A multiplicative distortion Hm (cep) is subtracted from a voice HMM 5, a multiplicative distortion Ha (cep) of the uttered voice is subtracted from a noise HMM 6 formed by HMM, and the subtraction results Sm(cep) and äNm (cep) -Ha (cep) ü are combined with each other to thereby form a combined HMM 18 in the cepstrum domain. A cepstrum R &circ& a(cep) obtained by subtracting the multiplicative distortion Ha (cep) from the cepstrum Ra(cep) of the uttered voice is compared with the distribution R &circ& m(cep) of the combined HMM 18 in the cepstrum domain, and the combined HMM with the maximum likelihood is output as the voice recognition result. <IMAGE>
HMM-based noisy speech recognition