In what could be the most frustratingly ingenious application of teenage subterfuge to date, the Beep app was built to let youth communicate without their parents or teachers noticing. The application sets a smart phone to send notices — such as those for an incoming call or text message — at a frequency of 14, hz. As people age, the upper range of their hearing diminishes. The frequency Beep uses falls in a range that most teens can still hear, but most adults cannot.
As year-old Eddie Holder sprinted from his apartment for school one recent morning, he held his hand to one ear to block out a shrill, piercing noise. The sound was coming from a wall-mounted box, but not everyone can hear it. The device, called the Mosquito , is audible only to teens and young adults and was installed outside the building to drive away loiterers. The gadget made its debut in the United States last year after infuriating civil liberties groups when it was first sold overseas. Already, almost 1, units have been sold in the U. It's this screeching sound that you have to get away from, or it will drive you crazy. The high-frequency sound has been likened to fingernails dragged across a chalkboard or a pesky mosquito buzzing in your ear.