Harmonic coding at 4.8 kb/s

A harmonic coder designed for operation at 4.8 kb/s is presented. Sinusoidal modeling of speech is reviewed and the use of harmonically related frequencies is extended to unvoiced and transition regions. The estimation of the fundamental frequency with emphasis on the fine tuning of the pitch estimates is discussed. The structure of the 4.8-kbit/s harmonic coder is described, and a detailed discussion of phase quantization issues is presented. Experimental results are presented which reveal a reverberant character in many speech utterances and difficulties in some classes of sounds (plosives, liquids, and voiced fricatives). These distortions are mostly produced by the quantization of phase, but they are also explained by the difficulties of the sinusoidal analysis/synthesis in transition regions when the frame length is large