I can't say I have fail-proof advice for any storekeeper confronted with a pack of noisy (or even dangerous) teenagers congregating outside his door. Calling the police doesn't always work for long. Changing social mores isn't what you'd call a quick fix. Nicely asking them to loiter elsewhere...? Er, no. Still, there's plenty that's disturbing about the "mosquito" solution:

In Britain, adolescents are the new mosquitoes. Many storekeepers and municipalities now employ ultrasonic devices, of the kind hitherto used to scatter insects and rodents, to disperse young people wherever they habitually gather to make a nuisance of themselves.

The so-called "mosquito" devices--there are some 3,500 installed throughout the country--take advantage of the fact that only people younger than 20 can perceive and be discomfited by the high-pitched sounds the devices make, discouraging them from lingering in the vicinity.

Now, the owners of a building in Queens are fitting it with just such a youth repellent. No doubt other buildings will soon follow suit.

It is an easy answer to a difficult problem. Those adults should turn back now--lest they turn New York into a city that is chronically afraid of its young people.

Yeah, no doubt treating youths like cockroaches will encourage them to behave. How could it not? The author also wonders whether teenagers will eventually get used to the sound, as their eardrums are dulled by loud music and the like. It sounds curmudgeonly, but I can attest. My hearing is pretty dismal (mostly I blame Steve Albini) and I could never pick out high-pitched whines of any sort. And why are adolescent eardrums so sensitive, anyway? What changes when you turn 20?