Do you have unruly youths loitering around your shop or home? To make them disperse you have about three options:
You can yell at them to bugger off, which is a risky strategy, because they'll probably kick the crap out of you.
You could try The Mosquito, a machine that emits an annoying high pitched buzz that only whippersnappers can hear. But that's a tad controversial, since it's deemed an infringement of human rights by civil libertarians.
Instead, I would recommend the "Manilow Method". It's an effective teen repellant, and attracts much more polite and agreeable oldsters.