A Blind Channel Identification-Based Two-Stage Approach to Separation and Dereverberation of Speech Signals in a Reverberant Environment

Blind separation of independent speech sources from their convolutive mixtures in a reverberant acoustic environment is a difficult problem and the state-of-the-art blind source separation techniques are still unsatisfactory. The challenge lies in the coexistence of spatial interference from competing sources and temporal echoes due to room reverberation in the observed mixtures. Focusing only on optimizing the signal-to-interference ratio is inadequate for most if not all speech processing systems. In this paper, we deduce that spatial interference and temporal echoes can be separated and an MIMO system will be converted into SIMO systems that are free of spatial interference. Furthermore we show that the channel matrices of these SIMO systems are irreducible if the channels from the same source in the MIMO system do not share common zeros. Thereafter we can apply the Bezout theorem to remove reverberation in those SIMO systems. Such a two-stage procedure leads to a novel sequential source separation and speech dereverberation algorithm based on blind multichannel identification. Simulations with measurements obtained in the varechoic chamber at Bell Labs demonstrate the success and robustness of the proposed algorithm in highly reverberant acoustic environments.