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Hi Dave, Jean, etherealists all... On the phenomenology, I knew nothing about this so took up Jean's suggestion and googled <aurora, sound> and a couple of other combinations. Most of the 3 million sites found sell commercial audio/video, but there are a few to the point. From spending a 1/2 hour on this last night, the first thing apparent about why auroral sounds haven't been explained satisfactorily is that this is not a robust phenomenon at all. The accounts of the actual sound structure are variable, some hear the sounds when sometimes others in the same group don't, some individuals who hear them sometimes don't hear them most other times, and (perhaps related) this seems to depend on the local structure of the environment, etc. Some outside observers doubt it is a real phenomenon at all, and all seem to agree that the effects are not loud. Perhaps it's not as far out as studying SETI, but it's difficult to approach something like this scientifically when it's so confusingly variable from every angle. Might not be a wise mid-career move to get into this if you are in acoustics, which is probably why there is little real acoustic info on it. If you want more description on this (Jean), maybe try www.auroraborealisyukon.com/faq/ members.tripod.com/~aurorasounds/#em www.acoustics.hut.fi/projects/auroraASoundNews The last one and a download describes some impromptu Finish recordings that were technically compromised by wind and by a power supply problem, but from which allegedly can be extracted excess sound in a band around 100 Hz, which is a bit low for hissing and rustling. The Danish stuff you remember is mentioned, but not in much detail at www.astronomycafe.net/qadir/q1852.html (to amplify the sounds, the individual stuck a microphone at the focus of a radiotelescope dish when they had it turned off and weren't using it.) One of these sites, I forget which, has about six explanations for a possible mechanism of sound production or for hearing it, but as they admit, none completely hangs together. The closest to me seemed to involve brush discharges from sharp things like pine needles or metal eyeglasses very near to the listener, just possible during the vastly stronger electromagnetic fields found in the air at ground level during auroras. This discharge might give a faint rustling or crackling sound, but then apparently would be expected to be accompanied by visual manifestations (St. Elmo's fire) but isn't. Overall, my impression is that there is something out there sometimes (and it's not tinnitus or auditory hallucinations), but that the phenomenon is capricious and objective acoustic measurements on it are few and unsatisfactory so far. As there are neither hard facts nor convincing explanations so far, it's tailor-made for web-type speculation. I didn't try googling <aurora, sound, Roswell> but I'd bet there'd be a few hits. Quoting David & Alison Webster <dwebster@glinx.com>: > Hi Steve & All, Nov 11, 2006 > I agree that that the ear is above all an organ of hearing and, > fortunately, it is not well designed to pick up either the local > radio station or short wave broadcasts. Radio reception requires a > tuned circuit that selectively and efficiently absorbs energy only > from a narrow range of RF frequency while excluding energy from other > ranges. > The more elemental RF detector, the filings coherer (iron filings > in a non-coductive tube), served as receivers for spark transmitters > by using the faint RF signal to increase Direct Current conductivity > of the coherer and the latter in turn controlled current in a battery > powered bell circuit. It is this kind of crude RF detector that just > might (and no we don't have iron filings in our ears) by sheer > coincidence be located in some ear component. And to get from RF to > audible this crude detector might, e.g. switch on when RF exceeded a > certain frequency or amplitude and switch off when levels dropped > below threshold. If these fluctuations were within audible range then > one would have an audible signal. [I don't believe it either, but actually, as came out in the search for magnetic receptors in pigeons or bees, looking for iron or something similar, in principle you'd only need a few tiny domains in a few nerve cells to do it. It is difficult to rule out such small amounts of because of the contamination problem present even in a 'clean' room]. > I really didn't intend to suggest that an RF mechanism was a > defensible idea; apart from being one that comes to mind by > connecting known dots. Briefly these dots are: > 1) Something associated with the northern lights, generates some > effect which we perceive as a rustling sound. [well, it's not an acceptably reliable phenomenon -- see comment above] > 2) This 'sound' is loudest, as I recall, when curtain flickering is > most rapid but, in any case, is associated with concurrent changes in > the curtains. [One site agreed with this account sometimes, but said other accounts disputed the supposed synchrony) > 3) The northern lights even when they appear to be near and low are > relatively high and, for most observers, far away. [apparently it is known that the bottom edge is actually ~100 km up or more] > 4) This effect thus travels at about the speed of light; ending in > our ears as 'sound' it must start and travel as some electromagnetic > wave or some other relatively instantaneous electrical effect. [yes, this agrees with the brush discharge idea] > 5) This effect must be in some way converted within our ears by some > kind of transducer; either to motion of the sound sensitive hairs or > to some stage in sound perception that follows hair motion. [not likely and not necessarily - instead could be a nearby actual external sound, induced somehow by a strong electric field or field change, propagated from the aurora -- brush discharge] > 6) The transducer would not have to be exceptionally efficient > because the northern lights involve impressive amounts of energy; one > million to 10 million amps and about one trillion Watts. [yes but haven't you forgotten the inverse square law acting over 100 km? No-one would suggest that this wattage is delivered to a point near the observer. You are also about to slide into the ELF field debate (extremely low frequency fields set up in the neighborhood of power lines, electric blankets). This is a contentious area to do particularly with currents induced in bodies situated under high voltage power transmission lines or heads next to cell phones, that might produce significant effects on body systems (or not). I'm not sure without going back, but think that the field strength would be smaller at the ground during an aurora. The conclusion in the transmission line case seems to be that the currents induced are relatively small and superficial on the body, but that more study in needed to certainly rule out that there is no significant effect at all in any body system. For a rather heavy technical review of some years ago, in a different league from the fluffy stuff above, try www.inchem.org/document/ehc/ehc