Home Mastering Headstart – Lesson #2
Loudness, levels and how to measure them
You may have picked up from the last lesson that I’m going through all the main mastering processes in the reverse order to the one you use them in!
That’s because everything that comes earlier in the chain feeds into what comes later – the limiter is the last processor in the chain, for example, but I can’t explain how to use EQ or compression without discussing limiting first.
Last of all though, even after the limiter, comes the metering. Metering many not seem as interesting initially as EQ or compression, but it is an essential part of mastering, especially when you’re training your ears.
Of course it’s possible to master without metering when you’re experienced, but I think I’d go as far as to say it’s actually impossible to learn mastering without metering.
I’m talking about level metering here – I recommend you use a frequency analyser too, but I’ll cover that in Lesson #5. The type of meter I’m going to recommend to you is a modern Loudness Unit (LU) meter. Loudness units relative to full-scale, or LUFS, are an internationally agreed standard developed to help regulate broadcast levels.
What an LUFS Meter tells you
An LUFS meter wraps several valuable measurements up in one handy package. They are:
True Peak Level
You’re probably already familiar with the idea of the peak level – it measures the instantaneous digital level of the musical signal. It’s important to not let this hit zero, to avoid “clipping” distortion, and when recording or mixing at 24-bit I usually aim for a reading of -6dB peak at most – often much lower. When mastering, the peak level often pushes up to near zero but I still recommend you keep it a little below maximum – more on this in the next lesson about limiting.
One important point to notice about the peak level is that it tells us almost nothing about how “loud” things are – some very dynamic or “peaky” sounds like piano, percussion or voice can have a high peak level but sound quite quiet, whereas other “smoother” or less dynamic sounds like flute, organ or keyboard strings will sound much louder even though their peak level is lower.
So why are they called “true” peaks ? Because with very loud signals it’s possible to get peak levels which will over-shoot digital zero when the signal is played back or processed in some ways – for example sample rate conversion or mp3 encoding. The True Peak (TP) anticipates this problem and warns you in advance, so you can avoid problems later.
Three types of loudness
Loudness can be measured in three ways. Firstly, you can measure the overall loudness of an audio file or stream – this is known as the integrated loudness. It’s a handy way to summarise the loudness of a song or album, but it won’t warn you of any short extreme values.
Next is the short-term loudness, which I find most useful. It smooths the loudness values over a 3-secod window, giving a clearer idea of how our ears will perceive the loudness in realtime.
Finally you can measure the momentary loudness – this value varies very quickly and personally I don’t find it especially helpful in mastering.
LUFS versus RMS
You may already be used to judging loudness using an RMS meter. RMS stands for “root mean squared” and is a useful approximate guide to loudness – sounds with a consistently high RMS will sound louder than sounds with a low RMS. When I first started mastering, I used an analogue “VU meter” to judge loudness – VU gives a similar reading to the RMS level.
LUFS measurements are more sophisticated though, and try reflect the sensitivity of our ears to different frequency ranges, which I find makes them more helpful for assessing loudness in mastering.
You can see a video demonstrating how LUFS and RMS work here.
Using an LUFS Meter in Mastering – don’t aim for targets !
Some people suggest using integrated LUFS values to decide how loud to master your music. DON’T !
It’s easy to see why this approach won’t work if you think about a specific example – a gentle acoustic ballad versus a pounding heavy rock track, for example. It doesn’t make any sense for such different types of song to be the same loudness from a musical perspective, so why would we expect aiming for the same numerical target to sound right ?
Instead, I recommend you keep the loudest moments for your music to a consistent volume, and balance everything else compared to this. You can read about this method in detail in here:
How loud ? The simple solution to optimizing playback volume online – and everywhere else
So, how loud ?
My suggestion is to use other music you like the sound of as a reference – this is something I’ll come back to regularly. Here’s what I recommend.
Choose a few songs in a similar style to the ones you want to master. Don’t go crazy – bear in mind that if you choose big-name productions, you’ll be setting the quality bar high – although there’s nothing necessarily wrong with that ! You may not get quite where you want to the first few times you try, but you’ll learn a huge amount in the process.
Now:
- Load your “reference songs” into your DAW and play them back through the loudness meter
- Take note of the short-term LUFS levels at the loudest moments
- If necessary, reduce the levels of the songs so the loudest sections read around -10 LUFS (short-term)
- Adjust your monitoring level so that this is as loud as you would comfortably listen to for long periods of time
- Make a note of this monitoring level – it should be one of your reference points, from now on – your “mastering monitoring level”
- Turn the output down by 12 dB – this will give you a useful alternative quieter perspective
- From now on, only ever use one of these two monitoring levels when mastering
(This will help you learn how your music “should” sound, giving you and invaluable reference-point) - Now master your own songs to sound as good as possible in comparison to your reference songs!
Of course, I haven’t told you how to use all the other processing to do that yet – that comes in later lessons 
But this sequence ensures you get a fair comparison against the music you’re using as a benchmark, without tempting you to push the average level so hard that you damage it. The LUFS level tells you how much to turn the level down by, so you can match the loudness without pushing higher than -10 LUFS too often.
You can go for a measurement above -10 LUFS, but I think consistently pushing the level any higher goes beyond the “loudness sweet spot” and starts to do more harm than good. If the song you chose to compare against needed turning down by 2dB or more, then yours has the real potential to sound even better, dynamically – click this link to find out why:
How to make your music pop – online, and everywhere else
Loudness for streaming
You probably know by now that for all the current obsession with loudness, online streaming services like YouTube, Spotify and TIDAL are reducing the playback level of very loud songs to prevent users being “blasted” by sudden changes in level.
Which means that no matter how loud you make you master, it won’t necessarily sound loud online !
The good news is that the guidelines above will work extremely well for online loudness, as well as sounding great. And to help you check this for yourself, I’ve created a free website with MeterPlugs. It’s called Loudness Penalty, and it’ll tell you quickly and easily – and for free – exactly how the loudness of your masters will be affected online. You can even Preview the final loudness levels and compare them directly against reference tracks on your favourite streaming service.
Check out the Loudness Penalty site here:
On the way
If you follow the guidelines above you’ll find your music will sound loud and punchy in almost any environment, have a great balance of dynamics and plenty of room for emotional impact. And of course, if you prefer to choose a lower LUFS reference-point then your music can have even wider dynamics. As you learn how the LUFS values change depending on the EQ and compression you choose, you’ll also start to gain an instinct for level and loudness – and hear how it interacts with EQ.
And you’ll be well on the way to getting great results mastering your own music…
P.S.
Did you get here via a link from a friend, or Twitter? This lesson is part two of a 7-part free email course to give you a head start with home mastering. I give you quick, useful guidelines from a professional perspective to help you get started today, without damaging all the hard work you’ve already done. Learn more about it and sign up here.