LUFS, dBFS, R128, dBTP, ITU BS 1770, ATSC A/85, PLR & PSR…
There are now so many ways to measure your music these days, it’s not surprising that one of the most common questions I get asked these days is
What do all these acronyms mean ?
In particular, people want to know about the new “ITU-based” loudness meters, which use mysterious new “Loudness Units” – LU for short, or LUFS to be more technical. Especially as mainstream software like Cubase 7, Logic and Ozone Insight begin adding support for them.
You know they’re important, you know that meters using the new system are appearing in more and more places – but how do you know what they mean ?
Well the good news is, it’s not as complicated as it seems. There’s a pretty simple relationship between the new LUFS measurements and older loudness measurements we’re used to, like RMS or VU levels.
The video above demonstrates all of this, as clearly and simply as I could make it – as well as an important complication with RMS levels that everyone needs to know about.
You can download the “pink noise” test file I use in the video to try this for yourself here.
I hope you find the video helpful, and let me know if you have any questions !
Appendix: Get your RMS right !
I mention in the video that some DAWs and meters use the wrong method to measure RMS for music, and so many people have asked me about this I thought I’d add some more detail.
RMS can be calibrated using either a full-scale square wave, or a sine wave. The correct way to do this for a music signal, as defined by AES Standard AES17-1998, is to use a sine wave peaking at 0dBFS – for more details, click here.
If a meter is calibrated using the wrong standard, the RMS level will under-read by 3dB, and you’ll be tempted to mix or master everything too loud.
Here is an (incomplete) list of DAWs and meters this has been tested in:
Logic 9 and Logic X
(Take care – the multimeter displays peak RMS by default, which muddies the water even further…)
Waves PAZ – 4dB off (?!)
T-RackS (All versions)
(Actually by default it’s wrong but this can be corrected using the “RMS +3dB” preference)
Reaper is about right, but the time constant needs to be correctly set to 300ms
Ableton (Version 9.5)
Test for yourself
Simply download the pink noise file here and try it in your own DAW or meter – the RMS level should read very close to -11.5 dBFS. If it doesn’t, something is wrong.
And, please feel free to report the results of your own tests in the comments.