Dig this: A Welsh inventor has created a device intended to shoo teenagers from hanging out near your house or store -- by emitting an annoying sound so high-pitched that adults cannot hear it. The inventor, Howard Stapleton, got the idea by recalling a time when he was 12 and visited a factory with his father; the sound of high-frequency welding equipment totally annoyed him, but his father couldn't perceive it. This, he later realized, is because of a physiological quirk of aging: Children can hear higher frequencies than adults.

Stapleton began experimenting, trying to find the acoustic sweet spot -- the precise frequency that will annoy the heck outta the kidz yet remain undetected by the middle-aged. There's a terrific story in today's New York Times about it:

Using his children as guinea pigs, he tried a number of different noise and frequency levels, testing a single-toned unit before settling on a pulsating tone which, he said, is more unbearable, and which can be broadcast at 75 decibels, within government auditory-safety limits. "I didn't want to make it hurt," Mr. Stapleton said. "It just has to nag at them."

Apparently the noise sounds like "pulsating chirp" reminiscent of tinnitus. The Mosquito has only been tested in one convenience store in South Wales, but hey presto, as soon as it was turned on the teenagers fled.

As for the science behind all this? It's certainly true that hearing sensitivity declines with aging -- the technical term is presbycusis -- but it's hardly a linear process. The danger is that many older folks could hear the noise (indeed, one 34-year-old who visited the convenience store could). But the overall concept is pretty hilarious. That's a picture of Stapleton above, by the way, from the Times story.