How to extinguish a fire by blasting sound

Sandrine Ceurstemont, editor, New Scientist TV

Forget blasting out your favourite tunes: you could now use speakers to put out a fire. A new video from the US Defense Advanced Research Projects Agency (DARPA) shows how to extinguish burning fuel by trapping it in an acoustic field generated by surrounding speakers.

By using specific frequencies, a fire is killed in a two-pronged attack. First, sound increases the air speed, thinning the layer where combustion occurs and thus making it easier to disrupt the flame. But the acoustics also disturb the surface of the fuel which increases vaporisation, widening the flame and cooling its overall temperature.

Whereas typical firefighting techniques disrupt chemical reactions involved in combustion, DARPA has been looking at approaches like this one that exploit physics. Previously, they've used an electric field to blow out a flame by creating an ionic wind. They hope to develop these alternatives to help put out fires in military environments, for example in confined spaces, like cockpits and ship holds.

If you enjoyed this post, watch a knitted suit resist 1000 ?C flames or see how to fight a fire in space.

Source: http://feeds.newscientist.com/c/749/f/10897/s/21644194/l/0L0Snewscientist0N0Cblogs0Cnstv0C20A120C0A70Chow0Eto0Eextinguish0Ea0Efire0Eby0Eblasting0Esound0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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