Patent ID: 8891789

Claim:
A method for adjusting the loudness of an audio signal while reducing changes in its perceived spectral balance, comprising applying the audio signal to a dynamically-controllable filter having a high-frequency response characteristic and a low-frequency response characteristic, receiving dynamically-changing information as to the desired gain in each of three or more frequency bands of the audio signal which desired gain, when applied to the audio signal, tends to preserve perceived spectral balance as the loudness of the audio signal is varied, the information being in response to the audio signal and a desired loudness, wherein the three or more frequency bands are in juxtaposition with one another including an anchor band generally between the lower end of the frequency range in which the high-frequency response characteristic varies and the upper end of the frequency range in which the low-frequency response characteristic varies, a top band at the upper end of the frequency range in which the filter's controllable high frequency response characteristic varies, and at least one band between the anchor band and the top band, and dynamically controlling said filter in response to said information, wherein the high-frequency response characteristic is a variable shelf filter response and the low-frequency response characteristic is a variable-slope response that has a boost/attenuation, the variable shelf filter response being controlled in response to the desired gain in each of said three or more frequency bands and the variable-slope response being controlled in response to the desired gain in said anchor band.