Here's an interesting idea, create a machine that emits a high-frequency pulsing sound that can be heard by most people younger than 20 and almost no one older than 30. The sound is designed to so irritate young people that after several minutes, they cannot stand it and go away. The result was:
At first, members of the usual teen crowd tried to gather as normal, repeatedly going inside the store with their fingers in their ears and "begging me to turn it off," Mr. Gough said. But he held firm and neatly avoided possible aggressive confrontations: "I told them it was to keep birds away because of the bird flu epidemic."
"It's loud and squeaky and it just goes through you," said Jodie Evans, 15, who was shopping at the store even though she was supposed to be in school. "It gets inside you."
I'm looking for reasons to look forward to my 30th B'day :)

