Multiple-microphone time-varying filters for robust speech recognition

A multiple microphone time varying filter that is an extension of the dual-microphone speech enhancement technique of P. Aarabi et al. (see Proceedings of the IEEE Conference on Multimedia and Expo, Baltimore, Maryland, July 2003) is proposed and experimentally analyzed. The technique utilizes information regarding the locations of the speech source of interest and the microphones to compute a time varying filter that results in substantial noise reduction over other speech enhancement techniques such as delay-and-sum beamforming and superdirective beamforming. For example, digit recognition results in an environment with two speakers and a reverberation time of 0.1s show a recognition accuracy rate increase of 25.2% over delay-and-sum beamforming and an increase of 26.5% over superdirective beamforming using six microphones.