Some Students Are Using A High-Frequency Ring Tone In Class
(AP) Students are using a new ring tone to receive messages in class — and many teachers can't even hear the ring.
Some students are downloading a ring tone off the Internet that is too high-pitched to be heard by most adults. With it, high schoolers can receive text message alerts on their cell phones without the teacher knowing.
As people age, many develop what's known as aging ear — a loss of the ability to hear higher-frequency sounds.
http://www.cbsnews.com/stories/2006/06/12/tech/main1701359.shtml