George Mason University engineering students Seth Robertson and Viet Tran encountered plenty of doubters when they settled on an idea for their senior project. Even the typically experimental thinkers of academia thought a fire extinguisher that puts out flames with sound waves was outrageous. And in a sense, they were right. Robertson and Tran did invent something outrageous. But they also invented something that works.
Here’s how: By blasting a flame with low-frequency sound waves in the 30 to 60 hertz range, the extinguisher separates oxygen from 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 told the Washington Post.
Robertson and Tran envision their technology being used to put out fires in homes — and in the wild. If properly scaled, sound-wave extinguishers would eliminate the need to douse forests in chemicals or waste untold gallons of water. But that’s still a long way away. So far, the extinguisher has only put out fires that use rubbing alcohol as fuel. Proving the ability to extinguish real-life fires, like those that involve fabric, wood, or cooking oil, is the team's next step.
If nothing else, their invention is a step toward modernizing fire-fighting, a goal DARPA began working toward in 2008. In 2012, the military’s experimental research lab presented a video of its own fire-suppressing sound waves, but the bulky, impractical setup would only put out a fire if it was set between two booming speakers. Unlike the design Robertson and Tran are toying with, it's hard to imagine that working in a kitchen.