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HomeMy WebLinkAboutAcoustic-Modeling-Report-February-192014.pdf ACOUSTIC STUDY OF THE BLACK OAK WIND FARM ENFIELD, NEW YORK February 2014 ACOUSTIC STUDY OF THE BLACK OAK WIND FARM ENFIELD, NEW YORK Prepared for: Black Oak Wind Farm, LLC 863 Hayts Road Ithaca, NY 14850 Prepared by: Tech Environmental, Inc. 303 Wyman Street, Suite 295 Waltham, MA 02451 Certified by Peter H. Guldberg, INCE, CCM and Ryan T. Callahan, INCE, EIT Revised February 19, 2014 TABLE OF CONTENTS Section Contents Page 1.0 EXECUTIVE SUMMARY ..................................................................................................1  2.0 COMMON MEASURES OF COMMUNITY SOUND ......................................................3  3.0 NOISE REGULATIONS AND CRITERIA ........................................................................7  3.1 Local Wind Energy Facilities Law .............................................................................7  3.2 State Noise Guidelines and Ambient Sound Levels ...................................................7  4.0 CALCULATED FUTURE SOUND LEVELS ....................................................................9  4.1 Methodology ...............................................................................................................9  4.2 Sound Level Contour Map ........................................................................................10  4.3 Maximum Sound Levels at Occupied Structures ......................................................10  4.4 Low Frequency Sound, Vibration and Tonality .......................................................12  4.5 Infrasound and Health Effects ..................................................................................13  APPENDIX A -ACOUSTIC MODELING FOR GE 1.7-100 TURBINES..............A-1 ii 1.0 EXECUTIVE SUMMARY Black Oak Wind Farm, LLC proposes to build a wind energy project with a nominal 12-MW capacity in Enfield, New York. This revised report presents maximum sound levels for the GE 1.7-100 (1.7- MW) wind turbine at a 96-meter hub height. The design wind speed, defined as the hub height wind speed at which maximum sound power is first produced is 10 m/s for the GE 1.7-100 turbine1. Existing sound levels were measured at three long-term and four short-term monitoring stations covering the project area in April 2011. A presentation and analysis of the baseline sound level measurements is provided in a separate report.2 Future sound levels at residences and lands within the Black Oak project area were calculated with the Cadna/A acoustic model in accordance with International Standard ISO 9613-2. The Black Oak Wind Farm was analyzed with all turbines operating at design capacity. The acoustic modeling results are conservative due to the following assumptions: 1. All wind turbines were assumed to be operating simultaneously. 2. All wind turbine sound power levels correspond to the IEC 61400-11 maximum sound power level plus an uncertainty factor. 3. The acoustic model assumed the most favorable conditions for sound propagation, corresponding to a ground-based temperature inversion, such as might occur on a calm, clear night, or during a downwind condition. 4. No attenuation from trees or other vegetation was assumed. 5. Winter frozen ground conditions were assumed for minimal ground absorption. 6. Excess attenuation from wind shadow effects and daytime air turbulence were ignored. A color coded decibel contour map was produced (Figure 2), and sound levels were predicted at all occupied structures in the project area. This study’s conclusions are as follows: 1 GE Energy Proprietary Data, GE 1.7-100, sound power level curve, February 14, 2014. 2  The Enfield Wind Energy Facilities Local Law sets a sound limit of 60 A-weighted decibels (dBA) at the nearest Non-Participating residence.  