Low-level noise exposure for prolonged periods may cause damage to the auditory areas of the brain and impair normal listening processes reports a paper in Nature Communications this week. These findings reveal that listening processes are perhaps more susceptible to damage then previously thought.
Listening processes involve processing sound waves into neuronal activity in the auditory cortex of the brain. Many prior studies have shown that persistent exposure to high-level noise, results in detrimental functional changes in listening processes. It had always been assumed, however, that noise levels deemed to be safe did not cause such problems.
Xiaoming Zhou and Michael Merzenich expose adult rats to structured low level noises that are generally accepted to be 'safe', over periods of 10 and 24 hours for 2 months. They find that chronic exposure to these low-level sounds results in damage to the auditory cortex and an impairment in sound discrimination. In addition, almost equally strong effects resulted from both the 10 hour and 24 hour daily exposure regimens.
Although the exposure times used in rats may not be representative of everyday life for humans, the authors suggest that it highlights a potential need to redefine noise safety levels.