that most men over the age of twenty-five are unable to hear noises at 17.4 kHz or higher, which led to the invention of an alarm in the U.K. specially targeted at young people. It’s called the Mosquito. It blares out a horrifying whine at 17.4 kHz precisely, and can be cranked higher than 100 decibels, so that shopkeepers can use it to disperse loitering groups.
