[Rio]

devices that emit a high-frequency tone. .. generally only be heard by those under the age of 25

Where can I get one???

[fungoking]

devices that emit a high-frequency tone. .. generally only be heard by those under the age of 25
Where can I get one???

It's called The Mosquito, it emits a high pitched sound that adults can't hear. I'd play an extremely loud sample to my AP Psych students, I couldn't hear it but they would cover their ears. Business use it to keep teens from loitering.

I've found that classical music works well on most teens, country music works on skateboarders.

I had students use it as a ring tone. I couldn't hear it, but other students would complain about the noise.

http://www.freemosquitoringtones.org/the-mosquito/

[lefty-lie-spy]

You can download any number of frequency generators for your iPhone to test with, then search for “mosquito device loitering” and you will find the companies that manufacture such equipment.