What is RMS?

[monkie]

Can someone help explain what RMS? I only know that it has something to do with volumes but not exactly sure what the reason behind it is.

Thanks

[Massive Master]

Root - Mean - Squared. Average over time, for lack of a better explanation.

[SouthSIDE Glen]

As John said, RMS is more or less the average voltage (volume) level of the voltage levels measured over a sequential series of samples.

It's not a true mathematical average; the calculation for RMS is mathematically different than a simple average, but the concept is basically the same.

The purpose for it - in this subject, anyway, - is that it more closely resembles the volume as perceived by the human ear than simple peak volume level measurements do. For example, something with a peak level of -3dbFS and an RMS level of -10dBFS will actually usually be perceived as louder than something with a higher peak level of 0dBFS but an RMS of only -13dBFS.

G.

[monkie]

Originally Posted by SouthSIDE Glen

As John said, RMS is more or less the average voltage (volume) level of the voltage levels measured over a sequential series of samples.

It's not a true mathematical average; the calculation for RMS is mathematically different than a simple average, but the concept is basically the same.

The purpose for it - in this subject, anyway, - is that it more closely resembles the volume as perceived by the human ear than simple peak volume level measurements do. For example, something with a peak level of -3dbFS and an RMS level of -10dBFS will actually usually be perceived as louder than something with a higher peak level of 0dBFS but an RMS of only -13dBFS.

G.

How should I take this into consideration when mixing?

What is dBFS?

[SouthSIDE Glen]

Originally Posted by monkie

How should I take this into consideration when mixing?

You don't, really. It has some importance when working out recording levels if you're recording to digital, and it can have some relevance (more to some people than others) when mastering and working out final relative volume levels. But during mixing, your main concern is to make sure you keep the peaks under control and let the RMS levels just fall where they fall.

Originally Posted by monkie

What is dBFS?

That is the dB scale used on the digital side of things. The digital meters you see in your DAW are calibrated in dBFS.

For a pretty full explanation on all this stuff, head over to www.independentrecording.net and click on the icon in the lower right-hand corner labeled "Metering and Gain Structure". This will pop up an interactive applet that'll take you though everything you need to know about all the different dB scales and how they relate to each other in real life...including discussions of RMS and dBFS.

G.