Can you hear me now?

Teenagers are using high pitched ringtones to communicate and their elderly teachers (10+ years older) supposedly can't hear them. Here is what you can do to get back at teenagers:
Frequency test your ears and find the highest pitch you can hear. Now kick it up a notch (so you can't hear it), record it on loop and play it back continuously. You won't hear a thing but your teenager will likely go crazy because of the noises in their head.

Woot!