Most cases of tinnitus result from sensorineural or conductive hearing losses, and people with a history of noise exposure are more likely to experience tinnitus. In a minority of cases (10-15%) people with tinnitus have normal audiometric results; however, there is growing evidence that many in this group may in fact have a sensorineural hearing loss which is not picked up on in standard hearing tests. Some other less common potential causes of tinnitus, especially for those with normal audiometric results, include head injury and abnormal somatosensory activity.