Two students of George Mason University in Fairfax, Virginia, have developed a handheld fire extinguisher that uses low-frequency sound waves. The technology is based on the ability of sound waves to displace oxygen through physical space. Starve flames of their favorite fuel and you can extinguish them. The device was successfully tested on small, controlled fires, and more work is needed to make it a reliable alternative to water and foam. A promising technology for areas where water supplies are dwindling.