Microphone wind speed limits during wind farm noise measurments

Guidelines and Standards which set environmental noise criteria often include clauses which prescribe a limit as to the allowable wind speed during noise measurements. It is common practice for this limit to be 5 m/s at the microphone, although 3 or 10 m/s are sometimes also adopted. The purpose of this limit for general environmental noise measurements may be to limit wind induced background noise, adverse propagation affects, wind induced noise on the microphone, or a combination of these. In the case of wind farm background noise assessments, the purpose of the measurements is to quantify the increase of wind induced background noise and a wind speed limit of 5 m/s at the microphone is typically adopted, with the sole aim of ensuring that wind induced microphone noise does not adversely affect the measurements by way of artificially increasing background noise. This paper examines the rationale for limiting wind speeds at the microphone to 5 m/s, and shows through field measurements that this limit does not guard against adverse effects of wind induced microphone noise. An alternative approach for preventing adverse effects of wind induced microphone noise is proposed.