IN REVERBERANT ROOMS
R. Zelinski, Deutsche Bundespost · 1988
Speech comunication is often disturbed by acoustic room noise in the environment of the speaker. This paper presents a self-adapting noise reduction system which is based on a 4-microphone array combined with an adaptive post-filtering scheme. Noise reduction is achieved by utilizing the directivity gain of the array and by reducing the residual noise through post-filtering of the received microphone signals. The post-filtering scheme depds on a Wiener filter estimating the desired speech signal and is computed from shortterm measurements of the autocorrelation and cross-correlation functions of the microphone signals. The performance of the filtering scheme is increased substantially by additional post-processing of the cross-correlation measurements. The noise reduction system has been tested experimentally in a typical office room. The system produces an enhanced speech signal with barely noticeable residual noise if the input SNR is greater than 0 dB. The received noise power - measured in the absence of the speech signal - can be reduced by 28 dB.