--- In "Bruce Wilson"
<> wrote:
>
> Just to make it clear for those who don't know radio scattering methods,
> these are recordings not of the sound the meteors make when entering the
> atmosphere (they don't seem to make much sound at all, radio or
aural), but
> the sounds of over-the-horizon FM radio stations that reflect off the
> ionized trail in the wake of a meteors passage and become audible
for a very
> short time, the duration of the ionized trail.
>
> They aren't strictly nature recordings, but they are very interesting.
To take this Off Topic subject just a little further:
In 2001/2002 I helped the ESA (European Space Agency) do some tests
during the Leonids showers.
The technique was different to that described by Bruce above and
involved recording the doppler shift, caused my a meteor's ionisation
trail, of an unmodulated BBC short wave radio transmission. My
involvement was due to my location relative to the transmitter being
suitable for recording the doppler shift using the R-meteor
spectrogram program
http://sapp.telepac.pt/coaa/r_meteor.htm
Some spectacular dopplergrams were obtained. The following links give
more detail of the experiment
http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=3D29005
http://www.meteorobs.org/maillist/msg24252.html
By converting the hf doppler changes to audio frequencies it was
possible to "hear" the visual traces. This web page gives a link to a
.wav file of the sound of the trace
http://www.esa.int/esaSC/SEMSS0XLDMD_sensations_0.html
I understand the plan was to collect dopplergrams of the sane meteors
as they appeared at different points on the globe. From this info it
would be possible to develop a three dimensional dopplergram and
thereby gain more understanding.
I forwarded my dopplergrams to the ESA but never heard anything again.
As I said, at the beginning of this post, this is off topic but it
does have a whiff of sonogram analysis about it ;-)
Cheers
Tom Robinson
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