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A Pseudo Glottal Excitation Model for the Linear Prediction Vocoder with Speech Signals Coded at 1.6 kbps
Hwai-Tsu HU Fang-Jang KUO Hsin-Jen WANG
IEICE TRANSACTIONS on Information and Systems
Publication Date: 2000/08/25
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Speech and Hearing
speech coding, vocoder, pseudo glottal excitation, linear prediction,
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This paper presents a pseudo glottal excitation model for the type of linear prediction vocoders with speech being coded at 1.6 kbps. While unvoiced speech and silence intervals are processed with a stochastic codebook of 512 entries, a glottal codebook with 32 entries for voiced excitation is used to describe the glottal phase characteristics. Steps of formulating the pseudo glottal excitation for one pitch period consist of 1) applying a polynomial model to simulate the low-frequency constituent of the residual, 2) inserting a magnitude-adjustable pulse sequence to characterize the main excitation, and 3) introducing turbulent noise in series with the resulting excitation. Procedures are described for codebook construction in addition to analysis and synthesis of the pseudo glottal excitation. Results in a mean opinion score (MOS) test show that the quality produced by the proposed coder is almost as good as that by 4.8 kbps CELP coder for male utterances, but the quality for female utterances is yet somewhat inferior.