基于新阈值函数和自适应阈值的 小波包语音增强研究.

Aiming at overcoming the drawbacks that speech enhanced by traditional wavelet packet speech enhancement method had severe distortion, this paper proposed a wavelet packet speech enhancement method based on adaptive threshold and a novel thresholding function. The proposed method windowed and framed noisy speech in wavelet packet domain. Then it calculated probability of existance of speech in each frame based on cross-correlation values of the fast Fourier transform power spectrum of two adjacent frames. Finally it obtained adaptive threshold by adjusting traditional universal threshold accroding to the probability, the adaptive threshold was small in speech distributed frames and large in the speech absence frames, which could preserve speech as far as possible at the same time of removing noise in a greater degree, thus reduced speech distortion. This paper also designed a novel thresholding function, which overcame the drawbacks that traditional hard thresholding function was discontinuous and soft thresholding function brought fixed bias in final speech, to further reduce speech distortion. Extensive simulations were carried out using the TIMIT and NOISEX-92 databases to evaluate the effectiveness of the proposed method. And both subjective and objective evaluations prove that the proposed method has a better performance in enhancing noisy speech, and speech enhanced by proposed method has less speech distortion and better auditory effect. [ABSTRACT FROM AUTHOR]