Short Term Hearing Loss May Actually Be a Sign of Protection, Not Damage

A new study shows that the opposite is true when it comes to short-term hearing loss. As it was previously thought that this kind of noise could create long-term damage to our hearing, a new study shows that, in fact, this isn't the case.

University of South Wales Professor Gary Housley found that "reversible hearing loss" is a physiological adaptation mechanism, allowing the cochlea (the auditory portion of the inner ear) to perform normally when exposed to noise stress.

"This explains why we lose our hearing for hours or days after we have been exposed to a rock concert, for example. The adaptation mechanism has been switched on," he said.

The information from the study found that as sound levels rise, the cells in the cochlea release the hormone ATP, which in turn, binds to a receptor, causing the temporary reduction in hearing sensitivity.

Researchers found that mice without the receptor showed no loss of hearing sensitivity when exposed to sustained loud noise. However, the same mice were very vulnerable to permanent noise-induced hearing loss at very high noise levels.

Now that the team has shown the receptor is protective, the researchers are hoping to target this pathway to better protect the ear against noise in loud environments.

However, researchers note that while the cochlea can deal with loud sound on occasion, constant loud noise can lead to irreversible damage through the loss of high frequency hearing.

"It's like sun exposure," Housley said. "It's not the acute exposure, but the chronic exposure, that can cause problems years later."

Researchers caution that even those without a history of hearing loss could have cause for concern.

"Because our hearing sensitivity adapts, we can withstand loud noise, but we can't sense the absolute intensity of the sound and if we exceed the safe sound upper limit, we will damage our hearing -- despite this protective adaptation mechanism we have discovered," Housley said. "This is clearly the case for personal music devices, these deliver much higher sound levels into our ears than naturally occurred as our hearing sense evolved."

The research from this article is published in the journal Proceedings of the National Academy of Sciences (PNAS).