What is Tinnitus?

Tinnitus (pronounced /tɪˈnaɪtəs/ or /ˈtɪnɪtəs/ from the Latin word tinnītus meaning "ringing") is the perception of sound within the human ear in the absence of corresponding external sound.
Tinnitus is not a disease, but a symptom resulting from a range of underlying causes that can include: ear infections, foreign objects or wax in the ear, nose allergies that prevent (or induce) fluid drain, and wax build-up. Withdrawal from a benzodiazepine addiction may cause Tinnitus as well.
Tinnitus can also be caused by natural hearing impairment (as in aging), as a side effect of some medications, and as a side effect of genetic (congenital) hearing loss. However, the most common cause for tinnitus is noise-induced hearing loss.
As tinnitus is usually a subjective phenomenon, it is difficult to measure using objective tests, such as by comparison with noise of known frequency and intensity, as in an audiometric test. The condition is often rated clinically on a simple scale from "slight" to "catastrophic" according to the practical difficulties it imposes, such as interference with sleep, quiet activities, and normal daily activities.
Tinnitus is common. About one in five people between 55 and 65 years old report tinnitus symptoms on a general health questionnaire and 11.8% on more detailed tinnitus-specific questionnaires.
Surce: wikipedia.org