The thumping bass lines that go along with rap songs may annoy some uninterested listeners, but such low noises can be used to put out fires.
Two engineering students have built a handheld device that uses sound to extinguish flames—and the breakthrough could one day revolutionize firefighting. It works because the low frequency noise, which compares to the “thump” of hip-hop music, separates oxygen from fuel to stop a fire from burning.
The 20lb (9kg) device, was created by engineering students Seth Robertson and Viet Tran from George Mason University. Initially, both students thought big speakers and high frequencies would put out a fire. “But it’s low-frequency sounds—like the thump-thump bass in hip-hop that works,” Mr Tran said. He joked that rappers like 50 Cent could probably douse a fire, explaining that low frequency sound waves between 30 and 60 Hertz work best.
When the device is used, humans with hearing between the typical range of 20 to 20,000Hz can hear the explosion of sound. “The pressure wave is going back and forth, and that moves where the air is,” Mr Tran told The Washington Post. “That specific space is enough to keep the fire from burning again.” In particular, the acoustic field(声场) created by sound increases the air velocity(速度) around a flame. As this velocity rises it thins what’s known as the flame’s “boundary layer”. And as it thins, it becomes easier to interrupt the burning process and ultimately put out the flame.
The two students were inspired to create their gadget(器具) after watching a video showing how two giant tubes of sound waves can put out fire. However, unlike the agency, the students managed to squeeze the idea into a portable device, which could possibly one day be used in place of a traditional fire extinguisher.
The new device has benefits such as being free of toxic chemicals and not subjecting buildings to water damage, for example.
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