Measurement of wind turbine noise immission with a two-microphone technique

The measurement of wind turbine noise at an immission point at a large distance from the turbine is very often hindered by the high contribution of the ambient noise and of the wind-induced noise in the microphone. The use of a 2-microphone technique for the measurements could reduce the measured contribution of the ambient noise and the wind-induced microphone noise without the suppression of the measured wind turbine noise. The merits of this technique were assessed experimentally, both in the time domain and in the frequency domain. It is concluded that the measured contribution of the ambient noise and wind-induced microphone noise is indeed reduced significantly. However, also the measured contribution of the wind turbine noise is reduced to a certain extent. For this reason the application of the technique for wind turbine immission measurements is not recommended. 11 figs., 3 tabs., 2 refs