Re: Real-time sound cyphering algorithm

From: David Eather (eather_at_tpg.com.au)
Date: 05/31/05 

Date: Wed, 1 Jun 2005 02:07:08 +1000

Unruh wrote:
> "David Eather" <eather@tpg.com.au> writes:
>
>> John E. Hadstate wrote:
>>>>> signal-to-
>>>>> noise of 40dB, which is 10,000-to-1 in sound power.
>
> Perfectly correct.
>
>>>>
>>>> IIRC, when I went to school, audio volume was measured in
>>>> dB - spl
>>>> (sound pressure level, which I noted in the pervious post)
>>>> which is
>>>> 20 x log10 and not 10 x log10 which is a measure for
>>>> comparing power
>
> Yes, and he discussed power.
>
>>>> - - you did not do your basic research. Try -
>>>>
>>>> http://en.wikipedia.org/wiki/Sound_unit
>>>>
>>>> Forty dB is a factor of 100.
>
> No it is NOT 100 in power. It is a factor of 100 in amplitude.

Yes that is what I said a factor of 100 is equivalent to 40dB spl.
dB(spl) is the correct measure for sound pressure, dB(p) (and dBm etc) is
not. I only ever spoke about volume. I used the correct units. Brian
introduce the power unit and that unit is not the correct one for volume.

>
>>>
>> The relevant measure for acoustic intensity (volume) is dB(spl) and
>> 40dB(spl) = 100
>
> Intensity is related to power not amplitude. Read your physics texts.

OK. I see your point - my use of the word "intensity" is incorrect - sound
pressure, sound pressure level are the correct terms for discussing volume -
I would have used "volume" but I wanted to avoid a discussion of how you
could make more volume (as in size) by just turning a nob.

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