[ot] Decibels and the ear (was: Re: [plug] Hot and bothered CPU hankers for cool breeze)

[Cameron Patrick]

On Tue, Dec 16, 2003 at 10:25:51PM +0800, James Devenish wrote:

| Okay then, I have no reason to think you're right or wrong (in fact, I'd
| forgotten that decibels may be closely related to aural perceptions,
| since they're also used for general signal analysis). But I'm going to
| stick to good-old 10log(f) for now. So, let's say one machine is 50dbA
| (hey, isn't rounding nifty!). That's 10^{-8}Wm^{-2} (is it?). So 400
| times that would be...60--70dbA?? So that would be, say, 30% louder in
| perception? Well, that would seem to match Derek's story! :)

Yep :-)  You're probably right-er than my original calculations...
although even if your (our?) assumptions are correct so far, that is
still only valid in physics-experiment-land where all the computers are
point sources at exactly the same location.  Presumably Derek wouldn't
necessarily be in the middle of the room surrounded by these machines
and the closer ones would be a good deal louder than those further away.
But then we get into the inverse square law and something-ivity (dammit
I wish I had that Physics book now... for some reason my mind keeps
thinking permittivity but that's electromagnetism-related...
absorptivity?) of all the other objects in the room and my head hurts -
I wish I was better at physics.  (And had a better memory!)

Cameron.