A Broadcast Engineering Tutorial for Non-Engineers by Skip Pizzi & Graham Jones

Author:Skip Pizzi & Graham Jones [Pizzi, Skip]
Language: eng
Format: epub
ISBN: 9781317906827
Publisher: Taylor and Francis
Published: 2014-04-24T00:00:00+00:00

The CALM Act

Such loudness shifts between program segments are something that the DTV audio system is technically able to accommodate without continual adjustment of the listening volume by television viewers—through a process in the AC-3 audio system called dialog normalization—but industry practice did not always take proper advantage of it. This led to many listener complaints, and ultimately engendered a U.S. law called the CALM Act (for Commercial Audio Loudness Mitigation), along with subsequent FCC regulations enforcing it. Since 2012, U.S. television broadcasters have thereby been bound by law to maintain a fairly consistent loudness across all program segments.

To assist stations in complying with this requirement, new metering systems have been developed that can quantify not just electrical audio levels but also indicate human perception of long-term loudness, using an internationally standardized loudness-assessment algorithm called ITU-R BS.1771. This capability can be used in conjunction with the dialog normalization feature mentioned above to ensure that audio loudness in DTV content remains stable between content segments (in particular, between a television station’s programs and its commercials). Further detail on audio loudness management in DTV broadcasting is provided in Chapter 16.

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