Hearing loss, difficulty distinguishing speech can be caused by prolonged exposure to loud noises

By: Dr. Victor Marchione | Hearing Health | Sunday, April 24, 2016 - 08:30 AM

Hearing loss caused by prolonged exposure to loud noisesIt’s no surprise that loud noises can be bad for your ears and contribute to hearing loss. But you might not know exactly how severe the damage could be.

New research is now showing those loud noises could be having an impact on your brain cells, too.

Research from the University of Texas at Dallas showed that prolonged exposure to loud noises can change how speech is processed by the brain. These changes could increase difficulty in distinguishing speech.

The findings, which were published in journal Ear and Hearing, represent new knowledge about the way noise-induced hearing loss (NIHL) affects how the brain relates to speech.

How does hearing loss affect the brain?

For the study, scientists exposed rats to moderate or intense levels of noise, which were designed to stimulate the two types of noise trauma faced by clinical populations, for one hour. One group heard a high-frequency noise at 115 decibels, which induced moderate hearing loss. The other heard a low-frequency noise at 124 decibels, causing severe hearing loss.

One month after the noise exposure, results were analyzed to see how the groups responded to the noises. Neurons on one end of the auditory cortex respond to low-frequency sounds, while the other end responds to high-frequency sounds.

In the rats with severe hearing loss, less than one-third of the tested auditory cortex sites reacted to sound stimulation. Those areas that did react did so in unexpected ways like slower neuron reaction.

Rats that could successfully complete a behavioral task before the sound exposure were no longer able to distinguish between speech sounds. On the other hand, the rats with moderate hearing loss saw no changes. A large area of the auditory cortex responded to low-frequency sounds after the hearing loss, while the parts that responded to high-frequency sounds responded more slowly and needed more intense sound stimulation.

Regular exposure to sounds above 100 decibels can lead to permanent hearing loss

To give a comparison between the study noises and ones we might encounter in day-to-day life, the American Speech-Language-Hearing Association lists the sound of a chainsaw or the top output for an MP3 player at 110 decibels, while an emergency siren is 120 decibels. The National Institute of Deafness and Other Communication Disorders (NIDCD) warns that regular exposure to sounds above 100 decibels, for more than a minute at a time, can lead to permanent hearing loss.

Impact of noise on our hearing

Increased risk of hearing loss due to noise and loud sounds may be one price we are paying for our increasingly modernized society.

“As we have made machines and electronic devices more powerful, the potential to cause permanent damage has grown tremendously,” study coauthor Dr. Michael Kilgard says. “Even the smaller MP3 players can reach volume levels that are highly damaging to the ear in a matter of minutes.”

Excessively loud sounds can cause hearing loss because they permanently damage the hair cells that act as the ear’s sound receivers and those cells don’t regenerate. NIHL can affect people of all ages. An estimated 15 percent of Americans aged 20 to 69 experience noise-induced hearing loss.

Who wants that? Take note the next time you’re near a construction worksite (oh, those electric saws and jackhammers!) or listening to music, full-blast, in the privacy of your home.


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Sources:

http://www.utdallas.edu/news/2014/7/31-31061_Study-Noise-Induced-Hearing-Loss-Alters-Brain-Resp_story-wide.html?WT.mc_id=NewsHomePageCenterColumn

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