Perceptual coding of narrowband audio signals at 8 kbit/s

This paper proposes a VQ-based transform coding scheme for audio signals (sampled at 8 kHz) at very low bit rates. This coder uses a new perceptually based distortion measure, which takes into account the energy of audible noise, in both training the codebooks and selecting the best codewords. An adaptive bit allocation strategy based on the distribution of the energy of the transform coefficients above the masking threshold is employed to assign more bits to perceptually important critical bands. This coder delivers good quality for most audio signals at 1 bit/sample