Psychoacoustic quantization is the sole lossy stage in audio coding.
Evidence
A psychoacoustic quantization stage which allocates bits to the various components in the audio signal in a manner that has the minimum subjective distortion. Again, in order to do this it has to send additional side information to the decoder, such as the number of bits allocated to each signal component. This is the only stage that removes information from the signal and is therefore the only lossy stage in the whole process. It is this stage that makes the difference between a lossy and a lossless audio coding system. Note that although the decoder stage works in reverse to provide real audio levels at the levels quantized by the coder, it cannot restore the information that has been thrown away by the encoding quantizer.
— David Howard, Jamie Angus, coustics and Psychoacoustics, 2582
Categorization
DEFINE: Clarifies what makes a codec lossy versus lossless: only the quantization stage discards information, and the decoder can never restore it.
corroborated: 2 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 2582
XREF: connects to: Psychoacoustic quantization is the only stage in audio coding that removes signal information; Lossy coding exploits psychoacoustic models to make removed information inaudible — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2581; Psychoacoustic models govern which audio information can be discarded unnoticed (+1 more)