PNS

With traditional transform-based coding, atonal (noise) parts of the sound are usually very distorted. This results from the noise energy being represented by many transform coefficients of low magnitudes which are randomly being cut-off by the quantizer, which produces specific metallic-like distortions. Perceptual Noise Substitution is an optional tool which encodes the noise-like sounds in a very efficient way. For the listener it is irrelevant that the noise reproduced is not the original as long as it has the same spectral properties and intensity. PNS detects noise in the encoder and removes it from the signal. At the decoder side, another noise is generated artificially, with the same spectral characteristics and equivalent energy.

MPEG audio coder with Perceptual Noise Substitution tool

Audio demo: