There are two main types of meters in audio, peak and rms (root mean square or average). Each of these have their own benefits, but on the simplest level they are used to show the user the level of audio signals as they flow through certain parts of a console, recorder or system.
A peak meter shows the peak of an audio signals waveform. If there is a large spike the meter will max out and if the signal gets soft the meter gets low as well. Peak meters are very useful for helping users to avoid distortion caused form clips or overages of the peak signal. Peak meters are very common in DAWs in mixers, on plug-ins and on audio interfaces. Peak meters in analog mixers are usually done with LEDs in order to accurately reflect the quick changes in analog levels unlike the slower response of VU meters.
RMS or Average Meter
VU meters are the most commonly found average meters. Instead of displaying every peak and soft portion of an ausio signal, VU meters show the average signal with a relatively slow speed of 300 milliseconds (3/10s of a second). This may not seem useful for avoiding clipping, but it has benefits that ‘hit close to home’. Our human ears hear in averages, not peaks, with a similar response time to VU meters. This all ties in with perceived loudness and the miracle of compression. As the average level of a signal increases, our ears perceive the sound to be louder even if the signal’s peak does not change. VU meters help us to see what our ears are hearing. RMS and average meters are not only found in VU meters. They are often seen along side peak meters on analyzers and mastering plug-ins the software world.
Trust Your Meters
Both peak and average meters can be powerful tools when working with audio. Trust your meters to show you what is exactly happening in specific sections of your signal path, but don’t forget to trust your ears as well.