Peak vs RMS

Peak levels are the highest digital values that are in the waveform as it exists in the computer (or other digital equipment). While peak levels aren’t directly related to how we hear the sound, they are crucial for correct gain staging in digital gear. Most critically, peak levels must not reach 0dBfs when recording or when preparing audio for distribution.

There are many factors other than raw level that influence the way we hear sound, which is why peak level alone isn’t directly related to how we percieve sound. For example, we perceive longer sustained sounds to be louder than short transient sounds. Likewise, we percieve sounds in the upper mid frequencies (around 2.5kHz) to be louder than sounds with extremely low or high frequencies (such as 100Hz or 10kHz). So a 100ms sound at 100Hz will sound much quieter than a 1000ms (1s) sound at 2.5kHz, even if they’re both at the same peak level.

RMS is a way of measuring audio levels that more closely reflects how we perceive sounds. Roughly speaking, RMS measurements average the level over time, so that short transient peaks don’t have as much influence as longer sustained sounds. This way the RMS measurement is less “jumpy”, and better represents how the audio sounds to us.

-Kim.

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    • Itamar
    • August 11th, 2010

    Hi, that was great. Thanks a lot for the explanation.

  1. No problem – glad you found it useful!

    -Kim.

  1. July 20th, 2009
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