Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!sunybcs!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: Sound Amplification by Combustion
Summary: Pyroacoustic reproducers... :-)
Keywords: singing flames
Message-ID: <3344@kitty.UUCP>
Date: 20 Aug 89 20:01:32 GMT
References: <11652@cit-vax.Caltech.Edu> <1625@jato.Jpl.Nasa.Gov>
Distribution: usa
Organization: Recognition Research Corp., Clarence, NY
Lines: 34

In article <1625@jato.Jpl.Nasa.Gov>, morris@jade.jpl.nasa.gov (Mike Morris) writes:
> In 1969 I was touring Cal Poly Pomona during a science fair, and an exhibit
> there was a "singing flame".  The student told me the original info was from
> a old Popular Electronics or Radio Electronics.
> 
> The flame has excellent high frequency response, but a lousy low end.
> It must be "doped" with some kind of a glass rod.
> Sorry, that's all I remember.

	I built one myself during the mid-60's when in college, and I recall
getting the idea from an article in Popular Electronics.

	I used an old David Bogen 100 watt PA amplifier, an AM modulation
transformer, and a variable high voltage power supply (1 kV max).  A glass
rod was used to "seed" the flame with sodium ions and render it more
conductive.  I used two insulated carbon rods as electrodes (one cannot
use the burner itself as one electrode since the flame is "insulated"
from the burner).

	It really worked and reproduced sound.  I found that the best
reproduction occured with higher velocity flames.  I first used a laboratory
blast burnder for glassblowing which used compressed air and natural gas
(okay, so I built it in a university research lab on their time :-) ).
It also worked with an acetylene-air Prestolite torch.  The best results
were obtained with the hot, high velocity flame of an oxyacetylene welding
torch.

	It was an interesting project which exhibited good high frequency
response, but not too practicable for use in the living room. :-)

<>  Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.
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