Tinnitus is the perception of sound without external acoustic stimulation. The sound is intermittent, fluctuating or - in most cases - constant, may be perceived as ringing ("tinnire" is the Latin word for "to ring"), roaring, hissing or some other noise, and is usually high-pitched. Tinnitus can occur in one ear or both ears and is considered acute up to 3 months from onset and chronic if persisting longer. Tinnitus has been affecting people since ancient times - descriptions of the disorder were already found on Babylonian clay tablets.
Most people will experience a transient tinnitus (less than five minutes long) or mild tinnitus that may not compel them to seek medical evaluation. However, some people have more annoying and persistent types of tinnitus. Similar to pain, tinnitus is an unwanted, unpleasant sensation and may seriously impact the ability to sleep, relax or to concentrate, or lead to tiredness and nervousness and affect normal day-to-day activities. According to some estimates, 0.3 to 1% of the population may suffer from tinnitus in a way that they are prevented from leading a normal life.
Tinnitus can be triggered by a variety of diseases or events such as noise trauma, infection, inflammation, disrupted blood supply, jaw joint problems, head trauma or whiplash injury. Sometimes its origin is simply unknown. The precise mechanisms of tinnitus generation are still the subject of considerable debate and remain to be fully elucidated. In the vast majority of cases, tinnitus is associated with hearing loss of known origin, and probably more than two thirds of all cases originate within the cochlea.