Bidirectional Microphone Array with Adaptation Controlled by Voice Activity Detector Based on Multiple Beamformers

Ambient noise suppression in a reverberant room is usually performed by the microphone array. The adaptive beamforming, whose typical representative is minimum variance distortionless (MVDR) beamformer, is an effective method for noise suppression. However, MVDR beamformer gives poor results in the real room because of its sensitivity to the steering error and the multipath wave propagation. In this paper we propose a noise suppression method based on assumption that the positions of the speakers in the reverberant room are roughly known. Noise reduction is realized by two MVDR beamformers directed toward each of the speakers. Adaptation of the MVDR beamformers are controlled by a speaker activity detector which decision is based on power transfer model of the multiple superdirective beamformers in combined diffuse and coherent noise field. The proposed voice activity detector also provides residual noise reduction. The proposed method and its robustness to steering error were tested on the model of simulated room as well as in real room environment. The improvement of the restored speech signal was evaluated by Signal to Noise Ratio Enhancement (SNRE) and by Perceptual evaluation of speech quality (PESQ) measure.