Tinnitus arises when this flexibility goes bad. Things may start to go awry when toxic drugs, loud noises, or even whiplash cause damage to the nerve hairs in the ears. The injured nerve hairs can no longer send signals from the ear to the tone map. Bereft of incoming signals, the neurons undergo a peculiar transformation: They start to eavesdrop on their neighbors, firing in response to other frequencies. They even start to fire sometimes without any incoming signals. As the brain's feedback controls get rewired, the neurons end up in a self-sustaining loop, producing a constant ringing. That is why tinnitus often doesn't go away when people get their auditory nerve surgically cut.