From the Chicago Tribune, April 2, 2008:

A sharp, pulsating, high-pitched tone burrows into the ear like a power drill bit, prompting an agitated, please-shut-that-blasted-thing-off grimace. That's what you hear if you're age 13 to 25.

If you're not, you may not sense a thing.

The device, called the Mosquito, was invented in Britain, where it has become the next big thing in crowd and crime control, chasing away young loiterers and ne'er-do-wells. It entered the U.S. market as a sort of "teen repellent" last fall. The device works because an age-related hearing loss called presbycusis reduces the ability to hear high-pitched sounds after the late 20s. The Mosquito's sound is mostly inaudible to older adults, young children and pets.

“We use the car device at sporting events, in the parking lot after the games where people start congregating and the problems start. We'll switch it, on and immediately you'll see heads turn. ... They become irritated from the noise, and within about five minutes, they've all gone somewhere else."

It’s not an unmixed blessing, though. The teens are using it to make ringtones that we old coots can’t hear.

Makes sense. Far-sightedness in the middle-aged and elderly is called presbyopia.

[By the way, Shu, please do not check the Bluffing Game. I made a fool of myself. ]

Now you know why I thought the right answer was yours!

quote:

middle-aged and elderly is called presbyopia

Also presbyter (elder) and Presbyterian.

Suspicious label, found behind a fraudulent bush: Presbydeception.