While most human communication takes place in a frequency range between 200 and 8,000 hertz (a hertz being the scientific unit of frequency equal to one cycle per second), most adults' ability to hear frequencies higher than that begins to deteriorate in early middle age.

"It's the most common sensory abnormality in the world," said Dr. Rick A. Friedman, an ear surgeon and research scientist at the House Ear Institute in Los Angeles.

But in a bit of techno-jujitsu, someone — a person unknown at this time, but probably not someone with presbycusis — realized that the Mosquito, which uses this common adult abnormality to adults' advantage, could be turned against them.

The Mosquito noise was reinvented as a ring tone.

"Our high-frequency buzzer was copied. It is not exactly what we developed, but it's a pretty good imitation," said Simon Morris, marketing director for Compound Security, the company behind the Mosquito. "You've got to give the kids credit for ingenuity."

British newspapers described the first use of the high-frequency ring tone last month in some schools in Wales, where Compound Security's Mosquito device was introduced as a "yob-buster," a reference to the hooligans it was meant to disperse.

Since then, Morris said his company has received so much attention — none of it profit-making, because the ring tone was, in effect, pirated — that he and his partner, Howard Stapleton, the inventor, decided to start selling a ring tone of their own. It is called Mosquitotone, and it is now advertised as "the authentic Mosquito ring tone."

David Herzka, a Roslyn High School freshman, said he researched the British phenomenon a few weeks ago on the Web and managed to upload a version of the high-pitched sound into his cell.

He transferred the ring tone to the cell phones of two of his friends at a birthday party on June 3. Two days later, he said, about five students at school were using it, and by June 6 the number was a couple of dozen.

"I just made it for my friends. I don't use a cell phone during class at school," he said.

How, David was asked, did he think this new device would alter the balance of power between adults and teenagers? Or did he suppose it was a passing fad?

"Well, probably it is," said David, who added after a moment's thought, "And if not, I guess the school will just have to hire a lot of young teachers."

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Contributing: Kate Hammer and Nate Schweber