that is within or below
the range of ambient sound levels and therefore will not be audible. The frequency graphs also
reveal that low frequency sound for the wind turbines in the five lowest 1/3-octave bands will be
below the threshold of human hearing
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To check for infrasound14 impacts, the lowest three 1/3-octave band sound levels predicted from
project operation are compared in Table 3 to the human hearing threshold. In the two lowest frequency
bands (16 and 20 Hz), the maximum project sound levels will be at least 34 dB below the human
hearing threshold. Thus, there will be no perceptible infrasound or very low frequency sound from the
Galloo Island wind farm.
TABLE 3
COMPARISON OF PREDICTED VERY LOW FREQUENCY SOUND LEVELS
AT THE CLOSEST SHORELINE LOCATIONS IN LYME AND BROWNSVILLE
TO HUMAN HEARING THRESHOLDS (dB)
Shoreline
Receptor
16 Hz 1/3-
Octave Band
20 Hz 1/3-
Octave Band
25 Hz 1/3-
Octave Band
Human Hearing Threshold 92.0 84.0 76.0
South Shore Road Ext., Lyme 57.6 49.4 48.9
Beach Road, Lyme 56.8 47.5 47.0
Flanders Road, Lyme 57.0 47.9 47.4
Fox Island Road, Fox Island 55.4 46.1 45.6
Pillar Point, Brownsville 43.9 33.0 32.5
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5.4 Modeling Results for Worker Housing
The criterion for this employee effects portion of the study was the OSHA hearing conservation action
level of 85 dBA. This is a conservative threshold since hearing protection for workers is not required
except when sound levels exceed 90 dBA. The predicted maximum sound level at the worker housing
area on Galloo Island is 58.1 dBA and safely in compliance with the OSHA action level of 85 dBA.
An outdoor sound level of 58 dBA is typical for an urban area and will not interfere with outdoor
activities at the worker residential buildings. A wind turbine outdoor sound level of 58 dBA is less
than the 65 dBA level that is typical for a conversation between two people standing a few feet apart
(see Table 1).
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N
Figure 2
Maximum Sound Levels (dBA) at the Shoreline
Galloo Island Wind Farm
Key
= 30 dBA
= 35 dBA
= 40 dBA
= 45 dBA
= 50 dBA
= 55 dBA
= 60 dBA
South Shore Road Extension
Flanders Road
Beach Road
Fox Island Road
Worker Housing
Pillar Point
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0
10
20
30
40
50
60
70
80
90
100
Leq
SoundPres
sureLevel(dBr
e20
PA)
1/3 Octave Band Frequency (Hz)
FIGURE 3. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT SOUTH SHORE ROAD EXT., LYME FOR THE DESIGN WIND SPEED
Highest Baseline Level Leq
Lowest Baseline Level Leq
Threshold of Human Hearing
Maximum ContinuousWind Park Sound 66.5
50.7
32.5
16 20 25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1K 1.25K 1.6K 2K 2.5K 3.15K 4K 5K 6.3K 8K 10K 12.5K 16K A-wtd
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0
10
20
30
40
50
60
70
80
90
100
Leq
SoundPres
sureLevel(dBr
e20
PA)
1/3 Octave Band Frequency (Hz)
FIGURE 4. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT BEACH ROAD, LYME FOR THE DESIGN WIND SPEED
Highest Baseline Level Leq
Lowest Baseline Level Leq
Threshold of Human Hearing
Maximum ContinuousWind Park Sound 66.5
50.7
30.0
16 20 25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1K 1.25K 1.6K 2K 2.5K 3.15K 4K 5K 6.3K 8K 10K 12.5K 16K A-wtd
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0
10
20
30
40
50
60
70
80
90
100
Leq
SoundPres
sureLevel(dBr
e20
PA)
1/3 Octave Band Frequency (Hz)
FIGURE 5. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT FLANDERS ROAD, LYME FOR THE DESIGN WIND SPEED
Highest Baseline Level Leq
Lowest Baseline Level Leq
Threshold of Human Hearing
Maximum ContinuousWind Park Sound 66.5
50.7
30.5
16 20 25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1K 1.25K 1.6K 2K 2.5K 3.15K 4K 5K 6.3K 8K 10K 12.5K 16K A-wtd
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0
10
20
30
40
50
60
70
80
90
100
Leq
SoundPres
sureLevel(dBr
e20
PA)
1/3 Octave Band Frequency (Hz)
FIGURE 6. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT FOX ISLAND ROAD, FOX ISLAND FOR THE DESIGN WIND SPEED
Highest Baseline Level Leq
Lowest Baseline Level Leq
Threshold of Human Hearing
