If you’re becoming an audio geek, there’s a lot of terminology thrown around among audiophiles that may be a bit hard to follow without added context. If you’re new to how music is recorded, mixed, and mastered, there’s a lot to learn. One term that can get a bit confusing is how there’s more than one kind of audio measurement represented in RMS, short for root mean square. More broadly, root mean square refers to a mathematical equation that’s somewhat self-explanatory if you know what those terms mean, as it’s the square root of a number set’s mean square.
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In audio, RMS can be used to represent two different things. One is a speaker or amplifier’s peak power rating, where, for example, a speaker rated at 150 watts RMS can safely handle a 150-watt continuous load. The other, perhaps more common usage of RMS in audio, comes in relation to dynamic range, the difference between the sounds in a given track with the highest and lowest volume.
In terms of dynamic range, RMS refers to the average loudness across an entire waveform, with loudness, in this context, referring to perceived volume. Two tracks could have the same peak volume levels, but the one with less dynamic range is going to be perceived as the louder of the two. This comes up most often as part of discussions of what was dubbed the “Loudness War.”
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