Sydney: A relook at a 150-year-old theory could open the way to better noise protection.

Andrew Bell from the Research School of Biology, Australian National University (ANU), says the long-discarded 'pressure theory' could be the answer to protecting people from damagingly loud sound levels.

"Hearing loss used to be called 'blacksmith's disease'. In the modern age, it might come to be called MP3 disease," said Bell, the Journal of Hearing Science reports.

The middle ear consists of three tiny bones and two miniature muscles which tense up to protect the ear from loud sounds, according to an ANU statement.

Bell said these bones and muscles work together as a tiny pump, raising the pressure of the fluid in the inner ear - like pushing a cork into a bottle of water.

It is the increased pressure that softens the impact of loud noises on the delicate cells that process sound.
"If we can find a way to make the middle ear muscles 'pump' more effectively, like they seem to do in tough ears, we could provide better protection against noise," Bell said.

The pressure theory was first put forward more than 150 years ago and has since been dismissed. But with the risk of hearing damage associated with the now ubiquitous MP3 player, Bell believes the theory is due for revival.

"Current theory contradicts data from hearing studies," Bell said. "Pressure theory can help explain these inconsistencies."