The New York State Department of Environmental Conservation (NYS DEC) uses a Noise Guideline to assess noise impacts under the SEQRA process. The Guideline recommends the sound pressure level from a new project should probably not exceed the Leq ambient level by more than 6 dBA at a receptor, such as a Non-Participating residence. The Guideline also states that the addition of a new source, in a non-industrial setting, should not raise the ambient noise level above a maximum of 65 dBA. The Guideline is not an enforceable regulatory limit, and the NYS DEC Guideline is used solely to judge whether sound levels are at a level to require further analysis or mitigation.  A separate baseline sound measurement study has established the ambient sound level for a wide range of wind conditions. The Leq sound measurements were analyzed to identify those time periods: (1) for which hub-height wind speeds were at least 10 m/s, at or approaching the design speed at which the turbines will produce maximum sound power, and (2) for which there was no measurable precipitation. The overall Leq sound level across all monitoring locations and hours was 39.8 dBA. This measured ambient level is 5 dBA less than the suggested 45 dBA ambient level in the NYS DEC Noise Guideline for “a seemingly serene setting such as rural farm land,” a description that fits Enfield. Following the NYS DEC Guideline and adding 6 dBA, the project goal for non-participating residences is therefore a sound level no higher than 45.8 dBA, rounded down to 45 dBA. This is not an enforceable regulatory limit.  Predicted maximum sound levels at all residences are well below 60 dBA and thus the project, designed with the GE 1.7-100 turbines will fully comply with the sound limit in the Enfield Wind Energy Facilities Law.  For the GE 1.7-100 turbine, there are just three receptors with a maximum predicted sound level above 45 dBA, and the highest maximum sound level at an occupied residence is 45.9 dBA at Receptor 14. We recommend that the receptors with levels higher than 45 be made Participants in the project.  There are no receptors with a low-frequency sound level above 65 dB in the 31.5 Hz or 63 Hz octave bands. Low frequency sound from Black Oak Wind Farm will not cause annoyance or noticeable vibrations in building elements at any nearby receptors.  Measurements of existing conditions reveal that naturally-occurring low-frequency octave band levels are in the range of 62 to 80 un-weighted decibels (dB) for the 31.5 Hz and 63 Hz bands. Whereas the maximum wind farm low frequency sound levels at any occupied residence are typically lower, it can be concluded that Black Oak Wind Farm will not expose people, wildlife, or livestock to low frequency sound levels higher than those already occurring in the natural environment of Enfield, and the wind farm’s sound therefore does not pose a risk to these individuals. 2 HMMH, “Noise Study for Black Oak Wind Farm,” March 9, 2012. 3 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 level3, 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 90 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 is the minimum change most people can detect. Table 1 describes the subjective effect of different changes in sound levels. TABLE 1 SUBJECTIVE EFFECT OF CHANGES IN SOUND PRESSURE LEVELS Change in Sound Level Apparent Change in Loudness 3 dB Just perceptible 5 dB Noticeable 10 dB Twice (or half) as loud 3 The sound pressure level is defined as 20*log10 (P/Po) where P is the sound pressure and Po is the reference pressure of 20 micro-Pascals (20 Pa), which by definition corresponds to 0 dB. 4 Community noise studies and regulations use an A-weighting scale when measuring sound pressure levels as this approximates the response of the human ear to sounds we experience in everyday life, namely those in the range of 0 to 85 A-weighted decibels (dBA). There is also a C-weighting scale that was