ACOUSTIC STUDY OF THE SUNY CANTON WIND TURBINE CANTON, NEW YORK. June 2013

Transcription

1 ACOUSTIC STUDY OF THE SUNY CANTON WIND TURBINE CANTON, NEW YORK June 2013

2 ACOUSTIC STUDY OF THE SUNY CANTON WIND TURBINE CANTON, NEW YORK Prepared for: Sustainable Energy Developments, Inc. 317 Route 104 Ontario, NY Prepared by: Tech Environmental, Inc. 303 Wyman Street, Suite 295 Waltham, MA June 26, 2013

3 TABLE OF CONTENTS Section Contents Page 1.0 EXECUTIVE SUMMARY COMMON MEASURES OF COMMUNITY SOUND NOISE REGULATIONS AND CRITERIA New York State Department of Environmental Conservation Town of Canton Regulations AMBIENT SOUND LEVEL AND WIND MEASUREMENTS CALCULATED FUTURE SOUND LEVELS Methodology Results and Conclusions...12 APPENDIX A CADNA ACOUSTIC MODEL OUTPUT....A-1 ii

4 1.0 EXECUTIVE SUMMARY An acoustic study was performed for the proposed wind turbine on the SUNY Canton Campus, in Canton NY. The proposed turbine is a Vestas V100 rated at 1.8 MW and will have a 80 meter hub height. Existing sound levels on the project site, and sound levels at the nearest on-campus housing, were measured during a 14-day period from May 16, 2013 through May 30, The study s conclusions are as follows: Existing background L EQ sound levels during times when winds are high enough to support wind turbine operation are generally in the range of 39 to 51 dba. An analysis of the minimum L EQ sound levels found them to range from 39.2 dba for the turbine cut-in wind speed of 3 m/s (6.7 mph) to 48.2 dba for the turbine design wind speed of 9.8 m/s (21.9 mph). All wind speed values are at hub height. The ambient sound levels used for the DEC compliance analysis are therefore 39.2 dba for cut-in wind conditions and 48.2 dba for the design wind conditions. The DEC Noise Guidelines limit the increase in the ambient sound level to no more than 6 dba. The V100 model reaches its maximum sound power level at a wind speed of 9.8 m/s (21.9 mph), and at this wind speed, the ambient sound level used for compliance analysis is 48.2 dba. The study results are conservative for three reasons: 1) Turbine vendor-guaranteed maximum sound power levels, plus a 2-dBA uncertainty factor, were assumed; 2) The acoustic model assumed favorable sound propagation with a ground-based temperature inversion, such as occurs on a clear night; and 3) winter frozen ground conditions were assumed with no attenuation from trees or vegetation. Wind turbine outdoor sound levels at the closest on-campus building to the east will be 31.7 to 42.9 dba and will increase ambient sound levels by 0.7 to 1.5 dba. All predicted sound level increases are in compliance with the DEC noise guidelines. The wind turbine outdoor sound levels at cut-in and design wind speeds at the closest off-campus residence to the west will be 27.6 and 38.8 dba, and will increase ambient sound levels by 0.3 to 0.6 dba. All predicted sound level increases are in compliance with the DEC noise guidelines. In summary, the V100 wind turbine proposed at the SUNY Canton campus fully complies with the NYSDEC Noise Guidelines. Compliance with this guideline provides a reasonable basis for concluding the wind project will not create a nuisance. 1

5 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 person s ears as sound waves, which are minute variations in air pressure. The loudness of a sound depends on the sound pressure level 1, which has units of 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. Every 10-dB increase is perceived as a doubling of loudness. Most sounds we hear in our daily lives have sound pressure levels in the range of 30 db to 85 db. A property of the decibel scale is that the numerical values of two separate sounds do not directly add. 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) on the decibel scale, not a doubling to 140 db. In terms of sound perception, 3 db increase is the minimum change most people can detect. 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; 3 db is the minimum perceptible change for broadband sounds, i.e. sounds that include all frequencies. Typical sound levels associated with various activities and environments are presented in Table 1. The existing sound levels at a wind energy project site are determined primarily by the proximity to roads and highways (the source of traffic noise) and by the wind speed (the source of wind turbulence noise in trees and vegetation). 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 and correlates well with people s perception of loudness. There is also a C-weighting scale that was designed for exposure to very loud sounds, namely those over 85 decibels. 2 It is important to use the correct A-weighting scale in wind turbine sound studies where the audible sounds are in the low range of 25 to 45 decibels. If instead, for example, one applied the C-weighting scale, such an inappropriate choice would artificially inflate low-frequency sound and would not represent how wind turbine sounds are heard. 1 The sound pressure level is defined as 20*log 10 (P/P o ) where P is the sound pressure and P o is the reference pressure of 20 micro-pascals (20 μpa), which by definition corresponds to 0 db. 2 Bolt, Beranek, and Newman, Inc., Handbook of Noise Ratings, NASA-CR-2376, April 1974, page 21. 2

