What causes tinnitus and why is it so persistent?

The answer

Tinnitus, the perception of sound without an external source (commonly ringing, buzzing, or hissing), affects roughly 10 to 15% of the global population. The most common cause is damage to the inner ear's hair cells from noise exposure, which reduces auditory input to the brain. In response, the auditory cortex increases its gain (sensitivity) to compensate for the missing signals, effectively 'turning up the volume' and generating phantom sound. This is analogous to phantom limb pain, where the brain fills in missing sensory information. Brain imaging shows that tinnitus involves not only the auditory cortex but also the limbic system (explaining the emotional distress it causes) and attentional networks. Because the sound is generated centrally in the brain rather than in the ear, it is extremely difficult to treat, though cognitive behavioral therapy, sound therapy, and neuromodulation approaches can significantly reduce its impact.