This has got to be the dumbest idea I've ever heard of - a ringtone at a frequency that older people can't hear:

In settings where cellphone use is forbidden -- in class, for example -- it is perfect for signaling the arrival of a text message without being detected by an elder of the species.

"When I heard about it I didn't believe it at first," said Donna Lewis, a technology teacher at the Trinity School in Manhattan. "But one of the kids gave me a copy, and I sent it to a colleague. She played it for her first graders. All of them could hear it, and neither she nor I could."

Well, except for the dead give-away - the head swivel by all the other students in class. I guess neither the Times nor these students have heard of silent vibrate modes?