What are the current best practises for measuring programme loudness?
Master Reference documentation relating to EBU and ITU Recommendations that relate to loudness measurement techniques and algorithms can be found at :
Loudness measurement techniques apply:
- Channel filtering (K-Weighting)
- Channel Summing
- Channel Weighting
- Level Gating
- RMS integration algorithm
True-Peak Measurement techniques apply:
- Signal up-sampling
Loudness measurement provides three different measurements:
- Momentary - Maximum value of all momentary loudness values that are measured every 100 ms in an audio range of 400 ms
- Short-Term - Loudness that is measured every second on an audio block of 3 seconds
- Integrated - Average loudness that is measured over the whole track
Loudness is measured in "Loudness Units" referenced to "Full Scale", aka "LUFS". (Previous version of the recommendation referenced LKFS which referenced the "K-Weighting" applied to each channel in the measurement algorithm)
The loudness range measures the dynamic range over the whole title in LU (Loudness Units). It reports the ratio between the loudest and the quietest non-silent sections. The audio is divided into small blocks. Every second there is one audio block, and each block lasts 3 seconds so that the analyzed blocks overlap.
The top 10 % of the quiet blocks and the top 5 % of the loud blocks are excluded from the final analysis. The calculated loudness range is the ratio between the loudest and quietest remaining audio blocks. This measurement helps you to decide if and how much compression or expansion you can or should apply to the audio.
Various products are available to provide loudness measurement and metering (in no particular order of preference)
- Waves WLM
- TC Electonic
- Izotope Insight
- NuGen VisLM / Audio Loudness Toolkit