Calculating and adjusting the perceived loudness and/or the perceived spectral balance of an audio signal
AssigneeDolby Laboratories Licensing Corporation
InventorAlan Jeffrey Seefeldt
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Abstract
The invention relates to the measurement and control of the perceived sound loudness and/or the perceived spectral balance of an audio signal. An audio signal is modified in response to calculations performed at least in part in the perceptual (psychoacoustic) loudness domain. The invention is useful, for example, in one or more of: loudness-compensating volume control, automatic gain control, dynamic range control (including, for example, limiters, compressors, expanders, etc.), dynamic equalization, and compensating for background noise interference in an audio playback environment. The invention includes not only methods but also corresponding computer programs and apparatus.
Claims68
A method for controlling a particular loudness characteristic of an audio signal, wherein the particular loudness characteristic is either a specific loudness, which is a measure of perceptual loudness as a function of frequency and time, or a partial specific loudness, which is a measure of perceptual loudness of the signal in the presence of a secondary interfering signal as a function of frequency and time, comprising the steps
- a) calculating a target specific loudness,
- b) deriving frequency- and time-variant modification parameters usable for modifying the audio signal in order to reduce the difference between the particular loudness characteristic and the target specific loudness, and
- c) applying the modification parameters to the audio signal to reduce the difference between the particular loudness characteristic and the target specific loudness.
An apparatus for controlling a particular loudness characteristic of an audio signal, wherein the particular loudness characteristic is either a specific loudness, which is a measure of perceptual loudness as a function of frequency and time, or a partial specific loudness, which is a measure of perceptual loudness of the audio signal in the presence of a secondary interfering signal as a function of frequency and time, comprising
- means adapted to receive from a transmission or reproducing from a storage medium an audio signal and frequency- and time-variant modification parameters for modifying the audio signal, and to modify the audio signal in response to the received modification parameters so as to reduce the difference between the particular loudness characteristic of the audio signal and a given target specific loudness,
- wherein the modification parameters are obtainable by calculating said target specific loudness, and deriving said frequency- and time-variant modification parameters usable for modifying the audio signal in order to reduce the difference between the particular loudness characteristic and the target specific loudness.
Dependencies are inferred from the claim text.