Volume control for audio signals

Abstract

A motion picture soundtrack reproduction system has a center front soundtrack channel and a plurality of other soundtrack channels. A volume control adjusts the gain of all the channels. The volume control has a range of settings from a minimum to a maximum, the gain of the center front channel having substantially a first relationship to the volume control settings and the gain of the other channels having substantially a second relationship to the volume control settings, the relationships being such that for a range of volume control settings less than a first setting the gain of the center front channel remains substantially constant while the gain of the other channels decreases as the setting decreases or decreases more gradually than the gain of the other channels as the setting decreases.

Description

TECHNICAL FIELD[0001]The invention relates generally to the processing of audio signals. More particularly, the invention relates to control of the loudness of motion picture soundtracks when reproduced.BACKGROUND ART [0002]In the mid-1970s, Dolby Laboratories introduced a calibration recommendation for monitor levels in movie soundtracks (“Dolby” is a trademark of Dolby Laboratories, Inc.). A pink noise reference signal was used in the record chain to adjust the audio monitor level to 85 dBc. All theatres equipped for playback of the new stereo optical soundtracks were set up such that an equivalent pink noise signal in a soundtrack channel generated the same 85 dBc with the playback volume control (fader) set to the calibrated setting. This meant that theatres playing films at the calibrated volume control setting (a setting of “7” in a range of “0” to “10” on most cinema processors) reproduced the same loudness level selected by the film director and audio engineers in the dubbin...

AI Technical Summary

Benefits of technology

[0015]The invention provides for reducing the maximum loudness, and thereby avoiding complaints, while maintaining the acoustic level of the center front containing dialogue and requiring only one user-operated control. According to an embodiment of the invention, the cinema equipment is designed and installed in the conventional manner to the extent that with the volume control nominally at its standard setting, each of the reproduced soundtrack channels has a respective gain that produces a respective standard acoustic level in response to a signal having a respective standard reference level in the channel, thus matching the standard levels in a film mixing room. Thus, when calibrated, the playback system with its volume control at the standard setting has an apparent loudness that is substantially the same as that intended by the film mixer. However, in accordance with the present invention, if the volume control is turned down below the standard setting in response to actual (or expected) complaints from the audience, over a limited range of settings all channels except the center front are attenuated equally, but the center front is reduced by a smaller degree (or not at all). The effect is not only a reduction in the overall loudness but an increase in the proportionate contribution of the center front channel, with a potential improvement in intelligibility when the other channels are loud. Optionally, after some degree of changing the balance of the center front to other channels down to a setting below the standard setting, for further lowering of the settings all channels are attenuated equally, maintaining fixed the altered balance.

Problems solved by technology

Some cinemas have their volume control permanently turned down to such settings because projectionists operating multiplexes with many screens showing different movies simultaneously don't have the time or cannot be bothered to set the controls differently for different movies.

A feature film played with a loudness 6 dB below the calibrated level may have serious dialogue intelligibility problems and very quiet sounds may become inaudible.

In addition, it is possible that the increased use of headroom from Dolby A-type to Dolby SR and digital releases has not been matched by a corresponding increase in power amplifier and loudspeaker capability.

The resultant distortion from overloaded equipment may well exacerbate the loudness problems of recent soundtracks, causing increased incidence of complaints.

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