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
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.