Tinnitus refers to the perception of sound without an external source. It is often described as ringing, hissing, or whooshing. The exact cause is unknown but may involve damage to hair cells or abnormal neural activity in the auditory system. Around 40-50 million Americans experience chronic tinnitus, with around 2.5 million finding it debilitating. While the source is debated, it is thought to originate from changes in the brain rather than inner ear itself.

1. Tinnitus--Introduction AUD 733 Week 1