Turn Up the Bass! Engineering Students Invent a Sound-Wave Fire Extinguisher

Two engineering students from George Mason University in Virginia have come up with an invention that could revolutionize firefighting technology. Viet Tran and Seth Robertson propose to use sound waves to stop fires, as the previous research has shown that sound has the ability to affect fire. So far, there are no fire extinguishers based on a similar principle.

In fact, the idea of fighting fires with sound is not new. The Darpa (Defense Advanced Research Projects Agency) has conducted a number of experiments on suppressing fire with an acoustic field. However, the results did not lead to the development of a practical device that could be utilized to extinguish fires in everyday situations.

Having focused on the impact of sound waves on fire during their senior research project, the two students started with the idea that sound is a mechanical wave that can affect objects. They thought that if the burning material and the oxygen around it got separated by sound waves, the reaction between these two would stop and the fire would go out.

The waves “separate the oxygen [in the fire] from the fuel. The pressure wave is going back and forth, and that agitates where the air is. That specific space is enough to keep the fire from reigniting,” Tran said.

After a number of experiments, during which Tran and Robertson used sound frequencies of different ranges, it was found that low frequencies between 30 and 60 Hertz were the most effective in fighting fires. Thus, the students decided to build a portable device that would focus the sound waves at a fire and came up with a small fire extinguisher consisting of a sound generator, an amplifier, a power source and a cardboard focusing tube.

It doesn’t require any chemicals or water, which is one of the main advantages of this technology, and thus provides a much simpler and cleaner way to fight fires. Till now, the sound based extinguisher has been tested only on small alcohol flames, but the inventors hope to improve the technology to be used for a wider range of applications. For example, a similar device could be mounted in kitchen hoods to quickly stop small fires or utilized by astronauts to extinguish fires on space stations.

“In space, extinguisher contents spread all over. But you can direct sound waves without gravity,” Robertson said.

Of course, there are still some technical issues to overcome before the innovative extinguisher can be used in real life. The main problem is that the sound waves do not cool the fuel, which makes it difficult to use the device on big fires.

“We still want to do a lot more testing to see if we need to change the frequency [to extinguish] other” materials, before plunking down thousands of dollars to apply for a patent,” Tran concluded.