Patent ID: 8761415
Filing Date: 2014-06-24
Classification: H03G

Abstract:
1. 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 a plurality of frequency bands of the audio signal that, 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 there are three or more frequency bands 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 response 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 in the logarithmic domain that reduces monotonically below the anchor band, 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.