Re: The science behind streamer sounds

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>



> Original poster: "Christopher \"CajunCoiler\" Mayeux by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <cajuncoiler-at-cox-dot-net>
>
>
> My first guess is that it's similar to the
> process that makes thunder from lightning.
> ...only on a MUCH smaller scale.
> I believe the collapse of a vacuum had
> something to do with it.

Just had to jump in here... thunder sounds have nothing to do with a
collapse of a vacuum (that's a several hundred year old theory.. not quite
as old as ones about gods arguing, clouds bumping, etc.)

Rapid heating cause rapid expansion causes a shock wave to propagate, which
some distance (several hundred meters at most) relaxes to an acoustic pulse.
The typical stroke is quite long, acoustically (1000 ft/sec.. 300 m/sec), so
you hear the pulses from different parts of the stroke at different times.
The stroke develops in a stepped fashion, as well, lending a bit of fine
structure.

One can, with a suitable set of microphones distributed over the
countryside, actually make measurements of the lightning channel position
(and of supersonic (and other) planes flying over/near).