designed only for human exposure to very loud sounds, namely those over 85 decibels.4 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 for very loud sounds, such an inappropriate choice would artificially inflate low-frequency sound. Typical sound levels associated with various activities and environments are presented in Figure 1. Here are examples of sound levels we all encounter. A quiet rural area at night without any traffic typically has an average sound level of 35 dBA, while 45 dBA represents a quiet suburban area. The freight train you hear in the distance may be 50 dBA, and crickets and tree frogs in the summer will easily sing a sound level of 55 dBA. Two people having a conversation in a normal tone of voice will hear each other speak at 65 dBA. Standing near a road, a car passing by can produce 75 dBA, and a truck passing by is louder at 80 dBA. Thus, sound levels above 45 dBA are common in rural areas. A farm tractor or combine will produce 85 dBA if you are 50 feet away. A gas-powered lawn mower you might push around your yard makes a sound of 95 dBA. The distance to a major road often determines the acoustic environment in a rural area such as Enfield, as roadway traffic is the predominant sound source. Sound levels 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 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 energy-average sound level and it represents all of the sound we hear. EPA has determined that the Leq average sound level correlates best with how people perceive and react to sound.5 4 Bolt, Beranek, and Newman, Inc., Handbook of Noise Ratings, NASA-CR-2376, April 1974, page 21. 5 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-550/9-74-004. 5 To establish the quietest-interval sound level in an area, the L90 metric, which is the sound level exceeded 90 percent of the time, is often used. The L90 represents the quietest 10 percent interval of any time period as 90% of the existing sound energy has been eliminated. Sound 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, and typically the frequency analysis examines nine octave bands from 32 Hz to 8,000 Hz. A source creates a pure tone, as defined by American National Standards Institute (ANSI) Standard S12.9, if acoustic energy is concentrated in a narrow frequency range and a 1/3-octave band has a sound level 5 to 15 dB greater than both adjacent bands (5 dB for high frequencies, 8 dB for middle frequencies, and 15 dB for low frequencies). FIGURE 1. Common Outdoor Sound Levels 7 3.0 NOISE REGULATIONS AND CRITERIA 3.1 Local Wind Energy Facilities Law The Wind Energy Facilities Local Law sets a sound limit of 60 dBA6 at the nearest non-participating residence. 3.2 State Noise Guidelines and Ambient Sound Levels The New York State Department of Environmental Conservation (NYS DEC) uses a Noise Guideline document7 to assess noise impacts under the SEQRA 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.”8 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 it 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.”9 Ambient sound level measurements were collected by HMMH between April 14 and 19, 2011 at three long-term, and four short-term, sound monitoring locations in the Enfield project area.10 The 10- minute Leq sound levels were analyzed to identify those time periods: (1) for which hub-height wind speeds were at least 10 m/s, approaching the design speed at which the turbines will produce maximum sound power, and (2) for which there was no measurable precipitation, a requirement of ANSI Standard S12.18-1994. These criteria were only met for the three long-term monitoring stations LT1 through LT3. The overall Leq sound level across the three sites and all hours was 39.8 dBA.11 This 6 Actually the Local Law states “60 dBA above ambient sound levels” which will be interpreted to mean 60 dBA. 7 NYS DEC, “Assessing and Mitigating Noise Impacts,” Program Policy Guideline DEP-00-1, February 2001. DEC staff note that this document is presently being revised. 