Re: Doppler Distortion - Fact or Fiction?

From: Richard Herring (junk_at_[127.0.0.1)
Date: 08/23/04 

Date: Mon, 23 Aug 2004 09:45:45 +0100

In message <cg67f10jk2@enews3.newsguy.com>, Bob Cain
<arcane@arcanemethods.com> writes
>
>
>Richard Herring wrote:
>
>> In message <cg1ibl0266t@enews4.newsguy.com>, Bob Cain
>><arcane@arcanemethods.com> writes
>> [big snip]
>>
>>>
>>> Whatcha think?
>>>
>> I think you missed my point about the pressure being a linear
>>function of piston displacement _evaluated at a retarded time which
>>depends on the piston's position_.
>
>Nope, I attempted to describe why it isn't correct in the case of a
>piston in a tube. Another simple arguement for the lack of any kind of
>Doppler distortion in that situation, assuming SPL's are low enough to
>keep the air in its linear regime, is that the radiation impedence seen
>by anything driving the piston is identically the characteristic
>impedence of the air, real and frequency independant. Given that,
>where is there room for any error in the process?

The fact that radiation impedances and characteristic impedances have
nothing to do with the mechanism?
>
>> All the physical processes are individually 100% linear, but the
>>outcome is not.
>
>Odd, that. I just don't understand how that could possibly be.
>
Galilean relativity. Speaker displacement x = F(t). Pressure at the
other end of the tube p = L( F(t-x/c) ) where L is some linear operator. 

-- 
Richard Herring