Speech Enhancement by Overweighting Gain with Nonlinear Structure in Wavelet Packet Transform

A sound quality enhancement method by overweighting gain of a nonlinear structure in a wavelet packet area is provided to restrain the generation of musical noise efficiently and ensure reliable intelligibility in an enhanced voice. A sound quality enhancement method by overweighting gain of a nonlinear structure in a wavelet packet area comprises the following steps of: generating a converting signal that a voice signal polluted by noise is converted by UWPT(Uniform Wavelet Packet Transform); calculating a relative size difference, which is an identifier for calculating a relative difference between the amount of noise existing in a sub band and the amount of a voice polluted by noise; calculating the overweighting gain of the nonlinear structure from the relative size difference; calculating a transformed time-varying gain function based on an LSL(Least-Squares Line) algorithm; and performing spectral subtraction using the transformed time-varying gain function.