Mark Taylor schrieb am Mon, 10 Jul 2000:
> > Why I attenuate 3dB (0.7 != -1.5dB) here is that there is a description
> > in Zwicker's book that peak of masking is 3dB below masker. Why I
> > increase masking by 2dB later is that I tuned this value by listening
> > tests.
> >
>
> I dont know if this is correct, but the definition used in LAME is db
> = 10*log10(E) where E is an energy (not amplitude). 10*log10(.7) =
> 1.5db
There is a relation between sound pressure level and sound intensity level
if there is a plain wave (in german "ebene Schallwelle")
L = 20*lg(p/p0) dB = 10*lg(I/I0) dB
p0 := 2E-5 Pa
I0 := 1E-12 W/m^2
1W = 1 Nm/s
for coherent sounds one uses the sound pressure
(coherent sounds: pure tones of the same frequency or sounds from the same
source)
for pure tones: p(t) = p' cos(wt) , p' sound pressure amplitude
for incoherent sounds one uses sound intensity
(incoherent sounds: noise out of a continuing frequency spectrum)
Robert
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