SPEECH ENHANCEMENT USING SPECTRAL SUBTRACTION WITH WAVELET TRANSFORM

For speech enhancement based on spectral estimation/analysis, an analy tic technique by which speech signals can he easily distinguished from noise is desired. The wavelet transform (WT) is an analysis tool for which various types of basis functions can be used. By selecting a pro per fundamental wavelet. speech energy can be effectively localized in the space transformed by the WT. In this article, we apply the WT to the spectral subtraction technique, originally defined as using the sh ort-time Fourier transform (STFT), and evaluate the effectiveness of i ts outcome. Considering the structure of the human voice, we use Gabor and Daubechies wavelets as well as a decaying sinusoid as the fundame ntal wavelet. The results of computer simulations show that the S/N ra tio was improved by the proposed method employing the decaying sinusoi d as compared with conventional spectral subtraction. In articulation tests with Japanese nonsense monosyllables, however, no significant di fference could be observed. (C) 1998 Scripta Technica.