An auditory perception due to aberrant spontaneous activity, arising from an altered state of excitation or inhibition within the auditory system. Large variability in prevalence stats: 10-15% of adults PST, 5% interferes with sleep or causes moderate-severe annoyance, and 0.5-1 % severe affect. 7% of UK population has consulted their GP specifically about tinnitus.
Prevalence increases with age, hearing loss & noise exposure. Defects at any point in the auditory system can induce tinnitus.