How to Guide
Audio Loudness Monitoring
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What is Loudness?
Overall loudness of a program needs to be maintained within the listening environment. If
there are significant variations between programs or between channels, the user will
invariably have to reach for the remote control to change the volume to a suitable listening
level. This can lead to user frustration as they have to constantly change the volume control
between programs and between channels. The broadcast chain needs to maintain a
suitable average loudness for the various programs they are transmitting.
Loudness is a subjective measurement and is primarily a psychological correlation with the
physical intensity of the audio signal. Different people will perceive the loudness of the
signal differently and therefore a variety of techniques have been used to characterize the
overall loudness of the signal. The ITU-R BS.1770 standard (algorithms to measure audio
program loudness and true-peak audio levels) is one method for measuring loudness within
broadcast environments. The ITU-R BS 1770 standard has been adopted by ATSC within
recommend practice A85 Techniques for Establishing and Maintaining Audio Loudness for
Digital Television and EBU recommendation R128 Loudness normalisation and permitted
maximum level of audio signals.