Abstract: Aiming at wavelet threshold denoising，for the issue of signal being sensitive oscillation after the treatment of hard-threshold functions and the issue of signal? being over-distortion after the treatment of soft-threshold functions，a new threshold function based on μ law fitting is put forward.According to the different singularities between speech signals and noises for the different wavelet scales，in another words，based on the facts that modulus of wavelet transform coefficients of speech signals increases while the wavelet transform coefficients of noises decreases by the increasing of wavelet scales，an adaptive thresholds is put forward.It is proved by experiment that definition and intelligibility of voice are obviously increased by enhancing of this new calculation method.

Key words: speech enhancement, wavelet transform, threshold de-noising, μ law fit, adaptive thresholding

摘要： 针对小波阈值去噪法，硬阈值函数处理后信号易产生振荡，软阈值函数处理后信号的失真大等问题，提出了一种基于μ律拟合的新阈值函数。针对语音信号和噪声在不同小波尺度下具有不同的奇异性，即语音信号的小波变换系数的模值随尺度的增加而增加;噪声的小波变换系数的模值随尺度的增大而减小，提出了一种自适应阈值。实验表明，经新算法增强后语音的清晰度和可懂度有了明显的提高。

关键词: 语音增强, 小波变换, 阈值去噪, μ律拟合, 自适应阈值