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No more noisy television adverts?
New ITU standard aims to keep sound volumes constant in broadcasts
photo credit: Shutterstock

A new draft ITU standard should help put an end to annoying variations in sound volume when watching television — to the benefit of viewers and broadcasters around the world. People are often irritated when there is a sudden change in the sound level if they switch channels, or when the commercials are shown. This means that viewers must repeatedly adjust the volume control.

Variations in loudness have become more noticeable with the advent of digital broadcasting and its multiplicity of channels. Also, although viewers might erroneously blame the variations on careless sound technicians or deliberate policies by broadcasters, there are a number of technical factors that are not easily controlled in the studio. A technician registers sound levels according to the strength of the electrical signal — which is not a direct measure of how loud the television will sound in your living room. Volume is also affected by such things as the degree of dynamic range compression in the audio signal.

To rectify the problem, broadcasters need a meter which displays “loudness” (rather than the strength of an electrical signal), in line with an agreed, standard setting, so that sound technicians everywhere can make the same adjustment. At its meeting in November 2009, Study Group 6 of ITU’s Radiocommunication Sector (ITU–R) agreed a draft new Recommendation outlining how sound levels should be measured in programmes that are exchanged internationally. It offers a setting termed the “target loudness”, which is given a numerical value. The technique will allow sound to be maintained at a constant level and so make television viewing more pleasurable.

Entitled “Operational practices for loudness in the international exchange of digital television programmes”, the draft Recommendation will be submitted to national telecommunication administrations for approval. It complements existing Recommendation ITU–R BS.1770, which describes features of the meter that should be used by broadcasters to measure loudness.


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