During the day, playgrounds welcome young people to come and play. But at night, one particular playground is using the power of sound to sending teens scurrying for cover.
Fearing vandalism and late night loitering, a Parks & Recreation department in Northeastern Philadelphia has installed The Mosquito — a device which makes an annoying, high-pitched noise primarily perceptible only to teenage ears — to drive away young people.
See how it works – and test your own pitch perception HERE
