DARPA's "Wall of Sound" Extinguishes Fires Using Just Noise
Okay, so you've extinguished a candle by blowing on it, or maybe pinching out the flame with your fingertips. But have you ever tried extinguishing it by humming at it? That's sort of what this machine devices by DARPA researchers does.
Wired writes, "The team arranged two speakers either side of a liquid fuel flame to demonstrate how fire can be controlled by amping up an acoustic field. The sound increases air velocity, which then thins the area of the flame where combustion occurs, known as the flame boundary. Once the boundary area is thinned, the flame is easier to extinguish. At the same time, the acoustics are disturbing the pool of fuel and creating higher fuel vaporisation — this widens the flame, thinning it out so it is less concentrated and cool enough to extinguish."
The sound doesn't have to be all that loud to accomplish the goal, which is good considering the tool would be used in enclosed spaces like on aircrafts and ships. Unfortunately, it wouldn't be much good for all those wildfires we've been seeing, and can expect more of as things heat up. But it is an interesting way to use something as simple as sound, rather than water or chemicals to extinguish flames.