6 The level of most sounds change from moment to moment. Some are sharp impulses lasting one 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 equivalent sound level L eq 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 energy-average sound level and it includes in its measure all of the sound we hear. EPA has determined that the L eq average sound level correlates best with how people perceive and react to sound. 3 Sound pressure level measurements typically include an analysis of the sound spectrum into its various frequency components to determine tonal characteristics. The unit of frequency is Hertz (Hz), measuring the cycles per second of the sound pressure waves. In the physiology of human hearing, every octave jump of a tone corresponds to a doubling of the sound frequency in Hz. For example, Middle-C on a piano has a frequency of approximately 260 Hz. High-C, one octave above, has a frequency of approximately 520 Hz. The hearing range for most people is 20 Hz to 20,000 Hz. In acoustic studies, the sound spectrum is divided into octave bands with center frequencies that are an octave apart, specifically the bands centered on 16 Hz, 31.5 Hz, 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, 8000 Hz, and Hz. Sound power level is on a decibel scale 4, leading to possible confusion since sound power (energy density) and sound pressure (what we hear) are not the same. An acoustic model uses the sound power level of a wind turbine along with other assumptions to calculate the sound pressure level heard at a receiver located a certain distance from the wind turbine. 3 U.S. Environmental Protection Agency, Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety, Publication EPA-550/ The sound power level is defined as 10*log 10 (W/W o ), where W is the sound power of the source in Watts and W o is the reference power of Watts. 3

7 TABLE 1 VARIOUS INDOOR AND OUTDOOR SOUND LEVELS Sound Sound Pressure Level Outdoor Sound Levels (μpa) _(dba) _ Indoor Sound Levels 6,324, Rock Band at 5 m Jet Over-Flight at 300 m ,000, Inside New York Subway Train Gas Lawn Mower at 1 m , Food Blender at 1 m Diesel Truck at 15 m - 85 Noisy Urban Area--Daytime 200, Garbage Disposal at 1 m - 75 Shouting at 1 m Gas Lawn Mower at 30 m 63, Vacuum Cleaner at 3 m Suburban Commercial Area - 65 Normal Speech at 1 m Quiet Urban Area -- Daytime 20, Quiet Conversation at 1m Quiet Urban Area--Nighttime 6, Dishwasher Next Room - 45 Suburban Area--Nighttime 2, Empty Theater or Library - 35 Rural Area--Nighttime Quiet Bedroom at Night - 25 Empty Concert Hall Rustling Leaves Average Whisper - 15 Broadcast and Recording Studios Human Breathing Reference Pressure Level 20-0 Threshold of Hearing Notes: μpa - Micropascals describe sound pressure levels (force/area). dba - A-weighted decibels describe sound pressure on a logarithmic scale with respect to 20 μpa. 4

8 3.0 NOISE REGULATIONS AND CRITERIA 3.1 New York State Department of Environmental Conservation The New York State Department of Environmental Conservation (NYSDEC) issued a program guidance document entitled Assessing and Mitigating Noise Impacts on February 2, The guidance discusses various aspects of noise and suggested steps for performing noise assessments. Further, it provides suggestions on evaluating significant increases in noise levels. The guidance notes that an increase in ambient noise of 10 dba is perceived by the majority of people to be a doubling of the loudness of a sound. For example, if the ambient sound level is 50 dba, and is then increased to 60 dba, most people would perceive the new sound level as twice as loud. The guidance recommends that for non-industrial settings, the A-weighted sound pressure level should probably not exceed the ambient level, which NYSDEC defines as the L eq sound level, by more than 6 dba at a given receptor. The addition of any sound source in a non-industrial setting should not raise the total future ambient noise level above a maximum of 65 dba. This would be considered the upper end limit, since 65 dba allows for undisturbed speech at a distance of approximately three feet. Sound levels in industrial or commercial areas should not exceed 79 dba. 3.2 Town of Canton Regulations Town of Canton s Town Code, Article VI, Section B. Alternative Energy Systems. Section 70-33B of the Town Code states that Applicants for building permits for alternate energy systems shall indicate the potential effect on neighboring properties from noise, odor, aesthetic, health or safety considerations of the system. Since there is no quantitative sound limits, Tech is proposing that the wind turbine A-weighted sound pressure level not exceed the measured ambient L eq level by more than 6 dba. For the purposes of this study, the L eq sound levels were also used to represent ambient sound levels to determine compliance with the NYDEC noise guidelines. 5

