Introduction to Loudness Standards

An overview of the loudness measurement standards Sonic Atom implements — ITU-R BS.1770, EBU R 128, ATSC A/85, TR-B32, and OP-59.

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ITU BS.1770

The ITU BS.1770 is the most important standard as many other standards are based on it.

The ITU standard concerns Loudness and True-peak Level. The loudness part is based on a Leq measurement (K-weighting), which is a frequency weighting developed by the Communications Research Centre Canada (CRC), a federal research institute in Ottawa.

The True-peak standard was specified by AES SC-02-01.

The standards: ATSC A/85 (US), EBU R128 (Europe), OP-59 (Australia) and TR-B32 (Japan), are based on the ITU standard.

ITU BS.1770 published 2006 (Geneva).

ITU BS.1770-2 published March 2011 (Geneva).

ITU BS.1770-3 published August 2012 (Geneva).

ITU BS.1770-4 published October 2015 (Geneva).

ITU BS.1770-5 published November 2023 (Geneva).

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EBU R128

The PLOUD group, part of The European Broadcasting Union (EBU), defined the R128 standard based on ITU BS.1770.

The R128 standard builds on 4 tech documents: EBU Tech 3341, EBU Tech 3342, EBU Tech 3343 and EBU Tech 3344.

The recommended loudness target is -23 LUFS.

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ATSC A/85

ATSC A/85 was specified by The Advanced Television Systems Committee in 2009 and applies to US broadcast digital television. A/85 is rooted in the ITU-R BS.1770 Loudness and True-peak level standard.

A/85 includes information about calibrated monitoring environments and unlike EBU R128, A/85 is only focused on digital television.

Loudness normalisation target of -24 LKFS.

From March 2013, the A/85 recommended practice prescribes ITU BS.1770 for all programming.

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TR-B32

TR-B32 is a Japanese standard that builds on ITU BS.1770-3 (gate is employed), however, the target level is -24 LUFS/LKFS as opposed to the -23 LUFS target level of the EBU R128 standard.

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OP-59

Operational practice by Free TV Australia. OP-59 is rooted in BS.1770 Loudness and True-peak level.

All short-form programs should be measured using the universal (full mix) method.

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Did you know?

As a rule of thumb, a gated measurement of -23 LUFS/LKFS is roughly equivalent to an un-gated measurement of around -24 LUFS/LKFS — the exact offset depends on programme dynamics.

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