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Re: That hiss

Subject: Re: That hiss
From: Walter Knapp <>
Date: Wed, 30 Mar 2005 15:19:13 -0500
From: Mike Feldman <>

> 
> Walter Knapp wrote:
> 
> 
>>>>> About the only true no sound situation is a absolute vacuum.
> 
> 
> You ain't seen nothing, yet.
> 
> 
> Jeremiah Moore wrote:
> 
> 
>>> I suppose at absolute zero there will also be no sound, i.e. no 
>>> molecular movement.

At absolute zero the mic diaphragm would probably shatter from just a 
gas particle hitting it.

But, then, at absolute zero or a perfect vacuum we would probably have 
other things on our mind than recording birdcalls. So would the bird.

> You ain't seen nothing, yet.
> 
> 
>>> But as we all know, absolute zero is theoretical 
>>> as is a perfect vacuum.  There's always sound, however slight.

True.

> Absolute silence is what happens in the intervals between
> impacts of any air molecule with the diaphragm.... oops,
> there's that danged moving average.

The other problem is that the impact produces wave vibration in the 
diaphragm, which takes a little time to die out. Otherwise the sound you 
would get would just be the sharp impacts. Though that is one of the 
types of self noise, the impact sounds from thermal movement of the gas 
particles.

Of course when you start talking about sound on a particle by particle 
basis then things get funny. It takes the hits of multiple particles to 
make a waveform, or so it would seem.

Walt




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