9 4.0 AMBIENT SOUND LEVEL AND WIND MEASUREMENTS The proposed wind turbine will be located on the southern portion of the athletic fields west of Cornell Drive, north of Route 68 on land owned by SUNY Canton. North of the project are athletic fields owned by the College. West of the project are undeveloped lands and some off-campus residences. To the south of the project is wooded landed and Route 68, and to the east of the project are SUNY Canton classrooms, offices, and on-campus housing units. The long-term sound monitor was placed near the proposed turbine location to the west of Cornell Drive. The long-term sound monitoring location provided representative ambient sound levels for all residential areas surrounding the proposed wind turbine. This monitoring station also provided a conservative estimate of ambient sound levels for the residential areas to the west of the project because those residential areas are closer to Route 68 than the sound monitor location. Figure 1 illustrates the location of the proposed wind turbine, long term sound monitoring station, and the receptor locations used for acoustic modeling, designated R-1 through R-5. Wind speeds at a height of 33 feet were obtained from the National Weather Service meteorological tower at Potsdam Airport in Potsdam, NY and extrapolated to the 80-m hub height using a wind shear coefficient of This coefficient was provided by AWS True Power. The wind speed data are presented along with the sound level measurements from the long-term monitoring station in Figure 2. Long-term sound level monitoring was performed over a ten day period from Thursday, May 16, 2013 at 4 p.m. through Wednesday, May 29, 2013 at 1 p.m. to document 10-minute sound levels, day and night, over a range of wind conditions. Hub height wind speeds were at or above the turbine cut-in speed (3.0 m/s) for about half of the ten day period. When the long-term monitoring station was set up, skies were cloudy, the temperature was 68 0 F, and ground level winds were mph. There were a six days where a short duration rain shower occurred and general rain on the 24 th and 26 th during the 14 day period, typical of May weather. The audible sounds during the time the long term meter was setup were wind through the trees, some on-campus activities, and natural sounds such as birds and insects. 5 downloaded January 30,

10 setup were wind through the trees, some on-campus activities, and natural sounds such as birds and insects. The sound level measurements were taken with a Larson Davis Model 831 real-time sound level analyzer, equipped with precision condenser microphones having an operating range of 5 db to 140 db, and an overall frequency range of 3.5 to 20,000 Hz. This meter meets or exceeds all requirements set forth in the American National Standards Institute (ANSI) Standards for Type 1 for quality and accuracy. Prior to and immediately following the measurement sessions, the sound analyzer was calibrated (no level adjustment was required) with an ANSI Type 1 calibrator which has an accuracy traceable to the National Institute of Standards and Technology (NIST). All instrumentation was laboratory calibrated per ANSI recommendations. For the measurement session, the microphone was fitted with an environmental windscreen to negate wind noise and mounted at a height of 2 meters above grade. Measurements were made away from any vertical reflecting surfaces in compliance with ANSI Standard S The 10-minute L EQ sound level measurements (dba) and 10-minute average hub height wind speeds in meters per second (m/s) for the long-term monitoring station were assembled into a spreadsheet and the data were sorted into wind speed bins centered about integer values of the hub height wind speed. For the V100 turbine, the cut-in and design wind speeds at hub height are 3 m/s and 9.8 m/s, respectively. Wind speed bins ranged from 3 m/s to 11 m/s. The 4 m/s bin includes all periods with average wind speeds in the range or 3.5 to 4.4 m/s; the 5 m/s bin contains all periods with wind speeds in the range of 4.5 to 5.4 m/s, and so forth, with the last bin spanning 10.5 to 11.4 m/s. The L EQ values exceeded 90% of the time by the other L EQ values in each wind speed bin have been highlighted in Figure 2 and a linear regression line has been fit to those values. Since this series of L EQ values for the bins exhibit a lot of variability, the ambient sound levels actually used in the acoustic study were taken from the smoothed regression line of best fit. This ensures the ambient level is a monotonically increasing function of wind speed. 6 Acoustical Society of America, ANSI Standard S /Part 2, Quantities and Procedures for Description and Measurement of Environmental Sound. Part 2: Measurement of Long-Term Wind-Area Sound. 7

