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

[James Devenish]

In message <20031216141017.GB9236 at erdos.home>
on Tue, Dec 16, 2003 at 10:10:17PM +0800, Cameron Patrick wrote:
> | Of course, talking about power might be more practical since it
> | relates readily to energy. But I think "louder" would be a perceptual
> | phenomenon and we'd have to ask the audiologists.
> 
> Okay, I was pretty sure I remembered from year 12 physics (which I
> understand I've done a lot more recently that you...) a rule of thumb
> saying that 10dB intensity increase corresponds to a 2x increase in
> perceived volume.
[...]
> Certainly I was left was the impression that human hearing was vaguely
> logarithmic (hence the prevalence of decibels when measuring sound
> pressure levels).

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! :)