Extinguishing fire with sound

Researchers from the Defense Advanced Research Projects Agency (DARPA), in the USA, report on new ways to extinguish fire. "Traditional fire-suppression technologies focus largely on disrupting the chemical reactions involved in combustion. However, from a physics perspective, flames are cold plasmas." DARPA theorized that by using physics techniques rather than combustion chemistry, it might be possible to manipulate and extinguish flames, according to a July 12 news release on their website. 

Their findings show that fire can be suppressed using sound and electromagnetism. In one of their experiments involving sound, scientists used two speakers placed on either side of an open liquid fuel flame. The acoustic field emitted was sufficient to control the fire. "The sound increases air velocity, which then thins the area of the flame where combustion occurs, known as the flame boundary." 

DARPA has a fame for making some rather unusual inventions, such as hypersonic unnamed rockets, bionic prosthetic limbs and insect-sized reconnaissance drones. Matthew Goodman, DARPA program manager, said, "We have shown that the physics of combustion still has surprises in store for us." 

Now, the agency will try to translate this new invention into some practical invention that will benefit us all.