Re: Amplitude Decibel conversion problem

On Oct 7, 9:14=A0pm, Randy Yates <ya...@[EMAIL PROTECTED]
> wrote:
> glen herrmannsfeldt <g...@[EMAIL PROTECTED]
> writes:
> > Richard Owlett wrote:
>
> >> c...@[EMAIL PROTECTED]
 in *ERRROOOORRRR* wrote:
>
> >>> Even in acoustics, we have 100 dB is 0.946 watts per square meter.
>
> >> I would agree IF *and only* IF you stated dbV, dbm, or db.... with
> >> stated/implied load/impedance/****
>
> > I presume that is for a propagating wave in air. =A0The actual power
> > that goes into some detector (or other medium) depends on the
> > impedance in that medium.
>
> But it's just like the electrical situation - if we assume the
> same impedance for the reference as for the measured signal,
> the two cancel and don't really matter - we can compute it from
> the amplitudes (or equivalently, sound intensities).
>
> I think Richard is right. I think what Clay meant was 100 dB SPL.
> --
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Well when one talks about sound, db specifically refers to sound
pressure level - that is why one doesn't need the "m" or something
else to designate the reference power. Yes one may add the "SPL" to
reduce ambiguity.

Instead of so many watts per square meter, when can equivalently give
a reference in terms of pascals which is simply newtons per square
meter.

As like with the electrical case, the reference units cancel - they
must cancel infact. Arguments of transcendental functions must be
unitless!

Clay