A level meter is a display that shows the size of an audio signal over time. There is one on every DAW channel and on the master output, letting you check with your eyes and with numbers whether the recording level is too high, whether the left-right balance is skewed, and how far the momentary peaks reached.
Peak meters
A peak meter catches the highest instantaneous level and helps prevent clipping. A peak hold display keeps the maximum value during playback for a set time or until you reset it, which makes it easier to catch a loud sound that occurred for only a moment.
RMS and loudness meters
RMS shows the average energy over a short window and is a better guide to perceived loudness than peak values. A loudness meter showing LUFS also takes into account how our ears respond to different frequencies, and is used to check the perceived level of a whole song or programme.
Where to check
Check the input channel while recording, each track and bus while mixing, and the final output meter before exporting. If the level changes a lot before and after a plugin, putting a meter at that point too helps you pinpoint where the signal became excessive.
Trace the cause when it goes red
When the clip indicator lights, check not only the fader but also the input gain and the output of the plugins before it. Even if the DAW works internally in floating point, the recording input, the final output, and fixed-point files all have a ceiling, so it matters to look at the whole signal path.
Do not decide by numbers alone
Peak, RMS, and LUFS look at different properties, and no single number can tell you the quality of the sound. Check noise, distortion, and balance with your ears, and use meters as support. With the tool for adjusting the loudness of your audio you can see LUFS and estimated True Peak for yourself.
