RMS (Root Mean Square) — What It Means in Music Production
RMS is a measurement of the average power of an audio signal over time, calculated as the square root of the mean of the squared amplitude values. It provides a closer approximation of perceived loudness than peak measurements, though LUFS has largely superseded it as the standard loudness metric.
Full Explanation
RMS calculates the effective average level of an audio signal by squaring all sample values, averaging them, and taking the square root. This mathematical approach gives more weight to higher amplitude values, making RMS a better indicator of perceived loudness than peak level. A signal with tall, narrow transients (like a snare hit) might have a high peak level but low RMS, meaning it sounds quieter than a sustained synth pad with the same peak level but much higher RMS.
RMS is typically measured in dBFS (decibels full scale) and displayed as a moving average on meters. It was the primary loudness measurement before LUFS became the standard. The key difference is that RMS does not apply any frequency weighting, so it treats all frequencies equally, while LUFS applies K-weighting to match human hearing sensitivity.
Despite being superseded by LUFS for final mastering decisions, RMS remains useful for comparing the density of different elements in a mix, checking compression ratios, and understanding the overall dynamics of a track. Many producers still reference RMS values alongside LUFS during the mixing stage.
In Electronic Music
In electronic music production, RMS is still valuable for evaluating individual elements in a mix rather than the final master. Comparing the RMS of your kick drum versus your bassline, for instance, helps ensure the right balance of power between them. Electronic genres with heavy compression (tech house, dubstep) tend to have RMS values close to their peak values, while more dynamic genres (ambient, deep house) have a larger gap between peak and RMS.