Some people hear a high-pitched buzzing sound. Others describe it as a ringing, roaring, hissing, chirping, whooshing or wheezing. It can be high or low, single or multi-toned, an occasional mild annoyance or a constant personal din.

Tinnitus—whose Latin root means "to jingle"—is defined as the perception of sound when no external sound is present. It usually accompanies hearing loss, and while no one knows for sure what causes it, many experts believe that when people lose the ability to hear in certain frequencies, the...