Framework for windnoise studies

Abstract

Research in wind noise reduction in outdoor measurement microphones has been limited largely to comparisons between bare and screened microphones. Morgan and Raspet [J. Acoust. Soc. Am. 92, 1180–1183 (1992)] used simultaneous wind velocity and noise measurements to show that the source of wind noise is incident wind fluctuations. In this paper, two methods for predicting the upper limits of wind noise pressure spectra from velocity spectra in the inertial range are developed. A lower limit on wind noise is estimated from two theories of the intrinsic turbulent pressure fluctuations. Empirical results for the self-noise windscreens in substantially non-turbulent flows are also presented. Measurements of the wind velocity spectra and wind noise spectra from a variety of windscreens are described and compared to the theoretical predictions. All of the wind noise data lies between the upper and lower limits. The theoretical framework allows windscreens to be evaluated in terms of the best and worst-case scenarios and establishes practical lower limits on wind noise reduction for varying wind conditions. [Work supported by the Collaborative Technology Alliance sponsored by the US Army Research Laboratory.]