8 Ibid, pp. 12-13. 9Ibid, p. 14. 10 HMMH, “Noise Study for Black Oak Wind Farm,” March 9, 2012. 11 Ibid, Appendix B. 8 measured ambient level is 5 dBA less than the suggested 45 dBA ambient level in the NYS DEC Noise Guideline for “a seemingly serene setting such as rural farm land,”12 a description that fits Enfield. Following the NYS DEC Guideline and adding 6 dBA, the project goal for non-participating residences is therefore a sound level no higher than 45.8 dBA, rounded down to a sound level no higher than 45 dBA. This is not an enforceable regulatory limit, and the NYS DEC Guideline is used solely to judge whether sound levels are at a level to require further analysis or mitigation. Regarding seasonal variations, ambient sound levels are generally 5 dBA higher in the leaf-on summer season due to wind blowing tree foliage and warm-weather insect noise. Thus, ambient sound levels in the project area can be characterized as 40 dBA in the leaf-off season, and 45 dBA in the leaf-on season. The NYS DEC Guideline also notes the EPA residential goal of 55 dBA for the day-night sound level (Ldn).13 An L dn of 55 dBA is equivalent to Leq of 48.6 dBA for a continuously operating sound source such as a wind farm. For this project, the NYS DEC Leq and Ldn guidelines were applied at the nearest non-participating residences in the project area. Of these, the NYS DEC guideline of 45 dBA is lower and was used for evaluating predicted wind turbine sound levels. To assess the potential for low frequency vibrations at residences, the protective criteria from ANSI Standard S12.9/Part 4, Annex D were employed in this study. Those recommended limits at the external wall of a non-participating residence are 65 dB in the 31.5 and 63 Hz low-frequency octave bands. The ANSI Standard recommends these limits to prevent annoyance and noticeable vibrations in building elements. The lowest frequency band for which turbine sound power levels are published is the 31.5 Hz band. 12 NYS DEC, page 20. 13 US EPA, “Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety,” EPA-550/9-74-004, 1974. 9 4.0 CALCULATED FUTURE SOUND LEVELS 4.1 Methodology Future maximum sound levels from 7 wind turbines, plus a 55-MVA power transformer at the proposed substation, at occupied residences and lands within the Black Oak Wind Farm project area 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 961314. Atmospheric absorption, the process by which sound energy is absorbed by the air, was calculated using ANSI S1.26-1995.15 Absorption of sound by the atmosphere assumed standard day conditions and is significant at large distances for higher frequencies. Digital terrain heights were incorporated into the acoustic model. Decibel contour maps assume the above-listed worst case conditions can occur for any wind direction and present a composite sound level map that assumes all receiver locations are downwind of all wind turbines. The acoustic modeling results are conservative due to the following assumptions: 1. All wind turbines were assumed to be operating simultaneously. 2. All wind turbine sound power levels correspond to the IEC 61400-11 maximum sound power level plus an uncertainty factor. 3. The acoustic model assumed the most favorable conditions for sound propagation, corresponding to a ground-based temperature inversion, such as might occur on a calm, clear night, or during a downwind condition with a wind speed of 1 to 5 m/s (2 to 11 mph). 4. No attenuation from trees or other vegetation was assumed. 5. Winter frozen ground conditions were assumed for minimal ground absorption. (G=0.5 in the model, representing a mixed ground surface that is midway between completely absorptive and reflective. Most of the year the ground surface in the project area is highly absorptive). 