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Posted on Tuesday, January 27, 2015

The Effects of Loud Noise on the Ear

For a long time government and doctors have rightly warned about the dangers of noise induced hearing loss (NIHL). NIHL is caused when the delicate hairs within the inner ear are damaged by sound, so sound measurements called decibels are used to determine if certain sounds will damage hearing. As it turns out, there may be an even more delicate part of the ear that needs to be protected and the standards previously in effect to guard against NIHL may need to be reevaluated.

It turns out that noise damages more parts of hearing than previously thought. Researchers at the Acoustical Society of America have now shown that hair cells are only part of the equation when it comes to noise induced hearing loss. The other part are the nerve fibers that connect to these hair cells. The nerve fibers are responsible for helping to awaken the cochlear nerve which transmits sounds. Because these nerve fibers are hard to see and because the loss of hearing that occurs with damage to these fibers is not measured by current hearing tests, they have been largely ignored when determining hearing loss and when determining the standards used for protecting hearing.

According to an article in Science Daily, "First, the field of auditory neuroscience didn't appreciate until recently that you can lose up to 90 percent of your cochlear nerve fibers without a change in the ability to detect a tone in quiet," he said. "Tone detection in quiet is the basis of the threshold audiogram -- the gold standard test of hearing function. The fact that thresholds may transiently elevate and then recover within hours or days after an acoustic overexposure doesn't mean that the inner ear has recovered."

Developing tests to see and evaluate the damage to these very small areas of the ear was a complicated process and the major reason that this hearing damage has remained hidden for so long. Now that researchers and physicians are aware of this extremely delicate area within the ear, the standards that have been in use for evaluating hearing loss will need to be updated, along with the warnings given to people about what constitute "too loud." In order to play it safe, people should protect their ears when experiencing any amount of continuous noise--for example a stylist using a hair dryer-- and if possible should avoid any level of sound that is even mildly uncomfortable. Hopefully new standards for protecting ears from NIHL will be developed soon.

Want to learn more about hearing loss? Then please watch this quick and informative video!

References
Acoustical Society of America (ASA). "Noise-induced 'hidden hearing loss' mechanism discovered." ScienceDaily. ScienceDaily, 7 May 2014. .

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