Adaptive postfiltering for enhancement of noisy speech in the frequency domain

A novel frequency-domain adaptive postfilter for enhancement of noisy speech is presented. The postfilter suppresses the noise in spectral valleys and allows more noise in the formant regions where it is masked by the speech signal. First, the authors perform an LPC (linear predictive coding) analysis of the noisy speech and calculate its log magnitude spectrum. After identifying the formants and spectral valleys, the log magnitude spectrum is modified to obtain the postfilter frequency response. This response has local maxima of equal magnitude at the formant frequencies. Experimental results show that this novel frequency-domain approach results in enhanced speech of better perceptual quality than obtained by a time-domain method. The proposed method is especially efficient in eliminating high frequency noise and in preserving the weaker, high frequency formants in sonorant sounds.