You may be familiar with the concept of mall rats: suburban kids who hang around malls but don't do much shopping? Kevin Smith made a movie about them about 15 years ago. Anyway, some people consider them a nuisance and in response, a British company called Compound Security Systems has created a device called the mosquito. The Mosquito works by exploiting presbycusis, otherwise known as age-related hearing loss. Basically, people over 20 can't hear sounds between 18 kHz and 20 kHz, so the Mosquito emits a loud tone between those two frequencies that eventually (after 8 to 10 minutes, according to Compound Security Systems tests) drive away anyone who can hear them. Interesting idea to drive away the anti-social mall rats, but I guess it wouldn't work so well if you own a pet store.

Via The Bexley Times