noise shaping


noise shaping

(communications)Spectral noise transformation in aquantisation processes. Noise is "colourised" in the time domain an/or frequency domain by adding parts of theprevious sample. The SNR bandwidth and SNR time integralstay the same, so some noise decreases, some increases, butoverall noise always increases.

An example of noise shaping in the frequency domain isquantisation of samples on a Compact Disc to reduce noisebelow -98 dB. The are different algorithms with slightlydifferent filters, e.g. Super Bitmapping, 4D Recording.

A time domain example is MPEG-4 AAC TNS, which is a methodto enhance quality by temporal forming of the noise in atransform block.