What is loudness or LUFS?

Loudness or LUFS describes how loud we perceive an audio signal to be. But caution please, things are a bit complicated.

What is loudness?

Loudness is primarily a matter of perception. Whether we perceive sounds as loud or soft depends on many factors. The so-called power level, which is expressed in decibels (dB), is only one of several variables.

The video demonstrates how loudness affects sound quality.

The frequency of the sound plays an important role as well. People perceive frequencies around 3,000 hertz as particularly loud; loud bass frequencies do not seem nearly as loud to people, but they drive the level up.

Therefore, in the long run, both the peak level and the average level have proven to be unsuitable units of measurement to describe loudness.

Unlike level measurement, the measurement of LUFS takes into account both frequency and signal intensity. Therefore, the measured loudness in LUFS corresponds more closely to the actual human impression of loudness.

Den Youlean Loudness Meter setzen auch professionelle Tonstudios ein, um die Lautheit zu messen. Links lassen sich die verschiedenen LUFS-Werte ablesen. Rechts wird die Lautheit im Zeitverlauf angezeigt.
The Youlean Loudness Meter is used by professional sound studios to measure loudness. On the left, the various LUFS values can be found. On the right, the loudness is displayed over time.

What does LUFS mean?

LUFS stands for Loudness Units relative to Full Scale. This is a key figure to compare the loudness of audio signals in a standardised way.

What is a LU (Loudness Unit)?

LU means Loudness Unit and refers to the units of which LUFS are composed. One LU describes the difference between cut and gain during leveling. 1 LU corresponds to 1 dB.

What types of LUFS?

To determine the LUFS, time must be included in the calculation. Different loudness times can be determined in LUFS.

  • LUFS M (momentary max) stands for the momentary loudness in the time window of 400 milliseconds.
  • LUFS S (short term max) stands for the short-term averaged loudness in a time window of three seconds.
  • LUFS integrated refers to the loudness of an entire programme section. This means a commercial from beginning to end, a piece of music or even a complete CD or side of a record. Measurements are taken from the beginning of playback. Therefore, the value levels off with increasing playback time. Streaming portals and uebervinyl.de use this value to compare the loudness of audio signals.

During the measurement, an algorithm ensures that unwanted signals – for example the hum of an air conditioner or noises from the audience – are not taken into account.

What do we need LUFS for?

The LUFS unit helps sound engineers compare different audio signals and adapt them to different playback situations. It also ensures that listeners of streaming services perceive approximately the same loudness for music pieces by different artists from different albums. For TV stations, too, LUFS restrictions for commercials are intended to help curb the competition for particularly high attention through loudness for commercials.

The new parameter LUFS had become necessary because the previously valid level limit (in German television, for example, +6dBu) was oriented exclusively to the peak level. However, an equal level does not mean an equal loudness perception for the human ear. Through the massive use of compressors and limiters, the advertising industry had produced commercials louder and louder without exceeding the peak level.

In the meantime, there is a recommendation by the European Broadcasting Union (EBU), an association of European broadcasters, which recommends a maximum value of -23 LUFS for commercials on radio or TV.

Streaming services have also introduced upper limits for the loudness of music files. These are

  • on Youtube -14 LUFS
  • on Spotify -14 LUFS
  • on Itunes -16 LUFS

Itunes demands a somewhat lower average loudness than other streaming services. If a song is delivered too loudly, the streaming services play it correspondingly quieter. This is called a loudness penalty – a punishment for excessive loudness. You can find more standards and norms here.

How does uebervinyl.de measure LUFS?

After digitising the music signals as uncompressed WAV files, the complete album pages are layered through the Youlean Loudness Meter. This plug-in is also used by professional sound studios to determine the value for LUFS integrated.

How should LUFS values be interpreted?

LUFS values initially say nothing about whether a piece of music sounds good or bad. For the sound assessment of remastered vinyl records, however, the LUFS value is at least an indication of whether the loudness was maximised during remastering or whether the sound engineers preserved the dynamics of the original. If the re-release has a lower LUFS value than the original, the dynamics were rather reduced in favour of loudness.

Wellenform-Diagramm für Sympathy For The Devil - Rolling Stones
Waveform Diagram for Sympathy For The Devil – Rolling Stones

In some cases, the loudness of certain pieces of music is reflected in the waveform diagrams. Sympathy For The Devil by the Rolling Stones in the Japanese pressing of the album Beggars Banquet (above) has a LUFS value of -16.1 integrated. The comparative pressing from 2018 (below), on the other hand, is -5.5 LUFS quieter on average at -22.6 LUFS – which corresponds to -5.5 dB.

LUFS-Messung für Sympathy For The Devil von den Rolling Stones in der japanischen Pressung von 1988.
LUFS measurement for Sympathy For The Devil by the Rolling Stones in the 1988 Japanese pressing.
LUFS-Messung für Sympathy For The Devil von den Rolling Stones in der Pressung von 2018.
LUFS measurement for Sympathy For The Devil by The Rolling Stones in the 2018 pressing.

But there are also original recordings that have already been mixed very loudly. If the loudness is already present on the master tape in many cases is a deliberate artistic decision. In this case, even the best mastering engineer cannot produce a highly dynamic remastering from a very loud master.

Wellenform-Diagramm für My Sharona - The Knack
Waveform diagram for My Sharona – The Knack
My Sharona von The Knack in der Loudness-Messung mit dem Youlean Loudness Meter
The 1979 version of My Sharona by The Knack in the loudness measurement with the Youlean Loudness Meter
My Sharona von The Knack auf Mobile Fidelity Sound Lab in der Loudness-Messung mit dem Youlean Loudness Meter
My Sharona by The Knack on Mobile Fidelity Sound Lab measuring loudness with the Youlean Loudness Meter

My Sharona by The Knack, released on the album Get The Knack, was optimised for loudness by producer Mike Chapman during the mix and later during the lacquer cut in 1978, reaching a remarkable -16.5 LUFS (top left). When Mobile Fidelity Sound Lab started remastering, the stereo mix was already quite loud (above right). Without further compression and limiting the lacquer cut, the loudness still remained at -19.8 LUFS.

Sometimes, however, the source master is anything but loud. In this case, it can make sense to raise the volume moderately during remastering.

Wellenform-Diagramm für Welcome To The Working Week von Elvis Costello
Waveform Diagram for Welcome To The Working Week by Elvis Costello

My Aim Is True, the debut album by Elvis Costello, is such a case. For the lacquer cut in 1977 (diagram above, upper wave), the loudness was raised by compressor/limiter to -16.8 LUFS (bottom left). For the remaster by Mobile Fidelity Sound Lab (in the waveform diagram below), on the other hand, no further compression was applied and simply the original master was cut without dynamic processing (below). The result is very quiet with -28.0 LUFS (bottom right) and also highly dynamic, as the waveform diagram (above) indicates. But here the running noises of the record as well as any crackles disturb the listening pleasure, as they partially drown out the music signal.

Loudness-Messung für Welcome To The Working Week von Elvis Costello in der Pressung von 1977
Loudness measurement for Welcome To The Working Week by Elvis Costello in the 1977 pressing

Loudness-Messung für Welcome To The Working Week von Elvis Costello in der Pressung von Mobile Fidelity Sound Lab
Loudness measurement for Welcome To The Working Week by Elvis Costello in the Mobile Fidelity Sound Lab pressing

The appropriate loudness also differs depending on the musical genre. For classical music or acoustic jazz, the focus is on dynamics. High LUFS amounts above -20 are more likely to fit here. Heavy metal, punk or even electronic music, on the other hand, can still sound appropriate with less than -15 LUFS.