11 The series of hub height wind speeds for which the manufacturer has published sound power levels under International Standard IEC were input to the regression line equation to obtain the corresponding ambient sound levels; these are presented in Table 2. TABLE 2 SOUND POWER AND SITE-SPECIFIC LEQ SOUND LEVELS FOR A VESTAS V100 TURBINE, 80-M HUB HEIGHT Hub Height Wind Speed (m/s) IEC Turbine Sound Power Level (dba) Project Site (dba) * * *No sound power level data published below 4.2 m/s, conservatively utilized the value at this higher wind speed. The ambient sound level at the cut-in wind speed of 3 m/s is 35.9 dba, and the ambient sound level at the design wind speed of 9.8 m/s is 48.2 dba. 7 Vestas, General Specification V MW VCSS, section , November 23,

12 Legend R-4!. # 0 Long Term Sound Monitoring Location!? Wind Turbine Modeling Receptor Location R-1 R-3 Proposed Turbine Location R-5 R-2 Long Term Sound Monitor ± 0 Figure 1 Sound Monitoring and Receptor Locations for the SUNY Canton Wind Turbine Canton, NY ,000 Feet

13 80 Figure 2 Average 10-Minute Hub Height Windspeed vs. L EQ Sound Level - Canton, NY 70 L EQ Sound Level (dba) y = x R 2 = Windspeed vs. 10-Minute LEQ 90th Percentile LEQ Within Bin Linear (90th Percentile LEQ Within Bin) Average Hub Height Wind Speed (m/s)

14 5.0 CALCULATED FUTURE SOUND LEVELS 5.1 Methodology Future sound levels from the wind turbine at the nearest inhabited structures and residences 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 Atmospheric absorption, the process by which sound energy is absorbed by the air, was calculated using ANSI S Absorption of sound assumed standard day conditions and is significant at large distances. Ground surfaces were assumed to be mixed ground consisting of both hard and porous (vegetated) surfaces. 10 This is a reasonable worst-case assumption and approximates winter frozen ground conditions in the area between the turbine and the nearest residences to the east and west. No attenuation from trees or vegetation was assumed. Digital terrain heights were extracted from New York State GIS. The model assumes favorable sound propagation as occurs with a ground-based temperature inversion, such as might occur on a clear night. At other times, atmospheric turbulence and wind shadow effects will reduce sound levels by 5 to 20 dba from those presented below. For the V MW turbine, the cut-in wind speed at which the turbine begins operation is a hub height wind speed of 3 m/s or 6.7 mph, and at cut-in the V100 has a sound power level of 93.8 dba. The maximum sound power level of 105 dba is reached before the design wind speed, at a hub height wind speed of 9.8 m/s or 21.9 mph. An uncertainty K-factor of 2.0 dba was added to these sound power levels to account for uncertainty in sound power measurements and variations in turbine manufacturing (IEC Technical Specification ). Thus, the maximum modeled sound power level was 107 dba. 8 International Standard, ISO , Acoustics Attenuation of Sound During Propagation Outdoors, -- Part 2 General Method of Calculation. 9 American National Standards Institute, ANSI S , American National Standard Method for the Calculation of the Absorption of Sound by the Atmosphere, Ground absorption factor G set equal to 0.5 in Cadna-A. 11

15 5.2 Results and Conclusions Figures 3 and 4 show color-coded decibel contours (5 feet above ground level) for operation of the V100 wind turbine at the cut-in wind speed and design wind speeds, respectively. Note that these figures assume the sound receiving location is always downwind of the wind turbine, and the figures present a composite worst-case in which all locations are simultaneously downwind of the wind turbine. Model output is provided in Appendix A. The acoustic modeling results for the wind turbine are summarized in Tables 3 through 7, which provide the highest predicted turbine sound level at the nearest sensitive receivers, and the maximum increase in the ambient sound level under the NYSDEC Noise Guidelines, for seven operating levels from the cut-in to the design wind speed. The maximum sound levels were predicted at the closest inhabited buildings to the east and west. Wind turbine outdoor sound levels at the closest on-campus building to the east will be 31.7 to 42.9 dba and will increase ambient sound levels by 0.7 to 1.5 dba. The wind turbine outdoor sound levels at cut-in and design wind speeds at the closest off-campus residence to the west will be 27.6 and 38.8 dba, and will increase ambient sound levels by 0.3 to 0.6 dba. All predicted sound level increases are in compliance with the DEC noise guidelines. Predicted octave band sound levels confirm the project will not create any pure tones. In summary, the V100 wind turbine proposed for the SUNY Canton property fully complies with both the New York State DEC Noise Guidelines noise limits. Compliance with this guideline provides a reasonable basis for concluding the wind project will not create a nuisance. 12

