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Audio Levels 101 – All You Need Is LUFS

 

What the heck is dBFS, true peak, RMS, integrated loudness and LUFS? Why do I need to know these strange appellations?

As a professional sound designer you will eventually stumble across technical terms referring to audio levels and loudness. A customer might tell you: “we need a track with an integrated loudness of -23 LUFS, a dynamic range of 15 LU and a true peak of max -1 dBTP”. Even if you’ve been producing audio for a few years you might be thinking: “huuuuuh…?”.

By now you’ve probably heard about the loudness war, and we all know what it sounds like when audio “peaks”, “clips” or hits the “red zone”. So far so good. But in order to make your audio sound pleasant and meet industry requirements, you need to know a thing or two about setting your audio levels right, and how to approach loudness when creating audio. Here’s a fun video explaining what the loudness war does to audio in practice:

 

All you need is LUFS?

Audio produced for a specific medium should always sound pleasant, dynamic and more or less “equal” in terms of perceived loudness. Unfortunately your basic DAW meters aren’t giving you the whole truth about your audio. These meters display audio in dBFS (decibels relative to full scale) and only tell you whether your audio signal is clipping or not. To judge actual loudness, our ears respond to average levels, not peak levels.

The new standard for measuring audio loudness is LUFS (loudness units relative to full scale). It was developed to enable normalization of audio levels, and matches how our ears actually perceive sound. LUFS meters will also tell you the integrated loudness of your audio, which is similar to RMS (root mean square) but more truthful in terms of our hearing. RMS tells you the the average power of the signal, but LUFS integrated loudness is more accurate in terms of our perception of loudness.

The integrated loudness can be understood as the “overall” level of your audio. It’s also good to keep in mind that different meters serve different purposes. You will still need to use your dBFS meters to make sure your signals aren’t clipping.

 

How loud is loud enough?

Your audio should always be loud enough. What this means varies depending on how noisy the environment is (imagine in-flight entertainment), what device you are using (e.g. an iPad with headphones on the bus), and what the intended end medium is (e.g. your home TV set or a movie theatre). Especially in broadcast media (TV, radio, etc.) there are standards that require the audio to have a strictly defined integrated loudness level, most commonly -23 LUFS. This is to ensure healthy sounding audio and to avoid those annoying dynamic bumps between commercials and programme audio.

A lengthy, more technical (but fun!) explanation of these things can be found here:

 

Summing it up

When mixing to LUFS values, your mixes will sound more consistent. The dBFS scale only measures the electrical level of the sound. If you try mixing to a level of e.g. -15dBFS, your results will likely hit different LUFS levels every time and might end up sounding different.

If you don’t yet own a LUFS meter, remember to pay attention to your RMS readings. If your dBFS peak levels go higher than -3dB, you might be in trouble. As a rule of thumb, RMS readings around -18dBFS and -14dBFS should be OK.

A special treat – your own LUFS meter!

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Wow! All of the above might have been a lot to take in. As a special treat, Audiodraft and MeterPlugs are offering a unique chance to get a nice loudness meter at a discount until March 9 2016. You also have the chance to win this plugin for free before March 9 by participating in this Audiodraft Challenge.

 

 

 

 

If you’d like to learn more about these things, here are a number of very useful links we recommend checking out:
http://www.tcelectronic.com/loudness/loudness-explained/
http://www.tcelectronic.com/loudness/broadcast-standards/
http://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP202.pdf

 

A Short Glossary

dBFS – Decibels relative to Full Scale. This scale is used for amplitude levels in digital systems (e.g. your DAW). 0 dB FS is the maximum level. The scale refers to the amplitude of a signal compared with the maximum which a device can handle before clipping occurs.

LUFS – Loudness units relative to Full Scale. This is a loudness standard designed to enable normalization of audio levels. Loudness Units (or LU) is an additional unit. It describes loudness without direct absolute reference and therefore describes loudness level differences. For instance, the difference between -23 LUFS and -18 LUFS is 5 LU.

dBTP – dB True Peak. The scale is actually dBFS, but measured with a true peak meter. dBTP refers to the peak amplitude of a signal compared with the maximum which a device can handle before clipping occurs. In digital systems, 0 dBTP would equal the highest level (number) the processor is capable of representing. Measured values are always negative or zero, since they are less than or equal to full-scale.

True Peak – A maximum absolute level of the signal waveform. It measures the peak levels of samples and intersample peaks.

RMS – Root mean square. The average power of your audio signal, and close to what your ears perceive as the loudness of your audio.

Loudness range – Dynamics of your audio, or difference between the average “soft” and average “hard” parts (excluding extremes). Similar to RMS, but based on the LUFS scale which is optimized for human perception.

 

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