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Take a resonanting cavity with flexible,
diaphragm-like ends, filled with gas at
some suitable density. Rapidly heat the
gas with microwaves (or other EM radiation
as appropriate) to generate pressure waves
and so sound. It'd probably have really
bad sound quality, but it might be a neat
toy.
Problem: how to cool the gas
rapidly when necessary?
Pyrophones
http://www.windworld.com/emi/pyronw.html
A similar idea, but with a gas flame. [krevis, Apr 28 2000, last modified Oct 04 2004]
Plasma Tweeters
http://members.aol....ann2/plasma/ion.htm
Believe it or not, some of them dang fool audiophile-types already done it. Ionize gas with a high-voltage discharge; the resulting plasma is electrically conductive. Pressure waves, hence sound, are generated by changing the electric field near the plasma. The ultimate high-end gear: expensive, vastly inefficient, and dangerous (the discharge that produces the plasma also produces ozone). But if you need frequency response into the range of dogs, bats, and radio, plasma's your answer. Course anything that expensive probably Sounds Real Nice. [rmutt, Apr 28 2000, last modified Oct 04 2004]
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Annotation:
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Don't use microwaves; use IR lasers
in some frequency absorbed by air.
That way you can just heat up a
thin slice of air, which should
cool quickly. |
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Sound quality could actually be
quite good, especially since you
could steer the laser with an AOM
for true sonic imaging. |
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(It would double as a bug zapper!)| — | egnor,
Apr 29 2000, last modified Nov 30 2000 |
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May as well let on the other idea that came immediately thereafter, cosma: |
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Set of headphones which use intense but tuned EM to produce the perception of sounds in the wearer's sensorium by (a) inducing physical vibrations detected by the normal hearing mechanism, or (b) inducing the sensation of sound directly in the portion of the brain responsible for processing auditory (and maybe visual, too) inputs. |
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Avoid standing near a computer while wearing these, though. |
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Eek! With all the problems that just talking on cellphones is supposed to cause, do you really want 'intense EM' emitters on both sides of your head? |
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i think a detail we're overlooking here is the fact that the speaker functions via heat. as in, it's gonna get really hot. normal speakers can be picked up, or you can put piles of paper near them and they won't burst into flame. |
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Someone built a motion simulator that
stimulates the inner ear directly, and of
course hearing-aid researchers have
cochlear implants and such. |
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(I'm too lazy to look up URLs for you this
time, sorry.) |
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OK, so we slap a big "Caution: Speaker
Is Hot" warning label on it. I imagine that
would only _increase_ sales, and could
be put to good use in rock concerts and
other sorts of performance art. Support
the actual sounding body by metal
struts which in turn rest on a dense,
high heat-capacity base, done up in
a nifty dead black. |
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Would look -really- cool in a concert, a bunch of clear Pyrex tubes with flashing flames inside them... |
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As resident know-it-all, a few technical corrections: neither microwaves nor IR lasers will heat air, which is transparent to both. (Otherwise microwave ovens and CD players would only work in a vacuum). Also, electrostatic speakers don't make the air expand, they make a charged membrane vibrate, which moves the air. |
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Air does absorb many frequencies of IR (depending on the amount of water vapor and CO2 present, among other things). It's transparent to the frequency used for CD lasers (though that laser really doesn't have to go through very much air in any case). |
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rmutt: Plasma speakers != electrostatic speakers. Plus, plasma speakers are GREAT for reproducing high frequencies, but don't expect them to put out ghetto-fab bass. |
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