Measurement and rating of amplitude modulation in low frequency wind turbine noise

Amplitude modulation in wind turbine noise refers to the distinct periodic variation in amplitude which can be perceived more than a constant level. A method for rating amplitude modulation in wind turbine noise, intended for noise in 1/3 octave bands between 50 and 800 Hz, is described in Final Report A Method for Rating Amplitude Modulation in Wind Turbine Noise 9 Aug 2016 Version 1, Institute of Acoustics IOA Noise Working Group (Wind Turbine Noise) Amplitude Modulation Working Group. This paper examines the measurement and rating of amplitude modulation in wind turbine noise below 50 Hz, below the intended range of the method described in the Institute of Acoustics report. A tonal analysis as per ETSU-R-97 is also made, and the results compared.