Low-frequency wind noise correlation in microphone arrays.

A three-axis orthogonal microphone array with ten sensors in each arm has been used to study wind noise in the frequency range from 0.05 to 50 Hz. Simultaneous measurements were made of the three components of the varying wind velocity. Measurements have been made for wind speeds from 4 to 7 m/s at three different sites. The frequency-dependent correlation of the wind noise over a range of wind velocities and atmospheric and environmental conditions in the downwind direction varies as exp(-3.2X)cos(27piX). For the crosswind and vertical directions, the correlation decays approximately as exp(-7Y), where X is the separation in wavelengths in the downwind direction and Y is this separation in the crosswind or vertical direction. Over a limited range of wave numbers, the power density spectra of the varying wind velocity varied as the wave number to the -(5/3) power and the pressure spectra as the -(7/3) power.