|MadSci Network: Other|
Interestingly enough, I caught a reference to this article when I was in elementary school - they showed a diagram of the set up for having sound come from a flame, the signal being supplied through electrodes in the flame - basically using a flame as a loudspeaker. Cool! However, the reference I caught was in the "Weekly Reader" - not exactly what you are looking for in your inquiry - but it shows just how intriguing the thought of having sound come from a flame rather than from speakers is! Nowadays, you can see an exhibit of this phenomenon at the Exploratorium in San Francisco.....here is the link for the site: Exploratorium Flame Speaker The original article you mention was in the May 1968 issue of Popular Electronics. The equipment requirements are the audio signal superimposed on about 600V DC, 300mA fed into a 15 cm flame. The article contains a schematic diagram and photographs of the setup. The varying electric field causes the charged particles in the flame to move, creating sound.(This information is from a chemistry education discussion thread response by Bruce Toback of OPT,Inc, in Phoenix, Arizona). Another response from this discussion thread is from Tom McDonald of Harbor Springs High School in Michigan: "I did this flame speaker about twenty years ago. I'm sorry to say that I have no references, but I know we did have to use a wick (asbestos) to introduce K+ and NO3- ions into the flame. I had a student at that time who was really into ham radio and supplied a high voltage power supply and an amplifier. I believe we used two nails as electrodes, one at the top and one at the bottom of the flame. We tried a bunsen burner and also a Fisher burner. I think they both worked."
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