Patent ID: 8412520

Claim:
A noise reduction device for obtaining an output signal whose noise is reduced based on an input signal, the device comprising: a SN ratio obtaining unit configured to obtain a SN ratio as a function of an estimated noise spectrum, and an arithmetic product of an averaged power spectrum of the input signal and a noise likeliness signal, the SN ratio being one of two types of definitions according to values of both the averaged power spectrum of the input signal and the estimated noise spectrum, the first definition being a calculation of a value based on both the estimated noise spectrum and the arithmetic product, and the second definition being a predefined constant, the estimated noise spectrum being estimated based on the averaged power spectrum of the input signal, and the noise likeliness signal being calculated as an index indicating a likelihood that the input signal is noise, and being calculated as a variable ranging from a plurality of values that are larger than 0 and smaller than 1; and an output signal obtaining unit configured to obtain an output signal whose noise is reduced based on the input signal and the SN ratio obtained by the SN ratio obtaining unit.