An acoustic signal enhancement method is disclosed. The acoustic signal enhancement method comprises the steps of applying a spectral transformation on a frame derived from an input acoustic signal to generate a spectral representation of the frame, estimating an a posteriori SNR and an a priori SNR of the frame, determining an a priori SNR limit for the frame, limiting the a priori SNR with the a priori SNR limit to generate a final a priori SNR for the frame, determining a spectral gain for the frame according to the a posteriori SNR and the final a priori SNR, and applying the spectral gain on the spectral representation of the frame so as to generate an enhanced spectral representation of the frame. One of the characteristics of the acoustic signal enhancement method is that the a priori SNR limit is a function of frequency.