3.6 Level Up: Metering RMS and Peak
Audio levels or audio intensity is measured by units called decibels. I also sometimes called them DBs. Decibels are measured from 0db being the loudest, and -infinity being the quietest. So - 3db is louder than -6db and so on. Now you might see that Ableton has a setting in which you can turn a track up above 0db but at the end of the day, the loudest that digital audio can be exported is 0db. Don't worry we will go over this concept thoroughly in the section on limiting and exporting.
When mixing in Ableton Live and when you have the track volume slider expanded in session view, you can see both little indicators just to the left of the volume slider showing you both the peak level and the volume slider setting in decibels.
Now I know we already learned that, but you may have also noticed that when watching the tracks when they play, that there are colored meters that light up both bright green and dull green. These different colors visually represent to 2 very useful measurements of loudness. One is called peak level (the dark green) and the other is called Root Mean Square or RMS level (the bright green). The darker green shows you the Peak level or the loudest peak of the track's output, as in the absolute loudest point the audio is reaching. The bright green is showing the RMS level which is the average loudness of the track. Watching and using these levels to help you make decisions as you mix is called "metering" and both peak and rms levels are very important indicators that you will use as you get better at mixing.
Let's begin with peak level or the dull green color in our volume meter. Peak level is showing you the loudest spike in the audio waveform. This meter is very useful as it helps you to ensure that you don't go passed 0db. What happens when you pass 0db? Well something called digital clipping occurs. Commonly digital clipping causes very undesirable results akin to scratchy glitchy piercing sounds. Ableton has a built in feature to show when you are clipping the output of the master bus. Whenever 0db is breached by the peak meter on the master track output, it will turn red, indicating that you are out of "headroom" or, the loudest your audio can get before it distorts. Obviously you'll want to avoid digital clipping and keeping your audio safely below 0db is obviously a good practice to adopt. But not all clipping is bad, in fact clipping is also something that can sound really good, thats why there is an entire section of this course dedicated to the many forms of saturation available to you which is essentially different styles of clipping. But having your audio peak above 0db on your master bus is DEFINITELY NOT the kind of digital clipping you want. Thats why the peak meter is important. It helps you keep your audio within the optimal range to remain free of digital clipping. There are other reasons peak level is important but we will go over those in another lesson.
Now moving onto RMS levels or the bright green color on your volume meter. To avoid nerdy-ness, it will suffice to say that RMS is a measurement of audio that displays the average loudness of a track. This meter is showing you something close to how loud the audio is perceived by the human ear. Now you might be thinking, why would i need a meter to show me how loud something sounds!? I can just listen and tell you that! Well lets break this down a bit. The RMS meter can be useful in helping you determine whether or not your track would benefit from compression or saturation, whether or not an audio effect is an improvement or a step backwards, it can help you set the level of a reference track that you are comparing your mix to and so on. Now if I've lost you at all, don't worry, all these concepts will be explained in excruciating detail in following videos.
Now if up until this point you have looked at track meters and just thought of them as nice little visuals while you mix, well all i can say is that you're going to get a giant upgrade to your skills as we are going to be talking about and using these meters throughout the rest of the course. Understanding and utilizing peak and rms meters is absolutely crucial to good mixing practices.