> From: glen_moore.science_po@central-gw.uow.edu.au (Glen Moore)
> Newsgroups: sci.astro
> Subject: Re: Audible Meteors
> Date: 20 Aug 1993 17:39:17 +1000
> Organization: University of Wollongong
>
> I undertook a study of a meteor which fell in southern Australia several years
> ago and was heard over an area of over 10,000 square miles. This study was
> reported in Australian Natural History magazine.
>
> We interviewed eye (and ear) witnesses over a two week period and I
> remember being impressed by the large number of electrophonic reports. The
> area was a rural one and the fall occurred at a time when many people were
> outdoors.
>
> Many people heard sounds and <then> looked up to see the meteor, later they
> heard 'thunder', 'distant gunfire' or similar sounds. In many cases people
> were in the vicinity or sheet metal buildings (common in farming areas).
> Crackling and hissing was the most common description.
>
> Also common were animal stories where the animals reacted at the time of
> the visual sightings but before the 'thunder'. e.g. cat runs up wall, farm
> dog tries to enter house, horse throws rider.....
>
> After the many interviews with 'down to earth' farmers I was left with
> no doubt about the reality of electrophonics. Perhaps a person in 10
> may have experienced the effect in this fall. 
>
> Incidentally we found trees damaged and felled as if by shock wave in the
> position triangulated from observations of the terminal cloud (within a
> square kilometer) but with the rugged, heavily treed terrain we never found
> any material.
>
> Hope this is of help.
>
> Glen Moore
> Science Centre, Wollongong
> gkm@cc.uow.edu.au    fax: 61 42 213151  (61 = AUSTRALIA)
>
________________________________________________________________
In article <1993Aug20.110311.1@cc.newcastle.edu.au>,
phcslk@cc.newcastle.edu.au (COLIN KEAY) wrote:
> 
> Newsgroup: sci.astro
> 
> Topic: The instantaneous sound of meteors
> 
> Yes, It's real. But rather rare. The average person may hear one in
> a lifetime. But if a person spent all night every night outdoors,
> the number could rise to about ten. A meteor fireball needs to be
> brighter than about -9 mag. to give rise to sustained electrophonic
> sounds (as the sounds simultaneous with the sight of meteor
> fireballs are now known). Although brief electrophonic sounds (like
> "pops" or "phuts") can be generated by fainter fireballs, down to
> maybe -6 mag, if they explode. It is a purely physical effect not to
> be confused with electrophonic hearing, which is physiological.
> 
> Back in the time of Edmund Halley, such meteor fireball sounds were
> thought to be purely psychological, a view held by some meteor
> scientists until quite recently. And there is also Ben Zellner's
> theory about the bones crackling in his neck when he looks up (must
> be painful to use telescopes as much as Ben does!).
> 
> The mechanism of sustained (longer than a second or so)
> electrophonic sounds is fairly straightforward (see Keay, SCIENCE,
> vol 210, pp 11-15, 1980):
> 
> 1. If a meteor fireball penetrates deeply enough into the atmosphere
> to enter the continuum flow regime, and its plasma trail becomes
> turbulent, it can trap, scramble, and later release the geomagnetic
> field, producing megawatts of ELF/VLF (audio-frequency) electro-
> magnetic radiation in the Earth-ionosphere cavity.
> 
> 2. The electric vector of the e-m radiation can cause mundane
> objects (hair, pine needles, whatever) to vibrate at twice the e-m
> frequency, that is, act as transducers to produce audible sound.
> Nature's little loudspeakers. This has been verified by laboratory
> experiments in anechoic chambers, and published.
> 
> 3. Under reasonably quiet conditions the hissing, swishing or
> crackling noises are audible to humans, often serving to draw
> attention to the fireball before it is detected visually.
> 
> And that is essentially the explanation. The model satisfies Occam's
> Razor in its economy of principles. But for a decade it did have me
> a little bit apprehensive about its validity because I could find no
> records of the ELF/VLF signals from fireballs. OK, so electrophonic
> meteor fireballs are very rare and no ELF/VLF records had ever
> revealed them.
> 
> So I didn't push my model too hard until one fine day in Japan in
> 1990. There Dr T Watanabe showed me a chart recording from a VLF
> receiver with timing matching the photometry of a fireball
> photographed by K Suzuki and his pupils, one of whom heard the
> fireball electrophonically. A colleague, Dr T Okada, obtained the
> signal spectrum - 500 Hz to about 8 kHz. These records blew my mind.
> It was my most exciting experience in 40 years work in science.
> 
> I believe the Japanese feat has recently been repeated by Dr Peter
> Brown of Canada. I'm dying to see his results.
> 
> Anyway, meteor fireballs are not the only progenitors of
> electrophonic sounds. Having interviewed Canadians who have heard
> sounds produced during extremely intense auroral displays, I'm
> fairly sure they are similar. Reports of people hearing "clicks" and
> "vits" coincident with lightning flashes are probably due to the
> same process, since it is well known that lightning produces strong
> e-m transients. Another geophysical mystery is the existence of many
> anecdotes about the alarm exhibited by animals immediately before an
> earthquake: there are records of seismically generated ELF/VLF
> signals, which, by propagating much faster than seismic shock-waves,
> may alert the animals. The transducers may be the loose hair which
> many animals have in and around their ears. Maybe there are other
> effects which can be similarly explained by my model.
> 
> If the above four examples of electrophonic sound production are all
> verified I believe we could say that a new branch of science has
> been born: Geophysical Electrophonics. Who knows what it may lead
> to.
> 
> It is clear from the sci.astro news contributions that there are lot
> of folk out there who don't know about the progress that has been
> made in this field over the past fourteen years. An invited review
> article "Progress in Explaining the Mysterious Sounds Produced by
> Very Large Meteor Fireballs" is about to appear in the Journal of
> Scientific Exploration (with 70 refs). I wrote another article on
> the subject for Scientific American, but they wrote back saying they
> were not interested in the topic. Any suggestions for a respectable,
> widely-read journal that might be interested in an up-to-date
> presentation of the subject?
> 
> Lastly, I would appreciate any first-hand witness accounts of any of
> the four electrophonic phenomena mentioned above. They can be e-
> mailed to me, or sent by ordinary mail (especially if other
> supporting material is available).
> 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> +  Colin  Keay            :::::::                  Shame physics is not a  +
> +  Physics Dept                :::::               pseudo-science.  Would  +
> +  Newcastle Univ                   :::\ | /       be ahelluva lot easier  +
> +  NSW, AUSTRALIA 2308                 - o -       to raise public money.  +
> +  PHCSLK@cc.Newcastle.edu.au          / | \            - Cynicus Maximus  +
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++