Tinnitus is defined as the perception of sound in one or both ears or in the head when no external sound is present. It is often called "ringing in the ears," although some people hear hissing, roaring, whistling, chirping or clicking.Though statistics vary, according to the American

Tinnitus Association, more than 50 million Americans experience tinnitus to some degree. Of these, about 12 million people have tinnitus severe enough to seek medical attention. About 2 million people are so debilitated by the noise that they can't function on a day-to-day basis.According to the American Academy of Otolaryngology, Head and Neck Surgery, most tinnitus comes from damage to the microscopic endings of the hearing nerve in the inner ear. In older people with tinnitus, the tinnitus could result from hearing nerve impairment that often comes with advancing age. In younger people, the leading cause of tinnitus is exposure to loud noise.