ANU Revisits Old Theories To Deal With Sound Damage From Loud MP3 Players
Nick Gilbert
at 15:03 PM Dec 1 2011
ANU Revisits Old Theories To Deal With Sound Damage From Loud MP3 Players
karmadude, flickr.com/photos/karmadude, Creative Commons
Science // 

A researcher at the Australian National University has proposed resurrecting a 150 year old theory of how sound is heard, so as to deal with noise damage caused by modern comforts like MP3 players and live music. If his findings are right, you could help prevent at least some damage to your ear as easily as by chewing a piece of gum.

Dr Andrew Bell, a part of the Research School of Biological Science at ANU, believes that the current emphasis on the cochlea in terms of auditory science is excessive, and that muscles in the middle ear play a much larger role in the transmission and limitation of sound than previously thought.

"The middle ear muscles have been ignored for 100 odd years, and I think it's time to revisit their role [in how sound is transmitted through the ear]," says Dr Bell to PopSci.com.au

The original pressure theory, also known as associated with the the resonance theory of hearing, was first formulated in the late 19th century, but was superseded by the travelling wave theory in 1960, on the back of significant of experimental data.

In a peer-reviewed paper recently published with the Journal of Hearing Science, Dr Bell sought to demonstrate why the travelling wave theory cannot adequately account for current empirical data, and why the out-of-fashion pressure theory offers a much simpler way to explain the way your ears deal with sound.

"If you close your eyes - some people can do this - and try to pull together the muscles around your ears, you can hear a fluttering. This is the sound of your middle ear muscles contracting," he says

He also says that doing this can create an apparent noise reduction of about 30dB, or about 1000 times fainter.

The travelling wave theory, which holds that noise is largely conducted along bones and cells connected to the cochlea (as opposed to resonating through changing air pressure conditions) can only account for at most a 100-fold reduction, according to Dr Bell.

If his findings are shown to be correct, Dr Bell believes instructing people to simply chew gum, talk or sing loudly at a concert could provide real benefits, compared to doing nothing at all.

While Dr Bell says people should be wearing ear plus at live music venues anyway, the fact that many simply don't means his findings could provide other ways for them to protect their hearing from irrevocable ear damage.

The pressure theory also makes the cochlea, located in your inner ear, into something more like "a box of electronics" that emits its own sounds, instead of simply being a passive instrument. Pressure changes in your ear such as those caused by your middle ear contracting act in a similar way to the gain control on an amplifier.

The paper represents around 20 years of study into the topic by Dr Bell.

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