Device for high-frequency sounds to prevent loitering by teenagers (movingsoundtech.com)

I enjoyed scrolling to the bottom to listen to the different sounds the device can produce. The disclosed age/frequency pairs seem remarkably accurate and, of course, the sound is quite annoying.

This device is not without controversy:

http://www.bbc.co.uk/news/10412057

http://en.wikipedia.org/wiki/The_Mosquito#Opposition

http://en.wikipedia.org/wiki/The_Mosquito#Legal_status

http://www.liberty-human-rights.org.uk/issues/young-peoples-...

http://www.dailymail.co.uk/news/article-513822/Buzz-Outcry-C...

My local library solved this problem by blasting three different operas at obnoxious levels just outside the doorways.

It works, but it makes me cringe every time I walk into the library.