Maximum ContinuousWind Park Sound 66.5
50.7
28.6
16 20 25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1K 1.25K 1.6K 2K 2.5K 3.15K 4K 5K 6.3K 8K 10K 12.5K 16K A-wtd
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0
10
20
30
40
50
60
70
80
90
100
Leq
SoundPres
sureLevel(dBr
e20P
A)
1/3 Octave Band Frequency (Hz)
FIGURE 7. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT PILLAR POINT, BROWNSVILLE FOR THE DESIGN WIND SPEED
Highest Baseline Level Leq
Lowest Baseline Level Leq
Threshold of Human Hearing
Maximum ContinuousWind Park Sound 66.5
50.7
14.3
16 20 25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1K 1.25K 1.6K 2K 2.5K 3.15K 4K 5K 6.3K 8K 10K 12.5K 16K A-wtd
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ACOUSTIC STUDY OF THE GALLOO ISLAND
WIND TURBINES, HOUNSFIELD, NEW YORK
SOUND IMPACTS ON STONY ISLAND, NY
October 2009
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ACOUSTIC STUDY OF THE GALLOO ISLANDWIND TURBINES, HOUNSFIELD, NEW YORK
SOUND IMPACTS ON STONY ISLAND, NY
Prepared for:
American Consulting Professionals of New York, PLLC70 Niagara Street, Suite 410
Buffalo, NY 14202
and
Watertown Development of NY LLC
950-A Union Road, Suite 20West Seneca, NY 14224-3454
Prepared by:
Tech Environmental, Inc.
303 Wyman Street, Suite 295
Waltham, MA 02451
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TableofContents
1.0 EXECUTIVE SUMMARY .............................................................................................. 12.0 COMMON MEASURES OF COMMUNITY SOUND ................................................... 23.0 NOISE GUIDELINES AND CRITERIA ......................................................................... 4
3.1 State Noise Guidelines ............................................................................................ 43.2 Audibility and Pure Tones ....................................................................................... 6
4.0 AMBIENT SOUND LEVEL MEASUREMENTS .......................................................... 75.0 CALCULATED FUTURE SOUND LEVELS ................................................................. 8
5.1 Methodology ........................................................................................................... 85.2 Modeling Results ..................................................................................................... 95.3 Low Frequency Analysis ....................................................................................... 10
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1.0 EXECUTIVE SUMMARY
Watertown Development of NY, LLC proposes to locate 84 Vestas V90 3.0 MW wind turbines on
Galloo Island in eastern Lake Ontario more than 7 miles from the mainland. Tech Environmental
performed a study of the sound effects from the wind farm on the shoreline of Stony Island, which lies
3.5 miles to the east of Galloo Island. Ambient sound levels from a similar offshore wind project, the
Cape Wind Project, were used to estimate the Leq ambient sound levels at the Stony Island shoreline
receptor. These data were approved by the NYS DEC for use on this project. To ensure a conservativeanalysis, only the quieter off-shore wind measurements from the Cape Wind project for an isolated
location with no boat or motor vehicle noise (Point Gammon, Yarmouth) were utilized.
Future sound levels from the Galloo Island wind turbines were calculated with the Cadna/A acoustic
model. Cadna/A is a sophisticated 3-D model for sound propagation and attenuation based on
International Standard ISO 9613. Predicted maximum sound levels are conservative because: 1) The
model was instructed to ignore foliage sound absorption; 2) The model assumes partial reflection from
soft ground surfaces which typically absorb sound; 3) The model assumes Lake Ontario is a perfectly
reflective surface and ignores the effects of waves in scattering sound waves; 4) The acoustic model
assumes a ground-based temperature inversion, such as those that may occur on calm, clear nights
when sound propagation is most favorable but wind turbine operation is least likely; and 5) The turbine
maximum sound power level includes a 2-dBA safety margin.
