Patent ID: 7783481

Claim:
A noise reduction apparatus, implemented by a computer system, having an analysis unit for analyzing a frequency of an input voice signal and converting the signal into a signal of a frequency area, a suppression unit for suppressing the signal of the frequency area, and a synthesis unit for synthesizing and outputting a suppressed signal of a time area using the suppressed signal of the frequency area, comprising: a voice information estimation device to estimate as voice information, using output of the analysis unit, information for use as basic information in calculating a suppression gain of a signal, which is information corresponding to at least pure voice element excluding a noise element in an input voice signal; and a suppression gain calculation device to calculate the suppression gain based on output of said voice information estimation device and the analysis unit, and providing a calculation result for the suppression unit; wherein the voice information estimation device estimates an average power value, as a voice signal, indicating the number of samples totalized from a largest power as a predetermined ratio of a number of samples in a power distribution in each frequency of pure voice for a plurality of input voice signal frames, and a power Pki of a current frame for each frequency and a spectrum power average value PMAXki at a predetermined higher rate in a spectrum power of a noise superposed voice signal, that is, a voice information output by the voice information estimation device are used to calculate the suppression gain Gki as follows: dki=P MAX ki−Pki 0≦i<N Gki=f ( dki ) 0 ≦i<N.