Did you hear something?

In the latest example of how technology's rapid evolution has created new challenges for educators, some students are downloading a cell phone ring tone that is too high-pitched for most adults to hear.
Originally marketed to prevent unwanted gatherings of youths and teenagers in shopping malls and around shops or chase them away, Compound Security's Mosquito device emits a high-pitched sound, like a constant insect buzzing, to drive loitering teens away. Not only shopkeepers, Railway companies have placed the device to discourage youths from spraying graffiti on trains and the walls of railway stations.
While most human communication takes place in a frequency range between 200 and 8,000 hertz, most adults' ability to hear frequencies higher than that begins to deteriorate in early middle age. The company wasn't making any money off the ringtone because it was pirated, so the inventors started selling a ring tone of their own.
It is called Mosquitotone and has now become the secret ringtone that teens are using to get calls and text messages in class or other places where their phones are officially supposed to be OFF.
Download Mosquito Ringtone
BBC Radio Swindon feature