Audio Broadcast Standards

When it comes to the audio industry standards are crucial whether that is for mastering, distribution, broadcasting or any other frameworks that involve audio. One of the most widely used of these is broadcasting especially for television, film and radio. Broadcasting standards can be confusing as a lot of countries have different standards that they follow.

When it comes to television the standards can be very different depending on the channel that the audio is being used on which can make the audio across multiple channels seem inconsistent. However, through vigorous human testing, in 2006 The International Telecommunication Union published the BS.1770 global standard which many other important broadcast standards are based on. The ITU standard relates to Broadcast Loudness and True-peak Level measurement. The loudness standard is Loudness, K-weighted, relative to Full Scale or LKFS and is designed to enable normalization of audio levels. Loudness Units relative to Full Scale (LUFS) is a synonyms for LKFS though mainly used in Europe while LKFS is mainly used in the US. Loudness UNits or LU is an additional unit that is internationally used and describes loudness level differences. The scale goes further into the negative value as the audio gets softer with 1dB being equivalent to 1 difference in LKFS value. For example -26LKFS is 1dB quieter than -25LKFS.

Previously most channels in Australia used to use an analogue Peak Program Meter and a VU meter to set the standard for audio broadcasting in television though while these meters may show equal levels the audio can be different in perceived loudness which can be affected by tonal balance and especially the degree of compression and equalization. Commercials on certain channels could use this to their advantage by compressing the audio too much and increasing the gain which would make the audio sound louder in turn getting the attention of the viewer though making any other audio seem inconsistent. This would still fall in compliance with the previous standards- OP48.

OP-59 was brought into effect out in January 2013 in a effort to have Australian and New Zealands broadcasts meet the same standards as the U.S and Europe. The OP-59 Standard states that the adopted target for loudness in Australia is -24LKFS. OP-59 also states two different ways to monitor the loudness value of the audio being used. It suggests monitoring the dialogue audio only then monitoring all of the components of the full mix ie, music, sound effects, dialogue etc. This guarantees the audio comes as close to the -24LKFS standard as possible without lowering all of the dialogue due to other loud components of the mix.

Having all countries follow one standard is dire to have a seamless transition from broadcasting a television show in one country then have it broadcast to a different country without any abnormal variations in the audio both in volume and quality.

References:

http://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BS.2054-2-2011-PDF-E.pdf

http://www.freetv.com.au/media/Engineering/Free_TV_OP59_Measurement_and_Managemnt_of_Loudness_for_TV_Broadcasting_Issue_2_December%202012.pdf

http://www.sandymilne.com/op-59-and-loudness-standards-for-australian-tv/

http://loudness.hku.nl/Peak_and_LKFS_-_Grimm_ea.pdf

http://www.tcelectronic.com/loudness/broadcast-standards/

https://tech.ebu.ch/docs/r/r128.pdf

This blog addressed LO 10

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