Patent ID: 7606702

Claim:
A speech decoder, comprising: a code separation/decoding unit for restoring a vocal tract characteristic and a vocal source signal by separating a received voice code; a formant estimation unit for estimating a plurality of formants in said vocal tract characteristic; an amplification ratio calculation unit for calculating a plurality of amplification ratios, each corresponding to each of the plurality of estimated formants, for the vocal tract characteristic based on the plurality of estimated formants; an emphasis unit for emphasizing the vocal tract characteristic based on the calculated plurality of amplification ratios; and a signal synthesis unit for outputting a voice signal by synthesizing the modified vocal tract characteristic modified by the emphasis unit and the vocal source signal obtained from the voice code, wherein said formant estimation unit estimates a plurality of pairs, each having a formant frequency and a formant amplitude at said formant frequency, each of the plurality of pairs corresponds to each of the plurality of estimated formants, said amplification ratio calculation unit calculates a constant amplification reference power from said vocal tract characteristic and determines the plurality of amplification ratios of the respective plurality of formants so as to match the formant amplitude of each pair of the plurality of pairs with the same constant amplification reference power, and said emphasis unit emphasizes the vocal tract characteristic by using each of the plurality of amplification ratios of each of the respective plurality of formants.