clay@[EMAIL PROTECTED]
writes:
> On Oct 7, 9:14 pm, 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. The 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.
>> --
>> % Randy Yates % "Watching all the days go by...
>> %% Fuquay-Varina, NC % Who are you and who am I?"
>> %%% 919-577-9882 % 'Mission (A World Record)',
>> %%%% <ya...@[EMAIL PROTECTED]
> % *A New World Record*,
ELOhttp://www.digitalsignallabs.com
>
Hi Clay,
> Well when one talks about sound, db specifically refers to sound
> pressure level -
I agree with that ...
> that is why one doesn't need the "m" or something else to designate
> the reference power.
Well, if you don't, then the reference power is unknown.
That's why stating (even within the context of sound power) "100 dB is
0.946 watts per square meter" isn't really correct, just as stating "100
dB is 39.2 watts into the load" would not really be correct. It isn't
absolute power unless the reference power is explicit, and with a simple
"dB", the reference power isn't explicit.
Every time someone uses the "****d" term "dB", the reference level has
been somehow specified in the context; e.g., "My satellite LNA output
power level is 4 dB higher than it was yesterday."
--
% Randy Yates % "I met someone who looks alot like you,
%% Fuquay-Varina, NC % she does the things you do,
%%% 919-577-9882 % but she is an IBM."
%%%% <yates@[EMAIL PROTECTED]
> % 'Yours Truly, 2095', *Time*, ELO
http://www.digitalsignallabs.com
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