Tinnitus[1] is defined as a condition during which a person hears sound that isn’t caused by an external source. The sound most people with tinnitus describe is a steady, high-pitched ringing, but the sound has also been described as continuous or intermittent whistling, static, whooshing, musical noise, or buzzing. Approximately 1 in 10 adults[2] in the U.S. experienced at least one bout of tinnitus over the course of a year, with just over a third of those reporting chronic problems. If tinnitus is persistent and intolerable or extremely bothersome, it can cause functional impairment[3] in thought processing, emotional state, hearing, sleep, and concentration.
There are two general types of tinnitus. Objective tinnitus (about 5% of cases) refers to sounds that are able to be heard with external instruments, such as a stethoscope. This type of tinnitus is usually caused by damage to the bones or vasculature of the ear. Subjective tinnitus (about 95% of cases) refers to sounds that cannot be heard from the outside and is thought to be caused by damage to the neuronal system of the ear. Figure 1 provides more detail about the differences between these types.
