IEEE Approved Draft Standard of Wind Turbine Aero Acoustic Noise Measurement Techniques

The wind turbine in a wind farm can produce Amplitude Modulation Noise (AMN) is known to be caused by rotating airfoil self-noise particularly trailing edge scattering noise and Doppler effect due to blade motion relative to observer, it is also recognized as Swish sound. Envelop of the acoustic wave appeared to be blade passing frequency; therefore it gives people impression that it is Low Frequency with blade passing frequency noise. Meanwhile, the sound pressure pulsation due to blade aerodynamic loading fluctuation and blade tower interaction characterized as Low Frequency Noise (LFN) including infrasound were observed from indoor measurement near wind turbine in operation. The AMN and LFN are both identified as wind turbine aero acoustic noise that have been complained to be the most annoying to residents near wind farm, such as sleep disturbance, nausea, giddiness and etc. The issue becomes more concerned to public as more wind farm projects built with modern powerful wind turbine deploying larger and longer blade. However, the current IEC 61400-11 noise measurement standard did not address this issue, especially in far field indoor condition. To address this issue, IEEE has started a standard development project P2400 in Oct.2013. This standard establishes standard measurement techniques and methods of analysis to quantify wind turbine and wind farm aero acoustic noise. It can be used to understand wind turbine aero acoustic noise so called low frequency/infrasound and amplitude modulation noise and potential impacts on surrounding communities. This document provides the standard measurement techniques for wind turbine aero acoustic noise including instrumentation selection, measurement setup near field, far-field outdoor and indoor, post-data processing and noise source data analysis. IEC 61400-11 has provided overall wind turbine noise measurement standard, while this document focuses more aero acoustic noise of wind turbine and the difference from IEC 61400-11 to avoid the overlap. It is advised that use of this document also with familiarity of ANSI S1.1-1994 (R2004) Acoustical Terminology.