tinnitus

The perception of sound that has no external source, so other people cannot hear it. It is usually described as ringing, but also as roaring, buzzing, hissing or clicking, and it can be constant or come and go.

It is common: an estimated 10 to 25% of adults have it. Known causes include noise exposure, hearing loss, some medications, earwax blockage or ear infections, and head or neck injuries. Less often it comes from Ménière's disease, jaw problems, tumours, blood-vessel problems, or conditions such as diabetes and thyroid disorders. Some people develop it for no known reason.

Related terms: presbycusis, phantom sensations, microwave auditory effect

Sources: What Is Tinnitus? — National Institute on Deafness and Other Communication Disorders (NIH)