LUFS Metering
Last Edited: Dec 24, 2023
Back in the days of analog recording, meters displayed electrical levels to represent the audio level. Today’s digital technology enables alternative types of metering. For example, unlike the human ear, which has different sensitivities to sound at varying frequencies (we perceive volume changes in mid-range frequencies much more acutely than at low and high frequencies), old-school level meters can’t distinguish between frequency ranges. To account for this, engineers created an entirely new metering scale, called LUFS (Loudness Units Full Scale), to account for how we perceive loudness, not just average levels or peaks. There’s a further refinement called LKFS, which uses weighting to account for differences in frequency response.
Loudness Units Full Scale
LUFS is a measurement of loudness units designed by the ITU-R BS.1770 recommendation regarding the loudness and true-peak level of audio. A loudness unit is identical to a decibel. However, the loudness units measurement system is weighted to the real perception of audio rather than just the electrical signal. Ultimately, this has far more real-world application. It makes the balancing of multiple audio sources far more manageable. This is because you’re metering the final product rather than the electrical source of varying projects.
Practical Use
An excellent example of the practical use of LUFS metering would be browsing through the eclectic iTunes library or rolling through the suggested videos on YouTube only to continually adjust the speakers because the next song is too loud or quiet. Ok, perhaps not always, but this is a regular occurrence. The LUFS metering system ensures that all music plays back at a consistent level. This creates an enjoyable experience for the listener, and let’s face it: the audience is always the most important person to cater to.
Different Measurement Units
It’s important to recognize that there’s a significant difference between the units of measurement used by VU or PPM meters (dBVU and dBFS, respectively—the “FS” stands for “Full Scale”) and those used by loudness meters (LUFS). In addition, loudness meters such as the Waves WLM Plus Loudness Meter plugin provide numerical readouts instead of abstract needle swinging or segment lighting: either you hit the target, or you don’t; no interpretation is needed.
LUFS Scale
The Broadcast television industry uses the LUFS scale extensively. Additionally, government standards mandate consistent volumes between channels and when a channel switches from program material to commercials. Video games and online delivery systems also use the scale. Some game companies specify that a music track mix must fall within defined LUFS levels. This is because they can better predict how it will balance with the other game sounds.
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