Patent ID: 7349841

Claim:
A noise suppression device comprising: time/frequency conversion means for frequency-analyzing a frame of an input signal and converting the frame of the input signal to an input signal spectrum and a phase spectrum; noise likeness analysis means for calculating a noise likeness signal as an index of whether the frame of the input signal contains noise or speech; noise spectrum estimation means for receiving the input signal spectrum obtained by the time/frequency conversion means, calculating a first subband-based input signal average spectrum from the input signal spectrum, and updating a subband-based estimated noise spectrum, which is estimated from past frames of the input signal, based on the calculated first subband-based input signal average spectrum and on the noise likeness signal calculated by the noise likeness analysis means; subband SN ratio calculating means for receiving the noise likeness signal calculated by the noise likeness analysis means, the input signal spectrum produced by the time/frequency conversion means and the subband-based estimated noise spectrum updated by the noise spectrum estimation means, calculating a second subband-based input signal average spectrum from the received input signal spectrum, calculating a subband-based mixture ratio of the received subband-based estimated noise spectrum to the calculated second subband-based input signal average spectrum based on the received subband-based noise likeness signal, and calculating a subband-based SN ratio on the basis of the received subband-based estimated noise spectrum, the calculated second subband-based input signal average spectrum and the calculated subband-based mixture ratio; spectral suppression amount calculation means for calculating a subband-based spectral suppression amount with respect to the subband-based estimated noise spectrum updated by the noise spectrum estimation means, by using the subband-based SN ratio calculated by the subband SN ratio calculation means; spectral suppression means for carrying out spectral amplitude suppression on the input signal spectrum obtained by the time/frequency conversion means by employing the subband-based spectral suppression amount calculated by the spectral suppression amount calculation means, and thereby presenting an output of noise removed spectrum; and frequency/time conversion means for converting the noise removed spectrum fed from the spectral suppression means to a noise suppressed signal in time domain by using the phase spectrum obtained by the time/frequency conversion means.