IMPROVING AUDIO CODECS BY NOISE SUBSTITUTION

Adaptive transform coding and adaptive subband coding are widely used methods for high-quality audio coding. Both coding schemes primarily u se masking effects of the human auditory system for data-rate reductio n. A further reduction can be achieved by coding noisy and tonal signa l components separately. Methods to distinguish between tonal and nois y audio components in the time domain, the frequency domain, and the s ubbands are described. Combinations of these coding schemes with adapt ive transform coding and adaptive subband coding are presented. A high ly efficient implementation of adaptive subband coding using noise det ection in subbands is proposed, and results of this coding scheme are given.