Putting out fire with bass

Print edition : May 01, 2015

Sound-blasting fire extinguisher prototypes invented by two students of George Mason University. Photo: Evan Cantwell/GMU

TWO final year engineering undergraduate students at George Mason University, U.S., Seth Robinson and Viet Tran, have invented a new type of fire extinguisher that uses low-frequency (bass) sound waves to put out fires. It is free of chemicals and water. The students hold a patent application for the device.

The concept of using sound waves to extinguish flames has been attempted in the past. The U.S. Defence Advanced Research Projects Agency, for instance, had tried earlier but failed. Undeterred by this and the scepticism of their peers and faculty, the two students began to explore the idea.

The underlying principle is simple: as sound waves are nothing but mechanical pressure waves that cause vibrations in the medium they travel in, they have, in principle, the potential to cause changes to burning material and the surrounding oxygen. The idea is to separate the combustible material and the oxygen so that the fire is put out. The two undergrads studied the impact of different frequencies of sound on small fires. While ultra-high frequencies had little effect, lower frequencies, between 30 and 60 Hz, seemed to have the desired effect. The device consists of an amplifier and a cardboard collimator to focus the sound. The prototype cost only about $600 to develop, weighs 9 kg and is a hand-held device that is powered by main electricity. The prototype has gone through many trials.

The researchers are now planning to test and refine the device with the aim of developing a commercial product. Although it was originally envisaged for applications to douse small fires, the two are now studying the possibility of wider applications, such as its applicability in space where conventional firefighters cannot be easily directed on the target. The invention could also lead to the development of applications against forest fires or urban blazes. The duo envisages a swarm of robotics with the device attached to a drone to be used in such situations.

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