16 TABLE 3 NYSDEC COMPLIANCE ANALYSIS FOR RECEPTOR 1 CLOSEST ON-CAMPUS BUILDING #1 TO THE EAST (dba) Hub Height Wind Speed (m/s) Ambient L EQ Level Maximum Project Sound Future Ambient Level Net Increase Note: Town Noise Policy limits the increase in the ambient level to 6 dba. TABLE 4 NYSDEC COMPLIANCE ANALYSIS FOR RECEPTOR 2 CLOSEST ON-CAMPUS BUILDING #2 TO THE EAST (dba) Hub Height Wind Speed (m/s) Ambient L EQ Level Maximum Project Sound Future Ambient Level Net Increase Note: Town Noise Policy limits the increase in the ambient level to 6 dba. 13

17 TABLE 5 NYSDEC COMPLIANCE ANALYSIS FOR RECEPTOR 3 CLOSEST OFF-CAMPUS RESIDENCE #1 TO THE WEST (dba) Hub Height Wind Speed (m/s) Ambient L EQ Level Maximum Project Sound Future Ambient Level Net Increase Note: Town Noise Policy limits the increase in the ambient level to 6 dba. TABLE 6 NYSDEC COMPLIANCE ANALYSIS FOR RECEPTOR 4 CLOSEST OFF-CAMPUS RESIDENCE #2 TO THE WEST (dba) Hub Height Wind Speed (m/s) Ambient L EQ Level Maximum Project Sound Future Ambient Level Net Increase Note: Town Noise Policy limits the increase in the ambient level to 6 dba. 14

18 TABLE 7 NYSDEC COMPLIANCE ANALYSIS FOR RECEPTOR CLOSEST ON-CAMPUS HOUSING TO THE EAST (dba) Hub Height Wind Speed (m/s) Ambient L EQ Level Maximum Project Sound Future Ambient Level Net Increase Note: Town Noise Policy limits the increase in the ambient level to 6 dba. 15

19 Legend!? Wind Turbine Sound Levels 35 dba 40 dba 45 dba ± 0 Figure 3 Maximum Sound Levels from the SUNY Canton Wind Turbine at Cut-In Wind Speed Canton, NY ,000 1,500 Feet

20 Legend!? Wind Turbine Sound Levels 35 dba 40 dba 45 dba 50 dba 55 dba ± 0 Figure 4 Maximum Sound Levels from the SUNY Canton Wind Turbine at Design Wind Speed Canton, NY ,000 1,500 Feet

21 APPENDIX A ACOUSTIC MODEL OUTPUT A-1

22 Cadna Modeling Results Vestas V100 Turbine Canton, NY Receptor Results, Turbine at 3.0 m/s (cut-in) Hub Height Windspeed Name ID Sound Height Coordinates Level X Y Z (dba) Closest Campus Building r Closest Campus Building r Closest Off Campus Residence r Closest Off Campus Residence r Closest On-Campus Housing r Receptor Results, Turbine at 4.2 m/s Hub Height Windspeed Name ID Sound Height Coordinates Level X Y Z (dba) Closest Campus Building r Closest Campus Building r Closest Off Campus Residence r Closest Off Campus Residence r Closest On-Campus Housing r Receptor Results, Turbine at 5.6 m/s Hub Height Windspeed Name ID Sound Height Coordinates Level X Y Z (dba) Closest Campus Building r Closest Campus Building r Closest Off Campus Residence r Closest Off Campus Residence r Closest On-Campus Housing r Receptor Results, Turbine at 7.0 m/s Hub Height Windspeed Name ID Sound Height Coordinates Level X Y Z (dba) Closest Campus Building r Closest Campus Building r Closest Off Campus Residence r Closest Off Campus Residence r Closest On-Campus Housing r

23 Cadna Modeling Results Vestas V100 Turbine Canton, NY Receptor Results, Turbine at 8.4 m/s Hub Height Windspeed Name ID Sound Height Coordinates Level X Y Z (dba) Closest Campus Building r Closest Campus Building r Closest Off Campus Residence r Closest Off Campus Residence r Closest On-Campus Housing r Receptor Results, Turbine at 9.8 m/s Hub Height Windspeed Name ID Sound Height Coordinates Level X Y Z (dba) Closest Campus Building r Closest Campus Building r Closest Off Campus Residence r Closest Off Campus Residence r Closest On-Campus Housing r Receptor Results, Turbine at 11.2 m/s Hub Height Windspeed Name ID Sound Height Coordinates Level X Y Z (dba) Closest Campus Building r Closest Campus Building r Closest Off Campus Residence r Closest Off Campus Residence r Closest On-Campus Housing r