The studys conclusions are as follows:
The maximum predicted wind farm sound level at Stony Island is only 40.6 A-weighteddecibels (dBA) and far below the minimum ambient sound level of 50.7 dBA associated withthe turbine design wind condition (9 m/s wind speed at hub height).
The maximum increase in the ambient sound level at Stony Island is only 0.4 dBA and wellwithin the NYS DEC recommended 6 dBA threshold
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2.0 COMMON MEASURES OF COMMUNITY SOUND
All sounds originate with a source a human voice, vehicles on a roadway, or an airplane overhead.
The sound energy moves from the source to a persons ears as sound waves, which are minute
variations in air pressure. The loudness of a sound depends on the sound pressure level, defined as the
ratio of two pressures: the measured sound pressure from the source divided by a reference pressure
(the quietest sound we can hear). The unit of sound pressure is the decibel (dB). The decibel scale is
logarithmic to accommodate the wide range of sound intensities to which the human ear is subjected.On this scale, the quietest sound we can hear is 0 dB, while the loudest is 120 dB. Most sounds we
hear in our daily lives have sound pressure levels in the range of 30 dB to 100 dB.
A property of the decibel scale is that the sound pressure levels of two separate sounds are added the
result is not simply the numerical sum. For example, if a sound of 70 dB is added to another sound of
70 dB, the total is only a 3-decibel increase (or 73 dB), not 140 dB. In terms of the human perception
of sound, a halving or doubling of loudness requires changes in the sound pressure level of about 10
dB; for broadband sounds, 3 dB is the minimum perceptible change.
Sound exposure in a community is commonly expressed in terms of the A-weighted sound level
(dBA); A-weighting approximates the frequency response of the human ear. Levels of many sounds
change from moment to moment. Some are sharp impulses lasting 1 second or less, while others rise
and fall over much longer periods of time. There are various measures of sound pressure designed for
different purposes. The Leq, or equivalent sound level, is the steady-state sound level over a period of
time that has the same acoustic energy as the fluctuating sounds that actually occurred during that same
period. It is commonly referred to as the average broadband sound level. This is the metric which
New York State Department of Environmental Conservation (NYS DEC) uses to establish ambient
sound levels. The Lmax, or maximum sound level, represents the one second peak level experienced
during a given time period Sound level measurements typically include an analysis of the sound
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TABLE 1
COMMON INDOOR AND OUTDOOR SOUND LEVELS
Outdoor Sound Levels
Sound
Pressure
(Pa)
Sound
Level
(dBA)Indoor Sound Levels
6,324,555 110 Rock Band at 5 m
Jet Over-Flight at 300 m 1052,000,000 100 Inside New York Subway Train
Gas Lawn Mower at 1 m 95
632,456 90 Food Blender at 1 m
Diesel Truck at 15 m 85
Noisy Urban Area Daytime 200,000 80 Garbage Disposal at 1 m
75 Shouting at 1 m
Gas Lawn Mower at 30 m 63,246 70 Vacuum Cleaner at 3 m
Suburban Commercial Area 65 Normal Speech at 1 m
20,000 60
Quiet Urban Area Daytime 55 Quiet Conversation at 1 m
6,325 50
Quiet Urban Area Nighttime 45
2,000 40 Empty Theater or Library
Quiet Suburb Nighttime 35
632 30 Quiet Bedroom at Night
Quiet Rural Area Nighttime 25 Empty Concert Hall
Rustling Leaves 200 20 Average Whisper
15 Broadcast and Recording Studios
63 10
5 Human Breathing
Reference Pressure Level 20 0 Threshold of Hearing
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3.0 NOISE GUIDELINES AND CRITERIA
3.1 State Noise Guidelines
The New York State Department of Environmental Conservation (NYS DEC) uses a noise guideline
document1 to assess noise impacts under the State Environmental Quality Review (SEQR) process.
The Guideline states The Leq value provides an indication of the effects of sound on people. It is also
useful in establishing the ambient sound level at a potential noise source Appropriate receptor
locations may be either at the property line of the parcel upon which the facility is located or at the
location of use or inhabitance on adjacent property.2 The Guideline goes on to say In non-industrial
settings the [sound pressure level] SPL should probably not exceed ambient noise by more than 6 dBA
at the receptor, but also notes There may be occasions where an increase in SPLs of greater than 6
dBA might be acceptable. The addition of any noise source, in a non-industrial setting, should not
raise the ambient noise level above a maximum of 65 dBA.3 For this project, the NYS DEC Leq
guideline was applied at the closest off-island shoreline receptor on Stony Island, shown in Figure 1.
