Continuous speech recognition in noise using spectral subtraction and HMM adaptation

This paper describes a scheme fur robust speech recognition at very poor signal to noise ratios. It consists of a continuous spectral subtraction (CSS) scheme integrated into a parallel model combination (PMC) compensation framework. In this CSS-PMC scheme, a smoothed estimate of the long term spectrum is continuously calculated and subtracted from the signal. At the same time, the HMMs are compensated using PMC for the signal distortion caused by the CSS stage. The paper presents an evaluation of the CSS-PMC approach using the Noisex 92 database. The results show high recognition performance for very noisy environments. For example, for the Lynx helicopter noise, CSS-PMC gives 97% accuracy at 0 dB SNR