Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone will experience a faint "normal tinnitus" in a completely quiet room but it is only of concern if it is bothersome or interferes with normal hearing or correlated with other problems. While often described as a ringing, it may also sound like a clicking, buzzing, hiss, or roaring. The sound may be soft or loud, low or high pitched, and often appears to be coming from one or both ears or from the head itself. In some people, the sound may interfere with concentration and in some cases it is associated with anxiety and depression. Tinnitus is usually associated with a degree of hearing loss and with decreased comprehension of speech in noisy environments. It is common, affecting about 10–15% of people. Most, however, tolerate it well, and it is a significant problem in only 1–2% of all people. It can trigger a fight-or-flight response, as the brain may perceive it as dangerous and important. The word tinnitus comes from the Latin tinnire which means "to ring".Rather than a disease, tinnitus is a symptom that may result from various underlying causes and may be generated at any level of the auditory system and structures beyond that system. The most common causes are hearing damage, noise-induced hearing loss or age-related hearing loss, known as presbycusis.
In most cases, tinnitus pitch or frequency range is between 5 kHz and 10 kHz, and loudness between 5 and 15 dB above the hearing threshold.Another relevant parameter of tinnitus is residual inhibition, the temporary suppression or disappearance of tinnitus following a period of masking. The degree of residual inhibition may indicate how effective tinnitus maskers would be as a treatment modality.An assessment of hyperacusis, a frequent accompaniment of tinnitus, may also be made. Hyperacusis is related to negative reactions to sound and can take many forms. One associated parameter that can be measured is Loudness Discomfort Level (LDL) in dB, the subjective level of acute discomfort at specified frequencies over the frequency range of hearing. This defines a dynamic range between the hearing threshold at that frequency and the loudness discomfort level. A compressed dynamic range over a particular frequency range can be associated with hyperacusis. Normal hearing threshold is generally defined as 0–20 decibels (dB). Normal loudness discomfort levels are 85–90+ dB, with some authorities citing 100 dB. A dynamic range of 55 dB or less is indicative of hyperacusis. Severity
The condition is often rated on a scale from "slight" to "severe" according to the effects it has, such as interference with sleep, quiet activities and normal daily activities.Assessment of psychological processes related to tinnitus involves measurement of tinnitus severity and distress (i.e., nature and extent of tinnitus-related problems), measured subjectively by validated self-report tinnitus questionnaires.