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N
Figure 1
Sound Modeling Location
Galloo Island Wind Farm
GALLOO ISLAND
Stony Island
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3.2 Audibility and Pure Tones
According to ANSI Standards, an audible pure tone occurs when the 1/3-octave band in a sound power
spectrum is higher than the numerical mean of the two adjacent bands by 5 to 15 dB, with the threshold
of 5 dB corresponding to high frequencies (> 500 Hz) and the 15-dB threshold corresponding to low
frequencies (< 125 Hz).4 Application of the ANSI definition to the sound power spectrum for the
Vestas V90 wind turbines reveals there are no audible pure tones produced by the wind turbines.
A 3-dBA increase in sound is the threshold of perceptibility and occurs when a new sound source is
exactly equal to the existing average (Leq) sound level. Thus, when a new sound source produces a
sound pressure level that is below the existing sound level, the new sound source will not be audible
unless it produces a pure tone. Since a new sound source is likely to have a different spectrum from
the background noise, the threshold for audibility is more difficult to quantify. A study done for the
National Park Service5
established that aircraft flying over the Grand Canyon, which has very low
background sound levels, first became audible when the aircraft sound was 8 dBA below the average
background level (Leq), and the audibility occurred at that low of a level because of the tonal character
of the aircraft noise. The Vestas wind turbines do not have the tonal characteristics of an aircraft, thus
the audibility threshold for the wind turbine sound is somewhere between 0 and 8 dBA below the
existing Leq sound level. For this study, an audibility threshold of 5 dBA below the Existing Leq level
was assumed.
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4.0 AMBIENT SOUND LEVEL MEASUREMENTS
Ambient sound levels from a similar offshore wind project, the Cape Wind Project,6
were used toestimate the Leq ambient sound levels at the Stony Island shoreline receptor. These data were
approved by the NYS DEC for use on this project for the EIS review.7
To ensure a conservative
analysis, only the quieter off-shore wind measurements from the Cape Wind project for an isolated
location with no boat or motor vehicle noise (Point Gammon, Yarmouth) were utilized. A two-week
monitoring program during the months of November and December revealed a minimum Leq sound
level of 50.7 dBA during off-shore winds that were at the turbine design wind speed, a minimum Leq
sound level of 60.8 dBA during on-shore winds at the design wind speed, and a minimum Leq sound
level of 46.5 dBA during light winds corresponding to the turbine cut-in wind speed. This analysis
was done for the maximum turbine sound power level, which first occurs at the design wind speed.
Thus, the selected ambient Leq sound level is 50.7 dBA. When winds are on-shore to the shoreline
receptors, ambient sound levels will be about 10 dBA higher than the ambient level assumed in this
analysis, adding conservatism to the results. When winds are off-shore, the wind shadow effect will
reduce shoreline sound levels by 20 dBA from those presented in this study. Thus, the coupling of the
off-shore ambient sound level with acoustic modeling that assumes on-shore sound propagation
produces a very conservative result.
Under the cut-in wind speed condition, the V90 sound power level is 6 dBA less than the maximum
sound power level. The minimum ambient sound level for the cut-in wind condition is about 4 dBA
less than that for the design wind condition. Thus, in terms of incremental impact, the design wind
condition that is analyzed in this study represents the worst case.
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5.0 CALCULATED FUTURE SOUND LEVELS
5.1 Methodology
Future sound levels from the Galloo Island wind turbines were calculated with the Cadna/A acoustic
model. Cadna/A is a sophisticated 3-D model for sound propagation and attenuation based on
International Standard ISO 96138. Atmospheric absorption, the process by which sound energy is
absorbed by the air, was calculated using ANSI S1.26-1995.9 Cadna/A models sound assuming
receptors in all directions simultaneously downwind. Absorption of sound assumed standard day
conditions, and it is significant at large distances. The model parameters were set as follows: receiver
height of 1.2 meters, ground absorption G=0.5 (mixed ground partial reflection) for the land areas,
and G=0.0 (reflective surface) for the surface of Lake Ontario. Note that the land on Galloo Island is
undeveloped and actually has a soft ground surface, for which G is 1.0.
