A most curious use of sound:

Shopkeepers in central England have been trying out a new device that emits an uncomfortable high-pitched noise designed to disperse young loiterers outside their stores without bothering adults.

Police carrying out the pilot project in Staffordshire say some of those who have tested the "Sonic Teenager Deterrent," nicknamed the mosquito, have talked of buying one of their own.

The device which costs 622 pounds (908 euros, 1,081 dollars) "doesn't cause any pain to the hearer," according to Inspector Amanda Davies, quoted by Britain's domestic Press Association news agency.

"The noise can normally only be heard by those between 12 and 22 and it makes the listener feel uncomfortable," she added.

Once in their early 20s, people lose their capacity to hear sounds at such a high pitc

We will not be purchasing one. We would like our teens to stick around (at least so far).