关键词: 小波变换, 语音信号, 阈值, 去噪

Abstract: The theory of wavelet denoising is analysised,and a wavelet speech enhancement method based on improved－threshold is proposed according to the characteristics of random noise wavelet transform on the different scale and the relationship between the noise Lipschitz exponents and its wavelet transform maximum modulus,also considering the unvoiced and voiced speech’s features．A parameter can be adjusted properly in the new threshold function to obtain the best estimations of the wavelet coefficients which enables this function to become a more general case incorporating the hard and soft threshold.Using improved－threshold to process the wavelet coefficients of the speech containing noise,not only the noise can be removed,but also the quality degradation of the unvoiced sounds can be prevented．Simulation results demonstrate the method is very effective in speech enhancement．

Key words: wavelet transform, speech signal, threshold, denoising