RMS (Root Mean Square) is a time-averaged measure of a signal's amplitude — square the samples, average them over a window, take the square root — which tracks the energy in the sound rather than its instantaneous spikes. Because perceived loudness depends on sustained energy, RMS correlates far better with how loud something sounds than peak does, and it underlies the level detection inside compressors and limiters. For loudness compliance it has been superseded by LUFS, which adds the frequency weighting and gating that RMS lacks, but RMS remains an everyday tool in metering, dynamics processing, and quick level comparisons.
The book · Volume 4 of 7
Audio for Video: A Complete Guide to Sound in Video Products: From PCM and Codecs to Loudness, Accessibility, and Real-Time Voice Processing
RMS tracks the energy of a signal better than peak, but it is not the same as perceived loudness and will not satisfy modern delivery specs. This volume explains RMS in detail next to peak, true peak and LUFS measurement, so you know where RMS is still useful and where loudness meters must take over. Written by Nikolay Sapunov, CEO at Fora Soft.
Using RMS levels for loudness and getting files rejected by platforms?
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