6. Excess attenuation from wind shadow effects and daytime air turbulence were ignored. 14 International Standard, ISO 9613-2, Acoustics – Attenuation of Sound During Propagation Outdoors, -- Part 2 General Method of Calculation. 15 American National Standards Institute, ANSI S1.26-1995, American National Standard Method for the Calculation of the Absorption of Sound by the Atmosphere, 1995. 10 Sound power level is on a decibel scale16, leading to possible confusion since sound power (energy density) and sound pressure (what we hear) are not the same. Cadna/A 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. The maximum sound power level for a GE 1.7-100 turbine for this project has been specified by the manufacturer as 104.0 dBA (IEC 61400-11 test value), to which a K-factor of 2.0 dBA was added to represent measurement and turbine production uncertainty, yielding a total sound power level of 106.0 dBA for normal operations. The maximum sound power levels in the 31.5 Hz and 63 Hz bands for the GE 1.7-100 turbine are 113.5 dB and 110.0 dB, respectively. The K-factor of 2.0 dB was added to all octave band values. 4.2 Sound Level Contour Map Figure 2 presents a color-coded decibel sound pressure level contours (5 feet above grade) for Black Oak Wind Farm operation at the design wind speed (maximum sound power level) with 5-dBA contour lines. Maximum sound levels fall below the Local Law limit of 60 dBA within a short distance (less than 200 feet) from the base of each turbine tower, and for that reason 60-dBA contour lines are not shown. Predicted maximum sound levels at all Non-Participating residences are well below 60 dBA and thus the project, designed with the GE 1.7-100 turbines, will fully comply with the sound limit in the Enfield Wind Energy Facilities Law.     4.3 Maximum Sound Levels at Occupied Structures Maximum sound levels at all occupied structures are listed in Appendix A for the Black Oak Wind Farm. Note that the results have been sorted from highest to lowest sound impacts. The table provides a unique identifier for the residence, a general description of its location, and the predicted maximum broadband sound level (dBA) as well as the maximum low frequency sound levels (dB) in the 31.5 Hz and 63 Hz bands. In Table A-1, the maximum sound level at an occupied residence is 45.9 dBA at Receptor 14 on Black Oak Road. The three receptors above the black line shown in Appendix A should be considered as Participants of the Project to keep project impacts below 45 dBA at Non-Participating residences. 16 The sound power level is defined as 10*log10 (W/Wo), where W is the sound power of the source in Watts and Wo is the reference power of 10-12 Watts. 13.-2-6.2 12.-1-4 12.-2-9 13.-1-4.121 18.-1-6 13.-2-5.2 18.-1-10 12.-1-7 18.-1-9 12.-2-10 13.-2-1.2 1.-1-25 13.-2-2.12 13.-1-4.11 1.-1-4 18.-2-2.22 12.-1-5 17.-1-3.1 17.-1-1.22 14.-1-13.2 18.-1-3.22 12.-2-8 1.-1-2 13.-2-4 14.-1-2.2 18.-3-6 18.-1-1 14.-1-12 17.-1-3.1 18.-3-4.2 13.-1-2.1 18.-3-5.22 14.-1-1.32 1.-1-1 17.-4-1.2 2.-1-1 13.-1-3.22 18.-1-4.2 13.-2-3.2 18.-1-5 18.-2-4.3 2.-1-28 14.-1-1.2 1.-1-3 1.-1-6 18.-3-8.2 18.-2-1.21 18.-1-3.21 1.-1-10 12.-2-4.2 1.-1-8.2 17.-1-1.22 12.-1-8 18.-1-2 2.-1-2.22 18.-2-10 18.-1-7 18.-3-5.13 12.-2-6 18.-3-4.2 13.-1-4.121 2.-1-2.21 12.-2-4.2 18.-2-13.2 1.-1-5 13.-1-4.122 18.-2-1.27 13.-2-3.3 18.-1-3.1 12.-2-5 13.-1-4.4 2.-1-27 1.-1-1 13.-1-4.22 12.-2-11.3 14.-1-1.2 11.-1-31.211.-1-31.3 18.-2-8.2 13.-1-6.2513.-1-6.16 13.-2-1.1 13.-2-7.8 18.-3-7 13.-2-3.1 11.-1-2.1 18.-2-14 1.-1-8.1 13.-1-6.13 13.-1-2.21 18.-1-3.31 13.-1-2.22 13.-1-6.2 18.-3-2.5 13.-2-1.31 13.-1-6.27 18.-3-2.3 13.-2-7.2 18.-3-1.2 13.-2-7.7 18.-1-3.4 18.-3-2.4 11.-1-32.42 18.-3-2.2 18.-2-7.1 13.-2-7.5 13.-1-6.28 17.-1-9 18.-2-4.1 12.-2-10 13.-1-6.4 18.-2-4.3 18.-2-1.25 13.-1-3.21 1.-1-8.4 18.-1-3.8 13.-1-6.26 11.-1-31.5 13.-1-6.5 13.-1-6.9 18.-3-8.32 18.-2-2.1 18.-2-1.24 17.-4-1.1 1.-1-8.3 13.