On psychoacoustic noise shaping for audio requantization

Signal requantization to reduce the word-length of an audio stream introduces distortions. Noise shaping can be applied in combination with a psychoacoustic model in order to make requantization distortions minimally audible. The psychoacoustically optimal noise shaping curve depends on the time-varying characteristics of the input signal. Therefore, the noise shaping filter coefficients are to be computed and updated on a regular basis. In this paper, we present a least squares theory for optimal noise shaping of audio signals. It provides a shorter and more straightforward proof of known properties, and in contrast with the standard theory, it does show how noise shaping filters that attain the theoretical optimum can be designed in practice.