Psychoacoustic noise shaping achieves an effective 120 dB SNR on CD audio

Evidence

Equation 7.15 shows that the quantizer’s error is shaped by the filter function (1  N(z)). It is possible to design this filter to reduce the noise within the most sensitive bit of our hearing range. This technique is used to improve the quality of sounds on a CD. An example is Sony Super Bit Mapping (Akune et al., 1992), which uses psychoacoustic noise shaping to give an effective sig­ nal to noise ratio of 120 dB (20 bits) in our most sensitive frequency range. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2668

Categorization

• XREF: Connects to the reader’s psychoacoustics goal of ‘how life can be interpreted through sound’ — the fact that perceptual masking lets 16-bit media sound like 20-bit.
• CANDY: A compact, shareable fact: CDs leverage your own hearing’s blind spots to sound better than their bit depth.