Hmm-regularization for Nmf-based Noise Robust Asr

In this work we extend a previously proposed NMF-based technique for speech enhancement of noisy speech to exploit a Hidden Markov Model (HMM). The NMF-based technique works by finding a sparse representation of specrogram segments of noisy speech in a dictionary containing both speech and noise exemplars, and uses the activated dictionary atoms to create a time-varying filter to enhance the noisy speech. In order to take into account larger temporal context and constrain the representation by the grammar of a speech recognizer, we propose to regularize the optimization problem by additionally minimizing the distance between state emission probabilities derived from the speech exemplar activations, and a posteriori state probabilities derived by applying the Forward-Backward algorithm to the emission probabilities. Experiments on Track 1 of the 2nd CHiME Challenge, which contains small vocabulary speech corrupted by both reverberation and authentic living room noise at varying SNRs ranging from 9 to -6 dB, confirm the validity of the proposed technique.