SPEECH CODING SYSTEM AND METHOD INCLUDING HARMONIC GENERATOR HAVING A PITCH-RELATED ADAPTIVE RANDOMIZED PHASE OFF-SETTER

A speech coding system (10) and associated method rely on a speech encoder (15) and a speech decoder (20). The speech decoder (20) includes a Linear Predictive Coding (LPC) filter (90) having an input and an output. The LPC filter (90) provides synthesized speech at its output in response to voiced and unvoiced excitation provided at its input. A harmonic generator (70) for providing voiced excitation to the input of the LPC filter includes a pitch-related randomized adaptive phase off-setter. The adaptive phase off-setter off-sets the harmonic phases of the voiced excitation in accordance with the fundamental pitch frequency of respective frames of speech. The system and method thereby reduce perceived buzziness of synthesized speech provided at the output of the LPC filter.