Microphone array sub-band speech recognition

This paper proposes the integration of sub-band speech recognition with a microphone array. A broadband beamforming microphone array allows for natural integration with sub-band speech recognition as the beamformer is typically implemented as a combination of band-limited sub-arrays. In this paper, rather than recombining the sub-array outputs to give a single enhanced output, we propose the fusion of separate hidden Markov models trained on each subarray frequency band. In addition, a dynamic sub-band weighting scheme is proposed in which the crossand auto-spectral densities of the microphone array inputs are used to estimate the reliability of each frequency band. The microphone array sub-band system is evaluated on an isolated digit recognition task and compared to the standard full-band approach. The results of the proposed dynamic weighting scheme are compared to those obtained using both fixed equal sub-band weights, as well as optimal sub-band weights calculated from a priori knowledge of the correct results.