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Registered Member #1526
Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216
Ha, I was just looking over the research project options for my final year and came across this gem:
-------------------------
Project Title: Thermophone Project Description: The phenomenon of sound is due to longitudinal pressure waves in a fluid. The most common way of converting an electrical signal into sound waves is to use a loudspeaker, essentially an electrically operated piston that alternately compresses and rarefies the air. Another method of producing sound waves is by alternately heating and cooling the air. A thunderclap is a well-known example of sound produced by rapid heating of air by lightening. The idea of the thermophone is to exploit this heating method to convert an electrical signal into sound. There has been very little previous work on thermophones. Two papers can be found on the web by typing 'thermophone' into a search engine. The aim of this project is to develop a prototype thermophone using techniques and materials available in the lab. It does not need to be high-fidelity, but it should be audible by the unaided ear.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
Thermal expansion/contraction is the predominant cause of sound creation by a plasma speaker (in theory ion wind could play a part, but not with the HF modulated methods popular here).
I wonder if you couldn't do this much more efficiently by flash vaporizing a low boiling point (or just take water at reduced pressure) liquid as a medium to heat in very small areas. I'm thinking of a big array of small bits (<< 1mm) of nichrome wire. These would then form bubbles in the same way as in inkjet printers (which would rapidly collapse as the power is turned off as the surrounding liquid cools them back down, inkjet heads can work at many kHz).
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Fraggle wrote ...
I`ll start working through that paper. It has a wealth of juicy-looking references too, thanks.
It has the feel of something that was intended for a journal, but isn't in one (yet?), so be cautious around any contentious-looking statements.*
But it seems useful as a survey of the thermophone terrain, with juicy references to boot!
*EDIT: Woops! I got that one wrong! The paper appears in Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2010 12th IEEE Intersociety Conference on Date: 2-5 June 2010 pp 1-5, but has changed its name from Thermophones and quantum mechanics to Thermophones by quantum mechanics
Registered Member #1526
Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216
Well, no thermophone for me but I did get something good - we have to design an ultra low noise ~10MHz signal amplifier to be operated at 4K. It will sit in a cryostat amplifying the signal from a micromechanical oscillator thingy in there with it. We get to characterise a transistor at 4K and then analyse the performance of whatever we build at 4K too!
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Final year lab project
