Low bit-rate speech coding by perceptually optimized noise excitation modulation

A novel low bit-rate high-quality speech coding technique is presented based on a perceptually optimized signal reconstruction method. According to this parametric speech model, the signal's spectral envelope is reconstructed from non-linear spectral filtering of an excitation signal, which is a combination of a random broadband noise signal with a number of discrete spectral pulses extracted from the original speech using a perceptual model. This general coding platform allows variable bit-rate implementations, starting from 1.9 kbit/s, at which sufficient intelligibility (more than 92%) was measured, while at higher bit-rates (2.8 kbit/s) intelligibility scores were better than 94% with sufficient naturalness in the coded speech. In all cases, the complexity of the proposed system is very low. (C) 1997 Elsevier Science B.V.