Q: Why can I cancel out the hissing noise of my gas fire by aiming an old-style ultrasonic TV remote control at it?
A: The effects of sounds on naked gas flames appears to have been first noticed by Professor Leconte at a musical party in the US in 1858. Professor Tyndale gave an evening discourse on sounding and sensitive flames at the Royal Institution in 1867. This ended with a gas flame curtsying to the notes of a music box.
In 1966, Frank Briffa and I observed that a small amount of ultrasonic energy directed across an orifice would reduce the noise from a gas jet, lit or unlit (this now forms British Patent 1 147 103). This was demonstrated in the library of the Royal Institution a century after Tyndale鈥檚 presentation.
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Acoustic waves that are directed across the top of a jet orifice cause disturbances in the gas flow which grow to form vortices. These are shed downstream from the nozzle on either side of the jet. This gives a broader and more stable flame, which emits less noise. Only a small amount of ultrasonic energy is required, a transducer using less than 0.01 per cent of the energy produced by the flame gave a noise reduction of 5 dB(A). An account with Schlieren photographs of the gas jets with and without the ultrasonic field was published in New 杏吧原创 (鈥淢ore sound means a quieter flame鈥�, 18 June 1970).
Although our work at the Egham Laboratories of Shell Research was mainly involved with reducing noise from large industrial burners, there was general concern at the time that domestic gas fires, being converted from town gas to natural gas were much noisier after the conversion. We found that this could be eliminated by the combination of a small ultrasonic source and a tapering of the gas nozzles. However, people soon got used to the extra noise of natural gas.
At one time there was even press speculation that ultrasonics could be applied to aircraft engines. So do not ditch your old ultrasonic remote controls.