The Importance of Screening Wind Gust Noise in Wind Turbine Compliance Testing

Short-term noise contamination from wind gusts is a significant problem for sound compliance testing at wind farms. Unattended monitoring cannot firmly identify gust noise and, except in two special cases, is not as accurate as attended measurements. Attended testing using ANSI S12.9/Part 3 requires detailed screening procedures for both short and long term noise, and those ANSI procedures are not always correctly applied by consultants, resulting in over-statement of wind turbine sound. Reliance on the ANSI S12.18 2-meter wind speed threshold of 5-m/s is necessary, but not sufficient, in screening wind gust noise. Sound measurement graphs from four wind projects in the Midwest, Mid-Atlantic, Upstate New York and New England regions are presented and discussed to illustrate the errors caused by improper screening. Failure to screen wind gust noise causes 1-minute Leq error of over 10 dBA and 10-minute Leq errors of 2 to 5 dBA, resulting in false conclusions of non-compliance. The Tech Environmental method of real-time screening for wind gust noise, using both audibility and LAF meter response, is described as part of a complete application of the ANSI S12.9/Part 3 test procedures, with recommendations for 2-meter anemometer placement.