EURASIP Journal on Applied Signal Processing 
Volume 2003 (2003), Issue 11, Pages 1064-1073
doi:10.1155/S1110865703305050

An Integrated Real-Time Beamforming and Postfiltering System for Nonstationary Noise Environments

Israel Cohen,1 Sharon Gannot,2 and Baruch Berdugo3

 1Department of Electrical Engineering, Technion – Israel Institute of Technology, Haifa 32000, Israel
2School of Engineering, Bar-Ilan University, Ramat-Gan 52900, Israel
3Lamar Signal Processing, Ltd., Andrea Electronics Corp., P.O. Box 573, Yokneam Ilit, 20692, Israel
Received 1 September 2002; Revised 6 March 2003

Abstract

We present a novel approach for real-time multichannel speech enhancement in environments of nonstationary noise and time-varying acoustical transfer functions (ATFs). The proposed system integrates adaptive beamforming, ATF identification, soft signal detection, and multichannel postfiltering. The noise canceller branch of the beamformer and the ATF identification are adaptively updated online, based on hypothesis test results. The noise canceller is updated only during stationary noise frames, and the ATF identification is carried out only when desired source components have been detected. The hypothesis testing is based on the nonstationarity of the signals and the transient power ratio between the beamformer primary output and its reference noise signals. Following the beamforming and the hypothesis testing, estimates for the signal presence probability and for the noise power spectral density are derived. Subsequently, an optimal spectral gain function that minimizes the mean square error of the log-spectral amplitude (LSA) is applied. Experimental results demonstrate the usefulness of the proposed system in nonstationary noise environments.