The model built in an additional level of conservatism over estimating the actual sound power level
generated by the project turbines; the maximum sound power level established in the IEC 61400-11
test is 109.4 dBA for a hub height wind speed of 9 m/s or higher.10 A safety margin of 2 dBA was
added to this and the resulting maximum sound power level of 111.4 dBA was used in the acoustic
modeling for the V90 wind turbine. A total of 84 V90 wind turbines operating simultaneously on
Galloo Island (252 MW rated capacity) were modeled with Cadna/A assuming an 80-meter hub height.
Predicted maximum sound levels are conservative because: 1) The model was instructed to ignore
foliage sound absorption; 2) The model assumes partial reflection from soft ground surfaces which
typically absorb sound; 3) The model assumes Lake Ontario is a perfectly reflective surface; 4) The
acoustic model assumes a ground-based temperature inversion, such as those that may occur on calm,
clear nights when sound propagation is most favorable but wind turbine operation is least likely; and 5)
The turbine maximum sound power level includes a 2-dBA safety margin.
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5.2 Modeling Results
The maximum predicted wind farm sound level at the Stony Island shoreline receptor is 40.6 dBA andis compared in Table 2 to the ambient sound level. The project is consistent with the NYS DEC
Guideline because the maximum increase in the ambient Leq sound level is 0.4 dBA at the closest
receptor and within the DEC-recommended 6-dBA threshold. In addition, the project will be inaudible
at this location because the maximum sound level is more than 5 dBA below the ambient level and the
turbines do not produce a pure tone. Figure 2 presents color contours of the maximum sound levels
assuming all locations are downwind of the wind farm and experiencing maximum sound propagation.
TABLE 2
MAXIMUM PROJECT SOUND LEVEL
AT THE CLOSEST STONY ISLAND SHORELINE LOCATION (dBA)
Shoreline
Receptor
Ambient
Leq Level
Maximum
Project
Sound
Combined
Sound
Level
Net
Increase
Stony Island southwest shoreline 50.7 40.6 51.1 0.4
Note: NYS DEC Guideline limits the increase in the ambient level to 6 dBA for residential areas.
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5.3 Low Frequency Analysis
The acoustic modeling includes the very low frequency 1/3-octave bands of 16 Hz and 20Hz. Under
high wind conditions (20 mph and above), research has shown that refraction due to wind gradients
causes a transition from standard hemispherical to slower cylindrical wave spreading at a downwind
distance of approximately 2 km for infrasound (sound waves with a frequency below 20 Hz) with
normal hemispherical wave spreading for all higher frequency bands.11 This refinement was included
in the acoustic model.
The potential for low frequency noise impacts was first assessed as follows. Using the sound power
spectra, the broadband sound power for both A-weighting and C-weighting scales were calculated as
111.4 dBA and 129.8 dBC, respectively. The (dBC-dBA) difference of 18.4 was then compared to a
20 decibel threshold that is often used as a first check on whether a turbine may produce low-frequency
noise. The V90 frequency spectrum does not suggest a low frequency noise problem. The acoustic
modeling results also reveal that the wind turbines will not be audible at the nearest off-island
receptors.
To check for infrasound12 impacts, the lowest three 1/3-octave band sound levels predicted from
project operation are compared in Table 3 to the human hearing threshold. In the two lowest frequency
bands (16 and 20 Hz), the maximum project sound levels will be at least 29 dB below the human
hearing threshold. Thus, there will be no perceptible infrasound or very low frequency sound from the
Galloo Island wind farm.
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TABLE 3
COMPARISON OF PREDICTED VERY LOW FREQUENCY SOUND
LEVELS AT THE CLOSEST STONY ISLAND SHORELINE LOCATION
(dB)
ShorelineReceptor
16 Hz 1/3-Octave
Band
20 Hz 1/3-Octave
Band
25 Hz 1/3-Octave
Band
Human Hearing Threshold 92.0 84.0 76.0
Stony Island southwest
shoreline60.0 55.0 54.5
Key
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N
Figure 2
Maximum Sound Levels (dBA) at Stony Island
Galloo Island Wind Farm
= 30 dBA
= 35 dBA
= 40 dBA
= 45 dBA
= 50 dBA
= 55 dBA
= 60 dBA