There are sound frequencies that only young people can hear. This ear-aging process is called presbycusis, and it can begin as early as This means you are alive. Most people over 18 should not be able to detect this sound. Some major retailers actually use this science to keep teens from loitering outside their stores. Pretty brilliant!

Several young students have caught on to a recent trend: a ring tone that only they can hear and most adults can't. Dubbed the Mosquito, the noise stems from an antitheft technique in the United Kingdom, where it was used to deter youth crimes such as shoplifting. The idea is that most adults lose the ability to hear high-pitched sounds as they grow older, so this tone will reach the ears of only the young. Some enterprising unknown must have then copied this high-pitched tone and made it into a ring tone, which was then distributed to students in the United Kingdom and spread around on the Internet until it eventually reached U.

Think you have perfect hearing? The low range of human hearing starts around 20 hertz, and tops out at about 20, [ PDF ]. By contrast, bats can hear ultrasonic sounds with frequencies up to , hertz.

Introduction Ever wonder why some adults experience trouble with hearing as they get older? Hearing loss tends to become more severe as we age. But does hearing loss cause everything to sound uniformly softer or do certain sounds become harder to hear than others? Some security companies recently began manufacturing machines designed to emit an annoying sound that prevents teenagers from loitering outside stores and shops.