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Sound may be recreated by playing back pulses of constant amplitude, properly placed. See link for a coding method deviced by Roman Black. It may also be recalled that some very high quality converters for digital audio use a single bit stream.
So a speaker can be devised by creating explosions at
a high enough frequency, and filtering, or muffling, the resulting stream of explosions.
The NEELCO(tm) explosive speaker consists of a combustion chamber followed by a large horn and some sound filtering inside it to shape the frequency response. Vaporised gasoline and air mixture from a carburettor is fed to the chamber and ignited by a spark plug, which is controlled by the bit stream derived from music according to the algorithm devised by Mr. Roman Black.
Sound encoder software home page by Roman Black
Shows how to encode high fidelity music in a single bit stream [neelandan, Oct 05 2006]
Yamaha have an integrated circuit driving a speaker with pulses
So eliminate the middle man, and produce the pulses by more efficient means! [neelandan, Oct 06 2006]
Halfbakery: The Expode O Phone
Similar? [jutta, Oct 06 2006]
Booooooom!-When loudpeakers catch fire
[Dub, Oct 09 2006]
(O.T) Mutually assured destruction
60" Subwoofer [Dub, Oct 09 2006]
Flame Speaker from 1968 [csea, Oct 09 2006]
[Dub, Oct 12 2006]
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||[jutta] Similiar in the manner of exiting the sound resonator.
||But in the linked idea the explosions set an acoustic resonator into oscillation on a single note (plus harmonics). This idea utilises the filtering effect of an acoustic transmission line to attenuate the higher harmonics and so provide sound approximating to the digital representation.
||Can a gasoline flame be ignited and quenched in 20 microseconds? This would be necessary for high fidelity reproduction. (1/44kHz~= 20usec.)
||Might require catalytic conversion of exhaust products and an exhaust tube.
||See [link] for analog flame loudspeaker from the 1960s.
||[Dub] Thank you! I built one of these using a bunsen burner and a 6V power transformer. It worked, but the noise of the burner was almost at the level of the audio.
||I do recall seeing commercial flame loudspeakers at an Audio Engineering Society convention in the early '70s.
||The guys all look so, well..., hip.
||If you are willing to give up the constant amplitude part, you might be able to modify an ink jet print head to pump out a flammable liquid into an air stream with a glow plug. Or for ramp up, a fuel injector from a car.
||Great links, [Dub], though I couldn't check out the videos. I'm on a slow dialup. And I should try the flame amplification linked to by [csea].