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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 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.
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.
3) The northern lights even when they appear to be near and low are
relatively high and, for most observers, far away.
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.
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.
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.
Whatever the answer may be, it is an interesting question.
Yours truly, Dave Webster, Kentville
Steve Shaw wrote:
> Hi Dave,
> In partial answer to the second part (of your query below),
> possibly no-one has tested your thought explicitly because there is no
> reason to suspect it would work. At the same time, the transducer
> mechanisms of ears in various animals are now quite well understood:
> what's know doesn't suggest that the sensory receptors (one type of
> hair cell) are specialized for RF detection, while they clearly are
> specialized for mechanoreception. Perhaps the most obvious thing is
> that people who have offices or apartments right next to cell phone
> relays or broadcasting stations would start to "hear" the radiation
> directly, if your suggestion were true -- they wouldn't need a radio.
> And you'd hear every lightning strike at light speed, not just via
> the sound-wave rumble of thunder seconds later.
> The RF energy would be extremely low unless you were standing right
> next to a transmitter; it's not clear why this would have evolved in
> the first place because no animals including us use this form of
> communication; to use it you would have to have some effective form of
> transducer like your crystal radio, and none is known; most forms of
> external stimulus transduction are beset by 'noise' and use some form
> of early amplification to partially overcome this, and there is
> nothing obvious in the ear that suggests an RF amplifier, while it is
> well established that our ear contains a fairly potent pressure
> amplifier to juice up the sound pressure changes.
> The actual transducer mechanism is known to reside in some of the
> cilia ("hairs") that stick out of one side of this one type of hair
> cell, and which contain small numbers of mechanically sensitive
> membrane ion 'channels' that are shut when it's quiet. When the cilia
> are displaced mechanically by a sound-activated travelling wave on a
> nearby membrane that originated as a pressure wave at a 'window' in
> the ear, little molecular strings called tip links pull on the
> channels, which open and let millions of ions flow through. This
> changes the voltage across the hair cell's main membrane. This story
> is simplified and doesn't deal with frequency tuning, but it's this
> voltage change that causes neurotransmitter chemicals to be modulated
> at the nerve connection from the hair cell to the auditory nerve.
> This in turn causes changes in impulse firing in that nerve, which
> after some more steps results in more nerve impulses further up, which
> finally get interpreted centrally as sound.
> Having said this, it is certainly not outlandish to suggest that
> some other form of energy might be the proper stimulus, and that
> convention has got it wrong, because this has happened historically.
> The classic case is not far from your idea, of electroreception
> (detection of very weak, water-born electric currents). This is a
> sense completely foreign to us, that some fish species use for
> signalling, object and prey detection. The electroreceptor sense
> cells historically went through a sequence of being misinterpreted as
> to their function, at one point being suggested to be temperature
> receptors for instance. People in these fields are now sensitized to
> the need to define the actual natural stimulus used by that system,
> rather than something that also affects it but that's just an
> epiphenomenon.
> Steve
> On 8-Nov-06, at 3:09 PM, David & Alison Webster wrote:
>
>> The article also mentions in passing the enigma of sound generation
>> by northern lights. I have read elsewhere that attempts to record
>> sound produced by the northern lights have recorded only silence [and
>> in another context, cannon roars recorded for the 1812 Overture by
>> conventional methods sounded like a soap bubble bursting]. Many
>> people, including yours truly, have heard the northern lights so one
>> must ask what form of energy is being 'heard'.
>>
>> Is it possible that inner ear papillae can act as detectors for high
>> frequency radio waves generated by electrical discharges ?
>>
>> Yours truly, Dave Webster, Kentville
>
>
>
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