Levels Demystified – DAW Metering Explained (Part 5)

A POP Quiz

To kick things off I have a question for you.  What exactly does the built-in meter in your DAW tell you?

  1. How loud your signal is?
  2. How great your mix is?
  3. How good looking you are?

Now I know most will go back and forth between Answers 1 and 3, but would it surprise you to learn the answer is actually ‘None of the above!’  That’s right.  Your DAW meter does not tell you how great your mix is, how great you look, and though this may come as a shock to many it does not tell you how loud a signal is.

What?  I hear you scream.  This is heresy!  Burn him at the stake!  Well before I have my last meal and kiss my children goodbye please allow me to explain myself.

Your DAW’s Built In Meters

The meters built into most DAW channel strips are ‘Peak’ meters.  And what exactly is a Peak Meter I hear you ask?  Well a Peak meter is a fast meter designed to measure the instantaneous and momentary sample value of a signal.  Simply put this means a Peak meter will let you know if a signal is about to go into the ‘red’ and clip.  And clipping is bad…very bad!  Say it with me, ‘C-l-i-p-p-i-n-g-I-s-B-a-d!!!’*

Peak meters measure signals in dBFS with a reading of ‘0’ at the very top of the meter.  To measure the loudness of a signal we cannot rely on your DAW’s built-in Peak meters.  Instead we need the trusty services of a RMS Meter (which stands for ‘Root Mean Square’ by the way.)  Unlike Peak meters, RMS meters are designed to measure the ‘average volume’ of a signal – giving you a truer picture of how loud a signal actually is.  It can be helpful to think of Peak & RMS meters ITB like this:

  • Peak Meters – Help you avoid clipping
  • RMS Meters – Meausres the actual loudness of a signal

Let’s take a quick look at an example.

Peak VS. RMS Levels

The picture to the right shows the Input and Output Meter of iZotope’s Ozone 5.  The meter on the left is the Input meter.  Notice that it shows the signal ‘peaking’ at -0.4 and -0.3 dBFS for the left and right channels (which is the same information your DAW meter would give you).  It also shows that the average loudness of the signal (or its RMS value) is in fact -22dBFS!

Now if you relied solely on your DAW’s meters when recording this signal you might conclude your levels were too hot and turn them down.  But by looking at the RMS level we can see that all is well and good and your level is actually coming in at around the sweet spot of -18dBFS RMS**.

The Take Away

So what can we take away from this?  Your built in DAW meters are great for measuring peaks and keeping you out of the badlands of digital clipping.  But if you want to know the ‘loudness’ of your signal you’ll need to reach for a RMS meter or one of its soon to be introduced substitutes!

Stay tuned!!!

 

*  Most DAWs today operate with a 32-bit Floating Point architecture.  This basically means that signals no longer clip at 0dBFS due to some technical wizardry the DAW does on your behalf behind the scenes.  The result?  Unlimited headroom – well at least in theory.  The reality is most emulation type plugins still have a sweet spot of around -18dBFS so pushing them too far beyond this point may make you feel like a rebel but your sound may suffer.  As always if you push it hard and it’s sounds good, then it is good!  But if it doesn’t you may want to ease the load on your plugins.  (Check out this video for a quick explanation of 32-Bit Floating Point.)

** As a quick aside can you now see why -18dBFS RMS is not the same as -18dBFS?  (-18dBFS is actually short hand for -18dBFS Peak.)  In fact a reading of -18dBFS RMS is normally much lower than a reading of -18dBFS Peak.   A signal that reads -18dBFS on an RMS meter may peak anywhere up to 0dBFS (or maybe even higher) like in the Ozone 5 example above.

So when recording your DAW meter may be peaking at -10dBFS but your RMS level may actually be hovering around the -18dBFS in the sweet spot range.  Make sense?

Levels Demystified Part 6

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