The recently released iZotope Insight metering suite helps you ensure your audio is fully compliant with current loudness standards. With this in mind, we decided to put together a short summary of the recent history of loudness and how it has led us to where we are today.
The battle of loudness has been going since before the 1980s. Back before compact discs were released, vinyl was the primary medium. Due to physical restrictions involved in cutting audio to vinyl – there was only ‘so loud’ audio could go, before the track started to distort.
This meant that, although some production companies and mastering engineers were able to push the level harder then others – to make their track standout over the other hits out at the time, there was a natural maximum level.
Once compact discs were released in the collaboration between Philips and Sony in 1980, the previous physical limitations were no longer present in the digital realm.
Production companies and mastering engineers were now able to push the music harder than ever before. This meant that eventually standards had to be introduced – to create an acceptable standard which an album or a single track has to meet before it can be released.
In TV and radio broadcasting, loudness changes also caused similar issues; with some programs being louder then others, some adverts pushing the volume levels to be noticed over other adverts etc.
In more recent times, the European Broadcasting Union (EBU) has introduced many standards which need to be met before audio can be released to the public. Other international standards have also been release by other governing bodies, from across USA to Japan etc.
In 2011, the EBU revised their standards agreement so that, as well as the average Programme Loudness of a programme/audio signal requiring to meet a set standard, the Loudness Range and the Maximum True Peak Level are also now required to meet a normalised standard. This is in addition to the program’s compliance with other technical limits and as well as meeting each programme/station’s individual aesthetic needs.
The Programme Loudness refers to the integrated loudness over the duration of an entire programme. Programme Loudness Level is the value (in LUFS) of Programme Loudness. The Loudness Range (LRA) is the distribution of loudness within a programme. The Maximum True Peak Level refers to the maximum peak value of the audio signal waveform.
The EBU R 128 standard states that:
- The Programme Loudness Level shall be normalised to a Target Level of -23.0 LUFS. The permitted deviation from the Target Level shall generally not exceed ±1.0 LU for programmes where an exact normalisation to Target Level is not achievable practically (for example, live programmes)
- The audio signal shall generally be measured in its entirety, without emphasis on specific elements such as voice, music or sound effects.
- The measurement shall be made with a loudness meter compliant with both ITU-R BS.1770 and EBU Tech Doc 3341 .
- This measurement shall include a gating method as specified in ITU-R BS.1770 (summarised in EBU Technical Document 3341).
- Loudness Range shall be measured with a meter compliant with EBU Tech Doc 3342 .
- The Maximum Permitted True Peak Level of a programme during production shall be -1 dBTP (dB True Peak), measured with a meter compliant with both ITU-R BS.1770 and EBU Tech Doc 3341.
The EBU further recommends:
- That loudness metadata shall be set to indicate -23 LUFS for each programme that has been loudness normalised to the Target Level of -23 LUFS.
- That loudness metadata shall always correctly indicate the actual programme loudness, even if for any reason a programme may not be loudness normalised to -23 LUFS,
- That audio processes, systems and operations concerning production and implementation should be made in compliance with EBU Tech Doc 3343 .
- That audio processes, systems and operations concerning distribution should be made in compliance with EBU Tech Doc 3344 .