Measurement and quantification of low frequency noise emissions from utility-scale wind turbines

In wind turbine project permit hearings and other proceedings, concerns are often raised regarding low frequency noise (LFN). As the size of utility-scale wind turbines continues to grow, the concern over LFN may only intensify. This paper describes the measurement and quantification of low frequency noise emissions from utility-scale wind turbines, specifically in the 16, 31.5, and 63 Hertz octave bands. Accurate measurement of wind turbine noise emissions, particularly in the 16 Hertz octave band, is challenging due to interference from wind-induced noise. Topics covered include choice of windscreen, the effectiveness of shutdown tests, data filtering techniques, and the comparison of measured levels at multiple wind turbine sites to levels predicted using manufacturer's data and the ISO 9613-2:1996 method.