galloo island wind turbine noise dec noise guidelines

8/6/2019 Galloo Island Wind Turbine noise Dec Noise Guidelines

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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


4/38

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


8/38

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



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


15/38

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


16/38

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).


18/38

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


20/38

0

10

20

30

40

50

60

70

80

90

100

Leq

SoundPres

sureLevel(dBr

e20

PA)


FIGURE 4. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT BEACH ROAD, LYME FOR THE DESIGN WIND SPEED





50.7

30.0



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0

10

20

30

40

50

60

70

80

90

100

Leq

SoundPres

sureLevel(dBr

e20

PA)


FIGURE 5. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT FLANDERS ROAD, LYME FOR THE DESIGN WIND SPEED





50.7

30.5



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0

10

20

30

40

50

60

70

80

90

100

Leq

SoundPres

sureLevel(dBr

e20

PA)


FIGURE 6. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT FOX ISLAND ROAD, FOX ISLAND FOR THE DESIGN WIND SPEED





50.7

28.6



23/38

0

10

20

30

40

50

60

70

80

90

100

Leq

SoundPres

sureLevel(dBr

e20P

A)


FIGURE 7. MAXIMUM CONTINUOUS SOUND LEVEL FROM PROJECT OPERATIONAT PILLAR POINT, BROWNSVILLE FOR THE DESIGN WIND SPEED





50.7

14.3



24/38

ACOUSTIC STUDY OF THE GALLOO ISLAND

WIND TURBINES, HOUNSFIELD, NEW YORK

SOUND IMPACTS ON STONY ISLAND, NY

October 2009


25/38

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


26/38

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


27/38

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.



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


28/38

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


29/38

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


30/38

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.


31/38

N

Figure 1

Sound Modeling Location


GALLOO ISLAND

Stony Island


32/38

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



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


= 30 dBA

= 35 dBA

= 40 dBA

= 45 dBA

= 50 dBA

= 55 dBA

= 60 dBA

galloo island wind turbine noise dec noise guidelines

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