0

This question falls into the funfact category, but I'm anticipating this question from my next course students and I'd like to have the answer, if there is any. In the spirit of English language, RMS is actually the waveform square mean root. However, the abbreviation RMS stands for root of the mean of the square of the waveform. Is there any answer as to why this form is chosen? I haven't been able to find it on Google.

Similar trivia can be found on Wikipedia for lambda expressions. When asked why lambda, Alonzo Church answered "eeny, meeny, miny, moe". Unfortunately, no trivia for RMS.

Martin
  • 103
  • 2
  • 4
    I’m voting to close this question because that is what it is and any questions that seek to understand why the English language tends to work this way are off-topic i.e. frozen chicken vs chicken, frozen (and many other alternative anomalies where the preferred phrase is the other way round such as chicken curry). Try the language(s) section of SE. – Andy aka May 13 '20 at 09:19
  • 2
    The premise of the question is wrong anyway. Square mean root is the order in which the operations are performed, but not how they are read out loud. When the formula is written out, one encounters root first reading from left to right, then mean, then square. So root of the mean of the square makes more sense anyway. Like sum of products. Etc. – user57037 May 13 '20 at 09:23
  • 1
    $ V = \sqrt { \frac {\int_0^T V^2 dt} T} $ is the root of the mean of the squares. – Transistor May 13 '20 at 10:20
  • @Andyaka it is off-topic from the standpoint of electrical engineering, true that. And I pretty much got the answer that makes sense, so closing is fine. – Martin May 13 '20 at 12:37
  • @Martin of course it's fine - I never had a doubt. – Andy aka May 13 '20 at 12:41
  • @mkeith sum of products did cross my mind, but still it is not in the spirit of English to use "this of that", and especially without the "of the" part. When "of the" is omitted, the phrase is by (standard language) default processed backwards: church keyboard stand, not stand of the keyboard of the church, or God forbid stand keyboard church - like root mean square. So the premise of the question is fine. – Martin May 13 '20 at 12:43
  • Well, we read from left to right. So root mean square is reading left to right. square mean root is reverse polish notation. – user57037 May 13 '20 at 18:12
  • @mkeith in common English, which spans a large portion of science, we say things like church keyboard stand, or first-order predicate calculus. That confuses me... why here this direction and there that direction? And RMS tends to fall in minority, multi-word stuff is usually labeled in reverse polish. – Martin May 15 '20 at 04:00
  • We say it aloud as if we were reading it from a written page. The formula is written, from left to right, root symbol first, then the integral is set up to calculate the mean, then finally the function is squared inside the integral. – user57037 May 15 '20 at 04:25
  • @mkeith well yes, I get the point... though I'm kinda closer to accepting the answer down below, that this way of saying it actually draws from the functional notation. Now is there any similar thing that we read in this direction (opposite to street language), some formula that is read in the order that the operations appear? I can't think of any... but anyways I don't really want to bug any more with this question... – Martin May 15 '20 at 06:29

1 Answers1

6

In the language of functions, it's just fine as it is.

If we have a waveform, we first need to square it.

S = square(waveform).

Then we need to average the result.

MS = mean(square(waveform))

Then we need to take the square root of that.

RMS = root(mean(square(waveform)))

Do bear in mind that both conventions are used for whether the operator comes before or after the parameters, neither is 'correct', they are conventions. A lot of purists like reverse Polish notation, seemingly just for the lols. When we go to compute RMS from digitised waveform data, we are usually using a programming language, for which this functional notation is natural. And it's always been called RMS. If you start calling it SMR, nobody will know what you mean, and they'll think you unnecessarily pedantic and strange if you try to insist.

Solar Mike
  • 6,539
  • 1
  • 12
  • 28
Neil_UK
  • 166,079
  • 3
  • 185
  • 408
  • @SolarMike thx, I'm making some typos these days that surprise me, often homophonic. I'm obviously getting senile. – Neil_UK May 13 '20 at 10:08
  • I am finding typos to creep in all too often now and it is annoying when I find one on a slide in front of students - they don't spot them though... – Solar Mike May 13 '20 at 10:43
  • @Neil_UK this seems like a reasonable answer, thanks! Functional way of thinking it probably was, when they coined it. If I start calling it SMR now, sure nobody will understand because the RMS abbreviation is well accepted. And yes, if I'd insist they'd think as you described. I haven't said I would - I was just curious about the reasons for this particular word order. – Martin May 13 '20 at 12:50