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Sound propagation studies for a large horizontal axis wind turbineSystematic noise measurements in three directions with respect to the wind vector, over a range of distances to 1050 m, over a range of frequencies from 8 Hz to 2000 Hz, and for a stable wind turbine noise source (WTS-4) in windy conditions (V = 9.4 to 13.0 m/s) are presented. At frequencies above 63 Hz in the downwind and crosswind directions the sound pressure levels decay with distance according to predictions based on atmospheric absorption and spherical spreading, assuming no excess attenuation due to ground effects. In the upwind direction there is excess attenuation due to an acoustic shadow zone. The assumption of a distributed noise source leads to better noise estimates in the upwind direction. For very low frequencies 8 to 16 Hz no excess attenuation was observed in the upwind direction at distances up to 1050 m and a sound pressure level decay rate of approximately 3 dB per doubling of distance was observed in the downwind direction.
Document ID
19850016593
Document Type
Contractor Report (CR)
Authors
Shepherd, K. P. (Bionetics Corp. Hampton, VA, United States)
Hubbard, H. H. (College of William and Mary)
Date Acquired
September 5, 2013
Publication Date
March 1, 1985
Subject Category
ACOUSTICS
Report/Patent Number
NASA-CR-172564
NAS 1.26:172564
Funding Number(s)
CONTRACT_GRANT: NAS1-16978
PROJECT: RTOP 776-33-41
CONTRACT_GRANT: NAG1-166
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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NameType 19850016593.pdf STI