Lightning, was Re: Echo Location

The rumbles that follow a lightning crack are reflections of
the sound, 
largely from clouds. The clouds are very diffuse and very
large, so they 
act as low-pass filters (one could probably explain this in
various 
ways). The distances involved provide long delays, whereas
the initial 
crack is the sound of the lightning coming directly to you.
The sound 
itself is from the rapid expansion of the super-heated air.
I believe 
that if lightning extends over a time of perhaps a few
seconds with many 
branches that the timing and varying distances of the
branches will lead 
to more than a single crack, and I recall some interesting
lightnings 
sounds with more of a crackling of high frequency pops and
their 
evolution. However, since a complex sound could also arise
from 
reflections off of buildings, I can't be sure how those
complex sounds 
came about.


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Yes indeed, we have our hands full. I don't own a gun, but
apparently,
certain, high velocity shots start with a SHOCK wave. For
sure, a
lightning crack starts with a shock wave, even though, there
is no
moving object. 

-PB

On Thu, 04 Oct 2007 17:35:17 -0400, "Roger
Dannenberg" <rbdcs.cmu.edu>
said:
> The rumbles that follow a lightning crack are
reflections of the sound, 
> largely from clouds. The clouds are very diffuse and
very large, so they 
> act as low-pass filters (one could probably explain
this in various 
> ways). The distances involved provide long delays,
whereas the initial 
> crack is the sound of the lightning coming directly to
you. The sound 
> itself is from the rapid expansion of the super-heated
air. I believe 
> that if lightning extends over a time of perhaps a few
seconds with many 
> branches that the timing and varying distances of the
branches will lead 
> to more than a single crack, and I recall some
interesting lightnings 
> sounds with more of a crackling of high frequency pops
and their 
> evolution. However, since a complex sound could also
arise from 
> reflections off of buildings, I can't be sure how those
complex sounds 
> came about.
> 
> 
>
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ty-nyquist
-- 
  paul beach
  sniffyravenfastmail.fm


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