the present invention relates to a system , method and program for speech recognition . in an embodiment of the invention a method for processing a speech signal consists of receiving a power spectrum of a speech signal and generating a log power spectrum signal of the power spectrum . the method further consists of performing discrete cosine transformation on the log power spectrum signal and cutting off cepstrum upper and lower terms of the discrete cosine transformed signal . the method further consists of performing inverse discrete cosine transformation on the signal from which the cepstrum upper and lower terms are cut off . the method further consists of converting the inverse discrete cosine transformed signal so as to bring the signal back to a power spectrum domain and filtering the power spectrum of the speech signal by using , as a filter , the signal which is brought back to the power spectrum domain .