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What are LUFS and what are they for?

What are LUFS?

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Have you ever been listening to music when suddenly the next song starts and it's so loud that you have to turn down the volume? Or the other way around: you have to raise the volume a lot so that the new song sounds as loud as the old one. This happens when the music is not mastered at a constant volume (whether on an album, on different streaming sites, etc.) and therefore the perceived volume becomes noticeably unbalanced during playback.

To avoid exactly these problems, the LUFS were developed, a standard for volume measurements. This allows each platform to specify LUTS so that the Mastering-engineers know what volume to master the song to.

In this article we explain what you need to know about LUFS, the new way of measuring levels in audio, and what it means to use it in music production.

What are LUFS?

LUFS is a new method for measuring audio levels and loudness. It takes into account human hearing patterns that correlate better with reality than other measurement methods, such as dB.

Example of volume measurement
Example of volume measurement with iZotope Insights (Source of image: iZotope.com)

The acronym stands for Loudness Units Full Scale or Loudness Units Relative to Full Scale.

What was the LUFS invented for?

There were 2 main objectives in the invention of LUFs:

  1. The other and more important goal is to standardize the volume of television and radio broadcasts, which ultimately affects the world of music production and streaming, as mastering engineers now have to master at different volumes depending on the platform.
  2. The other and more important goal is to, standardise the volume of television and radio broadcastsThis ultimately affects the world of music production and streaming, as mastering engineers now have to master at different volumes depending on the platform.

Loudness in the last century - "The Loudness War

The war for volume on streaming platforms like Spotify, Apple Music or YouTube is over or about to end.

For years, mastering engineers have fought over the loudest tracks. The assumption has been that a song is perceived as "better" or "hornier" if it is louder.

That's good news! Because mastering is no longer just about who masters the loudest, but who masters the best.

Sound engineers in the world of radio and television have been trying for some time, through various initiatives, to avoid abrupt volume jumps between programmes and commercials, as such jumps interfere with the enjoyment of the user, who then changes the channel during commercial breaks because he is startled.

These concepts were eventually adopted by other digital music streaming platforms in a similar way, such as Spotify, Tidal or Apple Music.

The purpose of these regulations is to standardise or normalise the average loudness value rather than the peak values that have been used so far.

That is, instead of requiring that the peaks reach a certain level without taking into account that the average volume might be too high, we now require that the average level of the volume corresponds to a certain standard.

The goal is to achieve a average for the entire program.

In this way, the aim is to ensure that the volume, which is closely related to the average level, of a programme and of the commercial breaks is uniform.

LUFS: Practical implementation in music production

The realisation has two parts, one in the production and the other in the reproduction by the final medium.

  • On the production side, it's a matter of adjusting the average level to a value determined by the medium being processed (e.g. -14 dB when mastering for Spotify).
  • On the other hand, the playback side has a system built in that evaluates the level of the music. As soon as a song has a lower or higher LUFS value than what the platform specifies, the volume of the song is raised or lowered (by a limiter, among other things).

That's why it's extremely important to master too loudly rather than too softly, because you never know how your song will sound when Spotify raises the volume with a limiter. Your mix can change, and suddenly the bass or vocals can be too loud.

YouLean is a very good and free VST plugin to set the volume
YouLean is a very good and free VST Pluginto set the loudness

But when Spotify reduces the volume, you can be sure that your mix remains the same, because here only a "fader" reduces the volume without compressing the song.

If the nominal level is e.g. -14 dB (Yes, LUFs are also measured in dB!) and the file has a level of 10 dB when analysed, i.e. 4 dB above, this information is stored and when the file is played, the level is reduced so that it corresponds to the default level suggested by the platform.

Considering that most digital streaming platforms have this system built in, it no longer makes sense to look for the maximum possible volume, as the platforms bring the volume to the level they set and any deviation is corrected when the file is played.

So it's enough to make sure that the song at least meets the requirements of the platform, but doesn't fall below.

If mastering is done with the aim of achieving a high volume level, it only reduces our chances of getting good audio quality, as you have to distort the peaks, and the best possible representation of our music, as the platforms will automatically adjust the level at the end.

Instead, good mastering engineers these days can concentrate on just making the song sound good.

The paradigm shift levels the playing field between super productions and more modest productions, avoiding over-compression that leads to a loss of sound quality in transients, detail and clarity.

Waves WLM Meter is my favourite plugin to measure the LUFs.
Waves WLM Meter is my favourite plugin to measure the LUFs.

LUFs: The new measurement standard

For EBU research, a new way of measuring average level was needed to get closer to the perception of loudness. The resulting measure is called LUFS (Loudness Units Relative to Full Scale).

The measurement has a frequency weighting component and an integration over time to match the way our hearing works. The integration can be short, 400 ms, short 4 seconds, or integrated, which includes the period from the start of playback to the pause.

Accordingly, different values are obtained during the measurement: Short Term (4 sec), Momentary (400msec) and Integrated (over the entire length of the song).

The average level we should aim for is given in LUFS and the optimal level depends on the platform we have to work with. The table shows some reference values for the LUFS level that the final master should aim for.

PlatformRecommended LUFs in dB
Spotify-14
Youtube-13
Apple Music-16
Tidal-14
Amazon Music-14

Although all these platforms aim for a different level, unfortunately the music aggregators on them usually only allow you to upload a digital file, so you have to cope with a compromise.

In such a case the compromise should be close to -14 LUFS, which is an intermediate value between the platforms and allows us not to aim for too high a level during mastering and thus achieve a result with more dynamics.

LUFS: How do I ensure good levels?

Even though the new standard was developed to avoid an excess of compression/limiting, the real levels are also measured here. We need to measure the peaks with a real peak meter that calculates what happens when we switch the signal from digital to analogue.

The purpose of this measurement is to avoid the distortion that occurs with some converters and especially when creating a file with data compression such as mp3 or AAC. This type of file increases the final level of the master and can therefore cause distortion.

The standard suggests that the peak values are - 1 dBTP/-0.5dBTP, True Peak. This way you are always on the safe side and avoid distortion. Meters that have the LUFS standard usually include the true peak measurement.

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