Patent ID: 7788093

Claim:
A noise reduction device comprising: an input signal spectrum obtaining unit configured to obtain an input signal spectrum by a subband unit based on a current frame of an input signal; an averaged spectrum obtaining unit configured to obtain an averaged spectrum of the input signal by averaging the input signal spectrum; an estimated noise spectrum obtaining unit configured to obtain an estimated noise spectrum estimated based on a past frame of the input signal by the subband unit; an SN ratio obtaining unit configured to obtain an SN ratio by the subband unit, based on the averaged spectrum of the input signal obtained by the averaged spectrum obtaining unit, the estimated noise spectrum obtained by the estimated noise spectrum obtaining unit, and a function of the averaged spectrum of the input signal obtained by the averaged spectrum obtaining unit and the estimated noise spectrum obtained by the estimated noise spectrum obtaining unit; a reduction coefficient obtaining unit configured to obtain a reduction coefficient by the subband unit based on the SN ratio obtained by the SN ratio obtaining unit, the reduction coefficient being used for reducing noise of the input signal; and a noise reduction signal obtaining unit configured to obtain a signal whose noise is reduced based on the input signal and the reduction coefficient obtained by the reduction coefficient obtaining unit.