A pair of graduating engineering students at George Mason University has invented a new device that can put out fires using sound waves.
That's right. No water, no foam. Only a deep, bass rumble that is similar to the thud-thumping you hear in hip hop and rap songs.
Electrical engineering major Seth Robertson teamed up with computer engineering student Viet Tran to develop a new device that could potentially revolutionize the firefighting industry. The device was borne out of a senior research project that took a year of trial-and-error and their own money amounting to $600 to test and complete.
The result is a 20-kilogram device that uses low-frequency sound waves in the range of 30 to 60 hertz that can effectively put out a fire. At first, that was not what the students had in mind. They tried placing a pan filled with a fire fueled by rubbing alcohol next to a subwoofer blaring out music, but nothing happened as they realized the frequencies in music are inconsistent.
Then they tried experimenting with ultra-high frequencies ranging from 20,000 to 30,000 hertz, but all the sound waves did was get the flames vibrating. The sweet spot, they discovered, is in the low range of 30 to 60 hertz, where the sound waves, which the students say are also pressure waves, can keep the oxygen away from the flame long enough to eventually put out the flame.
To set up the device, the students rolled a cardboard cylinder and cut out a large hole at one end to serve as the collimator, or the device that narrows the sound waves down to a single direction. They connected the collimator to a frequency generator, a small amplifier, and a power source, and the result is a fire extinguisher that uses sound waves instead of water or toxic chemicals.
As Tran tells the Washington Post, the low-frequency sound waves "separate the oxygen [which keeps the fire burning] 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." In other words, as the sound waves move through the air, they displace the oxygen that feeds the flame, thus extinguishing the fire.
"I honestly didn't think it would work as well as it did," Tran says.
The students initially intended their invention for putting out small kitchen fires, but officials at a fire department have already volunteered to test it in putting out larger building fires. Eventually, the students believe the device can be used for other purposes, such as in extinguishing fires in large confined spaces or wider open areas, such as forest fires.
However, they say they still need to do a lot more testing to see if their device can put out fires from different combustibles, such as wood, paper, metal, or electric wires.
The project was inspired by a 2012 Defense Advanced Research Projects Agency (DARPA) project that successfully put out a fire using a large machine that generated sound. However, DARPA admitted it could not find a practical purpose for the project because of the bulky equipment, a fact that the students capitalized on to develop something that could eventually get to market.
Check out the video shown for a demonstration of how sound waves can effectively put out an alcohol-fueled fire.