-1-6.18 13.-1-6.19 13.-1-6.20 13.-1-6.21 13.-1-6.22 13.-1-6.23 18.-1-3.32 18.-2-1.23 18.-2-13.12 13.-1-6.11 18.-3-2.11 18.-3-2.12 18.-1-8 13.-1-6.10 13.-1-6.12 18.-2-1.32 13.-2-7.4 18.-3-4.1 13.-1-3.1 18.-2-1.7 13.-1-6.6 13.-2-7.1 13.-2-5.42 13.-2-6.3 17.-1-3.1 18.-2-1.4 18.-3-2.7 13.-1-4.3 17.-1-8 1.-1-8.5 18.-3-5.14 13.-2-7.6 17.-1-1.21 18.-1-3.6 17.-1-3.2 18.-1-4.1 13.-1-5 14.-1-13.1 11.-1-32.43 18.-2-9.2 17.-1-1.3 18.-1-3.5 18.-1-3.23 18.-3-3.1 17.-1-1.1 13.-2-2.2 13.-2-5.3 14.-1-2.4 18.-3-8.7 18.-1-3.2418.-2-1.62 18.-2-1.13 13.-2-2.11 13.-2-5.41 13.-1-3.23 18.-2-1.34 18.-2-10 12.-2-11.2 11.-1-32.44 18.-2-11 12.-1-2.32 12.-1-2.31 11.-1-32.3 18.-3-1.1 18.-3-2.6 18.-3-2.8 18.-2-13.11 14.-1-1.33 11.-1-34 18.-3-8.4 17.-4-2.2 18.-3-8.1 18.-2-1.5 18.-3-8.31 11.-1-33 13.-2-6.1 13.-2-7.3 14.-1-1.1 11.-1-1.1 13.-2-5.1 14.-4-6 18.-2-1.14 14.-1-1.34 T1 T2 T3 T4 T5 T6 T7 R9 R8 R7 R5 R4 R3 R2 R86 R83 R79 R78R74 R72 R62R61R60R59 R54 R53R52R51 R49 R46 R45 R41 R38 R37 R35 R24 R21 R18 R16 R12 Copyright:© 2013 Esri, DeLorme, NAVTEQ, TomTom, Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community Figure 2 Maximum Sound Levels (dBA) for the Black Oak Wind Energy Project Enfield, NY GE 1.7-100 MW Turbines 0 1,000 2,000 3,000 4,000500 Feet ± Legend Sound Level 35 dBA 40 dBA 45 dBA 50 dBA 55 dBA Turbines "J Occupied Structures 12 4.4 Low Frequency Sound, Vibration and Tonality The frequency spectra for the GE 1.7-100 turbines were analyzed for tonality using ANSI Standard S12.9/Part 3, Appendix C and no pure tones were found. While a spectrum was not available for the transformer, the maximum sound level from the substation transformer (alone) at a residence is only 34.4 dBA at Receptor 24 on Black Oak Road. Whereas this level is less than the ambient level of 39.8 dBA for the project area, no pure tone impacts are expected at any Non-Participating occupied residences. Low-frequency sound refers to sounds below 200 Hz in frequency, which is close to the tone of Middle-C on a piano. The potential for low frequency noise impacts was first assessed as follows. Using the turbine sound power level spectra for full-power operation, the broadband sound power levels for both A-weighting and C-weighting scales17 were calculated and the difference was then compared to a 20-decibel (dB) threshold recommended in International Standard IEC 61400-11 as a check on whether a wind turbine may produce low-frequency noise that could create annoyance.18 The (dBC-dBA) difference for the GE 1.7-100 is 10.7 dB. This result is well below the 20-dB IEC threshold. Thus, the frequency spectra this turbine model selected for Black Oak Wind Farm suggest the turbines will not produce low frequency noise that could cause annoyance. The maximum low frequency sound levels (Appendix A) in the 31.5 and 63 Hz octave bands at an occupied building are 60 and 57 dB, respectively. These levels are well below 65 dB in each band, the protective criteria from ANSI Standard S12.9/Part 4, Annex D. The results suggest low frequency sound from Black Oak Wind Farm will not cause annoyance or noticeable vibrations in building elements at any nearby receptors. The hearing threshold in the 31.5 Hz low-frequency octave band is 70 dB19. The predicted maximum 31.5 Hz sound level from the project is lower at 60 dB. Thus, low frequency sound below 40 Hz will not be audible from Black Oak Wind Farm. 17 The A-weighting scale approximates the hearing response of the human ear for levels typically encountered in daily life and is most appropriate for community wind studies. The C-weighting scale was designed for very loud noises at or above 85 decibels and it applies a heavier weighting to low-frequency sound than the A-weighting scale. 18 International Standard IEC 61400-11, “Wind turbine generator systems – Part 11: Acoustic noise measurement techniques,” Annex A, p. 38. 