Tinnitus is the perception of sound within the human ear in the absence of corresponding external sound.
Tinnitus is not a disease, but a condition that can result from a wide range of underlying causes: neurological damage (multiple sclerosis), ear infections, oxidative stress, foreign objects in the ear, nasal allergies that prevent (or induce) fluid drain, wax build-up and exposure to loud sounds. Withdrawal from benzodiazepines may cause tinnitus as well. In-ear earphones, whose sound enters directly into the ear canal without any opportunity to be deflected or absorbed elsewhere, are a common cause of tinnitus when volume is set beyond moderate levels.
Tinnitus may be an accompaniment of sensorineural hearing loss or congenital hearing loss, or it may be observed as a side effect of certain medications. However, the most common cause 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 20% of people between 55 and 65 years old report symptoms on a general health questionnaire, and 11.8% on more detailed tinnitus-specific questionnaires.