NOISE REDUCTION FOR AUTOMATIC SPEECH RECOGNITION

摘要

Disclosed herein is a noise reduction method for automatic speech recognitionl. A noise reduction method for automatic speech recognition, including: computing a magnitude spectrum (Yk(m) of a noisy speech containing a clean speech to be recognized and noise affecting the clean speech; computing a power spectrum (||Yk(m||<2>) of the noisy speech; computing an estimate ( ||Xk (m) ||<2> of a power spectrum of the clean speech; computing an estimate ( Dk (m||<2>) of a power spectrum of the noise; computing an estimate (xik(m)<2>) of an a priori signal-to-noise ratio as a function of the estimate (||Xk,( m)¦<2>) of the power spectrum of the clean speech and the estimate (||Dk(m)¦<2 >of the power spectrum of the noise; computing an estimate (gammak(m) ) of an a posteriori signal-to-noise ratio as a function of the power spectrum (||Yk(m) ||<2>) of the noisy speech and the estimate (||Dk(m) ||<2>) of the power spectrum of the noise; computing an attenuation gain (Gk(m)) as a function of the estimate (xik(m)) of the a priori signal-to-noise ratio and the estimate (gammak(m)) of the a posteriori signal-to-noise ratio; and computing an estimate (||Xk(m) ) of a magnitude spectrum of the clean speech as a function of the magnitude spectrum (||Yk(m) ) of the noisy speech and the attenuation gain (Gk(m)). Computing the estimates (xik(m),gammak(m)) of the a priori and the a posteriori signal-to-noise ratios includes computing a noise weighting factor (alpha(m)) for weighting the estimate (Dk(m)<2>) of the power spectrum of the noise in the computation of the estimates (xik(m),gammak(m)) of the a priori and the a posteriori signal-to-noise ratios; computing a spectral flooring factor (beta(m)) for flooring the estimates (xik(m), gammak(m))of the a priori and the a posteriori signal-to-noise ratios; and computing the estimates (xik(m), gammak(m)) of the a priori and the a posteriori signal-to-noise ratios also as a function of the noise weighting factor (alpha(m) and the spectral flooring factor (beta(m)).