Co-channel speech separation for robust automatic speech recognition: stability and efficiency

A signal-separation front-end based on adaptive decorrelation filtering (ADF) was integrated with an HMM based speaker independent continuous speech recognition system for co-channel speech recognition. The ADF is improved by addressing the adaptation gain for system stability and efficiency: an upper bound of adaptation rate is derived for system stability, and an accelerated sequence of adaptation gain is introduced for system efficiency. The system was evaluated under simulated room acoustic conditions with both time-invariant and time-varying channels. It is shown that the system significantly improved the signal-to-interference ratio and the recognition word accuracy, and that the combination of the derived upper bound for adaptation rate with the accelerated adaptation gain sequence achieved the best performance for system stability and efficiency.