High school students can download to their cellular phones ultra high-frequency ring tones that are inaudible to most of their teachers.

---Robert Dobie, MD, University of California, Davis

No wonder I never hear my cell phone when it rings in my purse. Not that it rings much, but that darling little trill of a tone just doesn't register on my aging ears on the rare occasions when someone calls.

Dr. Dobie notes that loss of ability to hear sounds of the highest frequencies begins in early adulthood and accelerates with age. Ultimately, lower, conversational frequencies start to drop out as well, so then the teenagers can actually answer their ringing phones in classes taught by 70-something substitute teachers.