Industrial Wind Farm

NoiseThor Vandehei, PhD

(Physics, UCSD)

FLPA

Finger Lakes Preservation Association

Three important characteristics of noise to consider (in order of increasing importance for wind farms):

1. Noise Level:Sound Pressure Level - SPL

2. Frequency Content (i.e., Noise Spectra): Low-frequency (20-200 Hz) and Infrasound (< 20 Hz)

3. Temporal Character:Impulsive character of noise (i.e., amplitude modulation of broadband noise)

*Sound levels are measuredon a logarithmic scale in unitscalled decibels (dB).

*Each addition of +10 dB is a 10 fold increase in sound “energy” and represents roughly a twice “perceived” increase in loudness by the human ear.

*Often frequency weighted by an “A-filter” to mimic human hearing and thus is not sensitive to low frequency or infrasound noise.

*An absolute scale of sound pressure levels (SPL) is useful, but new noise sources must be compared with pre-existing ambient noise levels (DEC guidelines)

Source: NYS DEC Assessing and Mitigating Noise Impacts (2001)

1.Noise Level

1.Noise Level (continued)

• Wind farm developers favor setting noise level standards of 50 dBA or higher (to minimize setbacks to residences), often claiming that 50 dBA is considered “Quiet” by the NYS DEC (with no regard for pre-existing ambient noise levels, which are often in the low to mid 20 dBA range at night in rural settings.)

• The NYS DEC Assessing and Mitigating Noise Impacts (2001) policy document specifies keeping a new noise sources below +6 dBA above pre-existing ambient noise levels to avoid complaints.

• Increases in sound pressure level of +20 dBA is considered “Very Objectionable to Intolerable” by the NYS DEC.

2. Frequency Content

Source: Van den Berg, G.P. (2004) “Do wind turbines produce significant low frequency sound levels?”, 11th International Meeting on Low Frequency Noiseand Vibration and its Control, Maastricht, The Netherlands, 30 August to 1 September 2004

*Measured 2500 feet from nearest WTG.

*52 dB @ 10 Hz issufficient to rattlewindows and other structural elements.

*All modern, up-winddesigned WTG generate significant low-frequency and infrasound noise levels

3. Temporal Character

Source: Kamperman, G.W. & James, R.R. “The How To Guide to Siting Wind Turbines To Prevent Health Risks From Sound”, Extended version of paper presented at NOISE‐CON 2008 (October 28, 2008)

*Measured3000 feet fromnearest WTG,inside a bedroom.

*AmplitudeModulation is +5 to+6 dBA with 1 cycle per second.

*Described as “distant pile driving”or “a dripping faucet”

*Not readily maskedby increases in ambient noise levels

Source: Pederson, K. and Waye, K. (2004) “Perception and annoyance due to wind turbine noise – a dose – response relationship”, J. Acoust. Soc. Am. 116(6), December 2004

Conclusion: Wind turbine noise, due to its persistent nature (especially at night), low frequency content, and impulsive character is more highly annoying then equivalent noise levels experienced due to aircraft, road traffic and railways – yet EPA guidelinesdesigned for the latter three noise sources are being used to justify siting wind farmsas close as 1000 feet from homes (with resultant noise levels of 50 dBA and higher).