What is loudness? Using RMS meters (+ a free RMS meter to download!)

Michael TerrenAbleton Super Powers, Free Downloads, Max for Live, noisemakerLeave a Comment

Download the RMS Meter device as part of Michael Terren’s suite of Max for Live Devices

There is a golden rule for mixing with plugins, and you could summarise it by saying “know your loudness.” Keeping loudness levels the same between plugins is essential to making crucial and objective decisions when mixing. Why? Because our ears aren’t very clever—they think that louder is always better. If you slam a compressor’s output gain by 8dB or so, of course you’ll think it sounds better, but if you turned the volume down to the same loudness pre-compressor, you might find that you’ve sucked out everything that sounded good about that sound!

You might notice I’ve used the term loudness a lot here, and not volume. Loudness is not the same as volume or amplitude. Loudness has to do with perception—it relates to how loud we perceive a sound to be. Volume and amplitude are empirical because they can be measured by scientific tools, but these tools can’t tell us how loud we think a sound is, that’s the stuff our brains and our ears process.

Why make the distinction? Because in Ableton Live, the meters represent the amplitude of a sound, not their loudness. They are what’s known as peak meters, because they’re designed at showing you the amplitude of the very loudest sounds. If you’re trying to compress a sound’s dynamic range, while keeping its apparent loudness the same as it was before, your peak meters could look a little different.

Keeping loudness the same between plugins takes practice and time, but there’s scientific evidence which suggests that we have a preference for sounds that are 0.1dB louder than a sound that is otherwise identical. There’s no substitute for closing your eyes, switching between a sound with and without some effect (also known as A/B’ing) and making a decision—as objective as possible—about whether that effect is really making things sound better.

A lot of classic analog mixing desks use what’s known as VU meters. These are the meters with needles that dance left to right, and they are one way of giving a basic idea for the loudness of a sound. VU meters still exist, but in the digital realm we tend to use RMS meters. RMS (root mean squared) is a mathematical process which provides an average loudness over time (as opposed to peak amplitude). They’re useful for getting a basic idea of how loud things are. Ableton Live doesn’t have an RMS meter, and while Max has one (called levelmeter~) I’ve found that it isn’t as accurate as it should be. Thus, I’ve made my own RMS meter.

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The green arrow indicates the RMS level, which is also reflected by the dB reading underneath the meter. The red meter is the standard Ableton peak amplitude meter.

Again, I must stress that this isn’t a replacement for training up your ability to hear small differences in loudness—it’s only there to give you a ballpark figure to compare some sounds. It might be helpful too when mastering, to give you an idea of how loud other tracks are in comparison to your own. Use it wisely!

Download the RMS Meter device as part of Michael Terren’s suite of Max for Live Devices
Michael TerrenWhat is loudness? Using RMS meters (+ a free RMS meter to download!)

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