These guidelines were developed by sound experts George W. Kamperman and Richard R. James and are included in a paper they will be presenting at the NOISE-CON 2008 conference in Dearborn, Michigan (USA) July 28-31. The paper is not available for publication, but I think all of you will appreciate the title: "Simple guidelines for siting wind turbines to prevent health risks" .
Lisa Linowes
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1. Audible Sound Limit
a. No Wind Turbine or group of turbines shall be located so as to cause an exceedance of the preconstruction/operation background sound levels by more than 5 dBA. The background sound levels shall be the L90A sound descriptor measured during a pre-construction noise study during the quietest time of evening or night. All data recording shall be a series of contiguous ten (10) minute measurements. L90A results are valid when L10A results are no more than 15 dBA above L90A for the same time period. Noise sensitive sites are to be selected based on wind development's predicted worst-case sound emissions (in LeqA and LeqC) which are to be provided by developer.
b. Test sites are to be located along the property line(s) of the receiving non-participating property(s).
c. A 5 dB penalty is applied for tones or when the sound emissions fluctuate in amplitude or frequency over
time in reasonable synchronicity with the blade revolution.
2. Low Frequency Sound Limit
a. The LeqC sound levels from the wind turbine at the receiving property shall not to exceed the lower of either:
1) LeqC-L90A greater than 20 dB outside any occupied structure, or
2) A maximum not-to-exceed sound level of 50 dBC.
These limits shall be assessed using the same nighttime and wind/weather conditions required in 1.a.
Turbine operating sound immissions (LeqA and LeqC) shall represent worst case sound immissions for stable nighttime conditions with low winds at ground level and winds sufficient for full operating capacity at the hub.
3. General Clause
a. Not to exceed 35 dBA within 30 m. (approx. 100 feet) of any occupied structure.
4. Requirements
a. All instruments must meet ANSI or IEC Precision sound level meter performance specifications.
b. Procedures must meet ANSI S12.9 and other applicable ANSI standards.
c. Measurements must be made when ground level winds are 2m/s (4.5 mph) or less. Wind shear in the evening and night often result in low ground level wind speed and nominal operating wind speeds at wind turbine hub heights.
d. IEC 61400 procedures are not suitable for enforcement of these requirements. ANSI standards shall be followed for testing procedures.
http___www.windaction.pdf
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