Source: Slashdot | Driving Away Teens With High Frequency Noise
"The New York Times is reporting on a device called the Mosquito invented by Howard Stapleton designed to drive teens away by emitting a high frequency noise at 75db. Apparently most older people can not hear the sounds, but teens can not stand it. Reports are that it works quite well, but some older people can hear it too. He found the prefect irritating sound by experimenting on his children."