Noise suppression method and device thereof

In a method for suppressing noise by a spectrum subtraction method, it is intended to increase the noise suppression performance by satisfying both of frequency resolution that is necessary for a noise estimation spectrum and time resolution that is necessary for a noise suppression spectrum. The signal length of an observation signal that is extracted to analyze a spectrum of the observation signal to be used for calculation for estimation of a noise spectrum is set longer than the signal length of an observation signal that is extracted to analyze a spectrum of the observation signal as a minuend from which to subtract the noise spectrum.