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It has to come out the same either way. Sort of like when you use the
DB formula and use power as a reference or use voltage as a reference.
Since power P = V^2/R and R is constant, if you reference the voltage
you need to use 20 log and if you reference power it is 10 log. It
comes out the same either way. 3 db is double the power and a
perceptible change in the perceived volume.
Her is some info on it I found on the web
http://www.neurophys.wisc.edu/~ychen/textbase/s1-p6.html
Ralf Kuchenhart wrote:
>
> Ian Horsey schrieb:
>
> > All there is to know about dB :
> >
> > The sound intensity level B (beta) is given by (10dB) x log I / Io
> >
>
> [...]
>
> > Back to ordinary dB - an intensity increase of a factor of two leads to a
> > 3dB increase in sound intensity level. This change is barely perceptible to
> > the human ear, and most people usually equate an increase of 8 to 10dB in
> > sound intensity level to a doubling of loudness.
> >
> > So there is a point in doing a degree in Electronic Engineering! Hooray!
>
> Well, that's what you learn with an degree in Electronic Engineering, if you had
> some lessons in acoustics you would learn something more (or different?)....
>
> I don't know the exact Englisch words for "Schalleistungs(pegel)" and
> "Schalldruck(pegel)". I would say sound power and sound pressure.
>
> The formular for sound power level is 10(dB)* log (I/Io), but the formular for
> sound pressure is 20(dB)*log (p/p0). If you regard the (electrical) power you
> need in your amps and to drive the speakers, your formular is absolutely right,
> Ian, but if you regard the electric level you record from the microphone, you
> have to use the formular for the sound pressure. Therefore, the step of 1 bit in
> the PCM code is always 6(.02) dB, not 3(.01) dB.
>
> Ralf
>
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--
Jim Coon
Not just another pretty mandolin picker
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