19 International Standards Organization, ISO 226:2003, “Acoustics – Normal equal-loudness–level contours,” 2003. 13 Measurements of existing sound level spectra from the three long-term monitoring locations in the project area20 reveal naturally-occurring low-frequency sound levels in the range of 63 to 80 dB for the 31.5 Hz band, and naturally-occurring low-frequency sound levels in the range of 62 to 74 dB for the 63 Hz band. Whereas the maximum wind farm low frequency sound levels at any occupied residence are lower, it can be concluded that Black Oak Wind Farm will not expose people, wildlife, or livestock to low frequency sound levels higher than those already occurring in the natural environment of Enfield, and the wind farm’s sound therefore does not pose a risk to these individuals.     4.5 Infrasound and Health Effects Infrasound is low-frequency sound at frequencies below 20 Hz, a sound wave oscillating only 20 cycles per second. For comparison, the lowest key on a piano produces a tone of 28 Hz, and human speech is in the range of 500 to 2,000 Hz. The hearing threshold for infrasound at 16 Hz is 90 decibels (dB).21 We are enveloped in naturally occurring infrasound, which is inaudible. Infrasound is always present in the outdoor environment due to sounds generated by air turbulence, motor vehicle traffic and distant aircraft. Infrasound we encounter from these common sources can be at a level similar to that from a wind turbine. A noted British acoustic scientist, Dr. Geoff Leventhall, has studied infrasound extensively and he concludes “there is insignificant infrasound from wind turbines” and “there is no reliable evidence that infrasound at levels below the hearing threshold has an adverse effect on the body.”22 The EPA has concluded that infrasound below the hearing threshold produces no physiological or psychological effects, and the small amount of infrasound from a turbine is less than that in the natural environment.23 20 HMMH, Appendix B. 21 International Standards Organization, ISO 226:2003. 22 Leventhall, Geoff, “Infrasound from Wind Turbines – fact, Fiction or Deception,” Canadian Acoustics, Vol. 34, No. 2, pages 29-36, 2006. 23 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-550/9-74-004, page G-11. APPENDIX A ACOUSTIC MODELING RESULTS FOR OCCUPIED STRUCUTURES GE 1.7-100 TURBINES A-1 Cadna A Modeling Results GE 1.7-100 Turbines ID Name Total 31.5 Hz 63 Hz Coordinates Level Band Level Band Level X Y Z (dBA) (dB) (dB) (m) (m) (m) R14 Black Oak Rd. 3rd from north 45.9 60 57 362688 4696325 531 R8 Black Oak Rd. 10th from top 45.8 60 57 362872 4695788 559 R16 Black Oak Rd. 4th from north 45.2 60 56 362694 4696277 534 R45 Connecticut Hill Rd. 6th From West 44.7 59 56 363323 4696111 515 R13 Black Oak Rd. 2nd from north 44.7 59 56 362782 4696381 527 R39 Connecticut Hill 2nd from West 44.5 59 56 363005 4696130 540 R40 Connecticut Hill 4th from West 44.5 58 55 363083 4696134 535 R42 Connecticut Hill Rd 5th from West 44.4 59 55 363198 4696133 523 R50 Connecticut Hill seventh from left 44.3 59 56 363195 4696208 528 R20 Black Oak Rd. 7th from north 44.1 59 55 362818 4695978 554 R21 Black Oak Rd. 7th from north 44.1 59 55 362818 4695978 554 R7 Black Oak Rd furthest north 44 59 55 362757 4696761 506 R47 Connecticut Hill West 3rd from West 44 59 55 363028 4696212 541 R35 Chapman Road 2nd from Top 44 59 55 362944 4696503 514 R18 Black Oak Rd. 5th from north 43.8 59 55 362784 4696195 544 R46 Connecticut Hill West 43.7 59 55 362923 4696212 544 R19 Black Oak Rd. 6th from top 43.6 58 55 362714 4696122 544 R68 Griffin Rd. 10th East 43.4 58 54 363383 4695171 554 R44 Connecticut Hill Rd. 4th From east 43.5 58 54 363549 4696213 503 R22 Black Oak Rd. 8th from top 43.2 58 55 362706 4695830 561 R10 Black Oak Rd. 12th from top 43 58 54 362783 4695538 568 R5 Black Oak 9th from north 43 58 54 362695 4695780 563 R9 Black Oak Rd. 11th from north 42.8 58 54 362745 4695550 567 R43 Connecticut Hill Rd. 3rd From