Visualising sound 10
Audio metering

Level of challenge Intermediate

Welcome to this tutorial on audio metering.

Audio meters are essential tools for the project and home studio owner. They provide a visual means to monitor signal levels during recording and mixing.


Caption - Types of meters

There are many types of audio meter, but the five primary types are ..

  • single LED's
  • peak programme meters
  • VU meters
  • phase and correlation meters
  • and loudness meters

Caption - Gain reduction

All of these types of meters can be used to show either signal level or the amount of gain reduction being applied by a compressor or limiter.


Caption - 1. Single LED meters

Single LED meters change colour and intensity according to signal level,. They usually show green when a signal is present and red when the signal is within the headroom of the device or clipping. Some LEDs change intensity, glowing brighter to indicate louder signals.


Single LED meters are often used when cost or space factors prohibit the use of peak programme or VU meters.


Caption - 2. Peak programme level meters

Peak programme level meters, or PPM meters, display the peak level of signals in audio equipment. There are many types of PPM and they all help the studio engineer determine the peak levels in a soundwave signal.


One type of PPM is the True Peak Programme Meter which displays the changing peak level of a soundwave signal. They are used to identify the loudest peak in a signal.


Another type are Sample Peak Programme Meters, also sometimes referred to as digital meters, which display changing peak sample values. These types of meters are used in digital mixers, effect processors and DAWs. Good practice dictates that when using these types of meters 3dB of headroom should be allowed to accommodate inter-sample peaks and avoid distortion. A peak level of -3dB is therefore required.


Caption - Digital 'Over" indicator

Peak programme meters often have a separate indicator which turns red whenever the signal level exceeds that which can be accommodated by the word length of the system. This indicates digital clipping, or distortion has taken place and the level should be reduced.


Caption - 3. VU meters

The VU meter was developed in 1939 to display signal level in audio equipment. Due to the ballistics of its meter, it is unable to show peak levels, or spikes in volume. It is therefore not good at showing peak levels. Interestingly, this limitation makes it better at showing average level, which is loudness, and this explains why it has remained popular. However the VU meter cannot tell us what a recordings average loudness is over it duration.


Caption - 4. Phase and correlation meters

Phase and correlation meters show the phase relationships between the two channels in a stereo signal and are primarily used to indicate how the signal will be affected when summed to mono. A phase meter will show whether a signal has good mono compatibility or not.


Caption - 5. Loudness meters

A recent development in audio metering is the loudness meter. Loudness metering is covered in a separate video tutorial.


Caption - Thanks for watching

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