Mixed-excited phonetic vocoding at 265 bps

In this paper a phonetic vocoder which synthesizes speech using mixed excitation is presented. The encoder carries out HMM-based speech recognition and pitch analysis, whereas the decoder performs parameter extraction from HMM and builds a mixed excitation using pitch and bandpass voicing strengths. The vocoder at an average bit rate of 265 bit/s reaches good degree of intelligibility, while the use of mixed excitation significantly improves the speech quality with no increase of bit rate when compared with the conventional binary excitation pulse train/random noise.