East 42.8 57 54 363603 4696204 494 R1 Black Oak 13th from north 42.5 58 54 362806 4695414 569 R11 Black Oak Rd. 13th from north 42.5 58 54 362806 4695414 569 R78 Griffin Rd. 8A 42.5 57 54 363300 4695148 559 R48 Connecticut Hill and Rumsey Rd 42.4 58 54 363743 4696228 502 R2 Black Oak 14th from top 42 57 54 362810 4695230 578 R12 Black Oak Rd. 14th from top 42 57 54 362810 4695230 578 R6 Black Oak Rd at Griffin 41.6 56 53 362817 4695125 584 R70 Griffin Rd. 13th East 41.5 56 52 363544 4695087 540 R76 Griffin Rd. 6th East 41.4 57 53 363105 4695133 571 R62 County Road 183 furthest east 41.2 57 53 362518 4696982 498 R24 Black Oak South of Griffin 41.5 56 53 362820 4694946 588 R74 Griffin Rd. 4th East 41.2 57 53 363016 4695135 576 R73 Griffin Rd. 3rd East 41.2 57 53 362969 4695135 578 R69 Griffin Rd. 12th East 41.2 56 52 363513 4695064 545 R80 Griffin Rd. near Black Oak Rd. 40.8 56 53 362917 4695067 581 R81 Griffin Road 4A 40.5 56 53 363038 4695053 578 R49 Connecticut Hill and Rumsey Rd. 40.5 56 52 363894 4696088 507 R77 Griffin Rd. 7th East 40.4 56 52 363223 4695056 565 R38 Connecticut Hill 2nd Furthest East 40.3 56 52 363956 4695846 507 R72 Griffin Rd. 14th East 40.3 54 51 363717 4695107 521 R3 Black Oak 2A south of Griffin 40.2 55 52 362878 4694906 588 R75 Griffin Rd. 5th East 40 56 52 363097 4694996 577 R61 County Road 183 7th from west 39.9 55 51 362185 4696924 485 R15 Black Oak Rd. 3rd from south 40 55 52 362819 4694773 601 R17 Black Oak Rd. 4th from south 40 55 52 362819 4694773 601 Cadna A Modeling Results GE 1.7-100 Turbines ID Name Total 31.5 Hz 63 Hz Coordinates Level Band Level Band Level X Y Z (dBA) (dB) (dB) (m) (m) (m) R71 Griffin Rd. 13th East 39.7 55 51 363704 4695045 518 R79 Griffin Rd. at Right Corner 39.5 54 50 363987 4695298 506 R41 Connecticut Hill Furthest East 39.2 54 51 364021 4695772 501 R53 County Rd 183 6th from west 38.4 54 51 362014 4696919 475 R4 Black Oak 2nd from south 38 52 49 362824 4694702 603 R52 County Rd 183 4th from west 36.9 53 50 361790 4696865 462 R60 County Road 183 5th from west 36.1 52 49 361809 4696956 464 R23 Black Oak Rd. Furthest south 36.1 51 48 362822 4694581 599 R29 Cayutaville Rd. 2nd from Black Oak 35.7 51 47 362926 4694605 605 R37 Chapman Road 6A from left 34.5 52 48 361543 4696931 445 R86 Tower Rd furthest south 34.7 51 47 362739 4694363 593 R31 Cayutaville Rd. furthest west 34.4 50 46 363064 4694494 602 R83 State Park furthest north 32.9 50 47 362593 4694089 622 R51 County Rd 183 3rd from west 32.5 50 46 361327 4696919 441 R82 State Park 2nd from north 32.3 50 46 362612 4694031 634 R84 State Park furthest south 32.3 50 46 362612 4694031 634 R59 County Road 183 2nd west 31.9 49 46 361240 4696910 450 R54 County Rd 183 furthest west 30.8 48 44 361150 4696909 460 R56 County Rd 6 4th North 30.1 47 44 360612 4696130 437 R25 Buck Hill Rd 29.9 47 44 361157 4697071 461 R26 Buck Hill Road North 29.9 47 44 361157 4697071 461 R27 Buck Hill furthest west 29.2 47 43 361147 4697189 460 R34 Chapman Road #3 29.2 47 43 360963 4697000 473 R55 County Rd 6 3rd North 29.2 46 42 360606 4695603 426 R63 County Road 6 2nd North 29.1 46 42 360609 4695477 427 R33 Chapman Road #2 28.3 46 43 360638 4696722 466 R65 County Road 6 Sxith from South 28.1 45 42 360492 4695513 423y R58 County Rd. 6 Third from South 28.1 45 42 360513 4695383 423 R32 Chapman Rd. 28.1 45 41 360565 4696556 466 R66 County Road Second from South 27.5 45 41 360496 4695222 424 R67 County Route 6 5th north 27 44 41 360453 4696202 450 R30 Cayutaville Rd. East 26.8 41 38 363331 4694141 587 R57 County Rd. 6 6th North 26.5 44 40 360385 4696192 444 R64 County Road 6 South 26.2 44 40 360466 4694882 427 R36 Chapman Road 4th from bottom 26 38 35 360570 4696711 461 R28 Cayutaville Rd west 24.6 43 39 360416 4694541 434 R87 Tower Rd. 2nd to south 22.4 37 33 362566 4693683 637 R88 Tower Rd. south 22 36 33 362715 4693667 629 R85 States Rd < 20 < 45 < 40 360410 4694375 436