Tinnitus is the perception of sound in the absence of corresponding external sound(s). Tinnitus can be perceived in one or both ears or in the head. It is usually described as an unpleasant noise, but in some patients it takes the form of a ringing, buzzing, hissing, humming, or whistling sound, or as ticking, clicking, roaring, tunes, songs, or beeping. It is estimated that 1 out of every 5 people experience some degree of tinnitus. Tinnitus is not itself a disease but an unwelcome symptom. It can be accompanied by audiometric evidence of deafness which occurs in association with both conductive and sensorineural hearing loss resulting from a range of underlying causes, including ear infections, foreign objects orwax in the ear, and injury from loud noises. Tinnitus is also a side-effect of some metabolic disorders, medications, and may also result from an abnormally low level of serotonin or high level of insulin. As mentioned above, some foods are found by some people to make their tinnitus worse. The inner ear, like the brain, is totally lacking in energy reserves. Its metabolism depends directly on the supply of oxygen and glucose from the blood supply. Alterations in glucose metabolism therefore have great potential for disturbing the workings of the inner ear. Because tinnitus is often defined as a subjective phenomenon, it is difficult to measure using objective tests. Although there is no specific cure for tinnitus, those affected can learn techniques to successfully manage their tinnitus to the point where it is no longer a problem for them.