Minimizing wind effects on active control systems for attenuating outdoor transformer noise

Turbulent pressure fluctuations resulting from wind blowing over a microphone can result in significant distortion of the acoustic signal output from the microphone. This distortion can have a significant detrimental impact on an active noise cancellation system used to reduce the noise radiated by an outdoor source such as an electrical power transformer. Even using a band pass digital filter in the active noise canceling electronics is ineffective because the large wind-induced signal effectively reduce the dynamic range of A/D converters. Here the characteristics of wind-induced noise and standard foam windscreens are analyzed and the effectiveness of a high pass filter together with a foam windscreen for reducing the effect of wind-induced signals are evaluated. Combination of a windscreen with a high pass filter of appropriate order is shown to increase the signal to noise ratio of the transformer sound by about 20 dB over that achieved with a windscreen only. (C) 2000 Institute of Noise Control Engineering.