Harmonic Enhancement with Noise Reduction of Speech Signal by Comb Filtering

As single channel speech enhancement, common methods based on short-time spectral amplitude estimation such as spectral-subtraction and Wiener filtering are considered to be simple and effective for suppressing the additive noise in noisy environments. However, these techniques may distort the high frequency harmonics of speech, which are important to the language understanding. To solve this problem, we propose a new approach. It works by using a comb filter in time domain after Wiener filtering. With the harmonics of voiced speech enhanced and most of the noise suppressed, another comb filter in frequency domain is used to recalculate the suppression gain function, renewing the high frequency harmonics that have been compressed. This new method is theoretically derived, and experimentally demonstrates an improvement for harmonic enhancement and noise reduction.