A high-performance, perceptual audio compression coding scheme which exploits the properties of the human ear and brain while trying to maintain perceived sound quality. MPEG-1 and 2 define a family of three audio coding systems of increasing complexity and performance – Layer-1, Layer-2 and Layer-3. MP3 is shorthand for Layer-3 coding. MPEG defines the bitstream and the decoder but, to allow for future improvements, not an encoder. MP3 is claimed to achieve ‘CD quality’ at 128-112 kb/s – a compression of between 10 and 12:1. Not all listeners agree with that.

See also: Auditory masking