This was my response to an audio engineer friend of mine who was joking about her daughters being especially good and especially helpful today but doubts they'll be the same girls tomorrow:

"Merry Christmas, ****! Until you convince the powers that be that X-Mas presents are distributed based on RMS naughty/niceness and not peak level monitoring of Naughty/niceness, I'm afraid your prediction for tomorrow will prove correct."

For those unfamiliar with the abbreviation, RMS means "root mean square."

We are such geeks.

ROFLMAO. You do realize that your RMS definition leaves most everyone just as puzzled.

I'm not going to be sucked into explaining the math behind it. It takes too long to do it right. Let's just say that engineers understand it and its significance and the web is indeed a wide, wide world for those who are curious.

For the purpose of the joke, we can just call it a complicated way of calculating a certain type of "average."

RMS. If you see ripples on a pond, how do you describe their height? In some sense, the height of an average ripple is more important than the height of one ripple, but because there is a valley in between each pair of peaks (and a peak between each pair of valleys) the real average height is zero (relative to the water level when there are no ripples). In other words, measuring average wave height over time is useless.

There are two ways around this difficulty. The most obvious is to ignore the valleys and just measure the peaks (one method mentioned by v-dog). Although this is conceptually simple, it turns out not to be easy to measure under most circumstances, and also not particularly useful.

The other way to avoid the difficulty is to square the height before averaging it. Remember that when you multiply two negative numbers the result is positive, so the square of the height is always positive, so the average of the squares has real meaning - it turns out to measure the energy in the wave. If you want to quote the average as a height (I.e. in inches rather than square inches, which may sound odd) you have to take the square root - so the height you quote is the Root of the Mean (average) of the Square - RMS.

As is often the case in math/science, a fairly simple situation like this turns out to be related to a much more complex situation. In quantum mechanics, the probability of finding a particular situation (called a 'state') turns out to be like energy - the square of something more fundamental, the 'probability amplitude'. Or perhaps the relationship is more apparent than real - the only model that scientists had that gave even an approximately correct way of predicting quantum events was the familiar picture of ripples on a pond.

By the way, has anyone ever noticed that when you throw a rock into a pond, the sound comes back in one pulse, but there are many ripples on the surface of the water, the first ripple being the highest? I learned why in my recent Partial Differential Equations class - in an odd number of dimensions (like our three-dimensional space) waves propagate at a single speed, but in an even number of dimensions (like a two-dimensional water surface) there is a 'residue' that travels more slowly. In a two-dimensional (or four-dimensional) world we could neither see nor hear.

V-dog may have experienced that sound quality is very different if it propagates in a space in which one dimension is very small.

That space being a single rack space box with an RMS button on it.

I can't disagree with your explanation of RMS, but I can disagree with the fact that you give no idea od what it sounds like.

That's why I steered clear of the question - but thanks for the simplified math. -G

Quadratic equations next time please.