Compression factor ranging from 2.7 to 24. MPEG audio supports sampling frequencies of 32, 44.1 and 48 KHz. If the power in a band is below the masking threshold, don't encode it. If the level of the 8th band is 60dB, it gives a masking of 12 dB in the 7th band, 15dB in the 9th. MPEG Layers MPEG defines 3 layers for audio.
Basic model is same, but codec complexity increases with each layer.
Psychoacoustic model only uses frequency masking. This models a little bit of the temporal masking.