Converging evidence suggests that tinnitus (ringing of the ears) is generated by synchronous neural activity that develops in regions of the primary auditory cortex which have lost their input from the ear.  Diminished intracortical inhibition consequent on hearing impairment is a likely triggering factor but may not be accurately indexed by the clinical audiogram.  We will present psychoacoustic and functional brain imaging data (MEG and EEG) which favor these hypotheses, and extend the analysis to residual suppression of tinnitus by masking sounds.  The results emphasize the importance of preventing hearing injuries and suggest approaches that may reduce tinnitus in existing cases.  As we learn more about tinnitus, we learn more about how the brain generates the sensation of sound.