When loud noises damage the inner ear, many people experience hearing loss and some complain of tinnitus, a buzzing or ringing in their ears. Karl Kandler at the University of Pittsburgh in Pennsylvania and his colleagues exposed mice to 45 minutes of loud noise. A week later, the researchers found that all exposed mice had experienced hearing loss, and about half of them failed to detect silent gaps in background noise, a sign of tinnitus in animals. In all mice with hearing loss, neuronal circuits associated with hearing were reorganized; neurons in these circuits were more likely to fire in animals with symptoms of tinnitus.
Exposure to white noise of moderate intensity for seven days after the loud noise prevented these circuit changes and decreased the proportion of mice with tinnitus symptoms from 51% to 12%.