Tinnitus is a condition commonly known as "ringing in the ears". The ringing sounds are brain-induced; that is, ringing is perceived in the absence of any external auditory stimulation. In addition to ringing sounds, roaring, hissing, clicking and other non-externally generated sounds are also tinnitus sounds. Chronic tinnitus can be caused by noise exposure, disease, excessive use of aspirin or other pain relievers, and use of certain antibiotics.

According to the American Tinnitus Association (ATA) it is estimated that approximately 50 million persons in the U.S. have intermittent or permanent tinnitus. Of these, approximately 10-12 million have severe and chronic tinnitus. The ATA reports that of these some two million persons are completely disabled by the condition. Severe tinnitus in some drastic cases has led to suicide.

Unfortunately, many armed forces personnel serving overseas are subjected to noise environments that can directly lead to tinnitus even when these personnel use earplugs. To make the problem worse, some of these service personnel are averse to using such protective devices when in harm's way - potentially to their own detriment. Excessive noise exposure from firing weapons, and exposure to ordinance and IED's can initiate life-long tinnitus. In the worst case of serious traumatic brain injury as a consequence of explosive IED's, tinnitus may also accompany the primary injury and negatively impact recovery.

For the general population, tinnitus is also associated with listening to music players with earbuds (i.e. i-pods) at elevated volume levels for extended periods of time. An increased incidence of tinnitus is also observed in the elderly.