Navigation Links
Hearing impaired ears hear differently in noisy environments
Date:9/11/2012

WEST LAFAYETTE, Ind. - The world continues to be a noisy place, and Purdue University researchers have found that all that background chatter causes the ears of those with hearing impairments to work differently.

"When immersed in the noise, the neurons of the inner ear must work harder because they are spread too thin," said Kenneth S. Henry, a postdoctoral researcher in Purdue's Department of Speech, Language and Hearing Sciences. "It's comparable to turning on a dozen television screens and asking someone to focus on one program. The result can be fuzzy because these neurons get distracted by other information."

The findings, by Henry and Michael G. Heinz, an associate professor of speech, language and hearing sciences, are published as a Brief Communication in Nature Neuroscience. The work was funded by the National Institutes of Health and the National Institute on Deafness and Other Communication Disorders.

"Previous studies on how the inner ear processes sound have failed to find connections between hearing impairment and degraded temporal coding in auditory nerve fibers, which transmit messages from the inner ear to the brain," said Heinz, who studies auditory neuroscience. "The difference is that such earlier studies were done in quiet environments, but when the same tests are conducted in a noisy environment, there is a physical difference in how auditory nerve fibers respond to sound."

Hearing loss, suffered in varying degrees by 36 million American adults, means there is damage to sensory cells in the cochlea and to cochlear neurons as well. The cochlea is the part of the inner ear that transforms sound into electrical messages to the brain.

In this study, the researchers measured a variety of physiological markers in chinchillas, some with normal hearing and others with a cochlear hearing loss, as they listened to tones in quiet and noisy environments. Chinchillas are used because they have a similar hearing range to humans, and background noise is used in the study to simulate what people would hear in a crowded room.

"The study confirmed that there is essentially no change, even for those with hearing loss, in terms of how the cochlear neurons are processing the tones in quiet, but once noise was added, we did observe a diminished coding of the temporal structure," Henry said.

The researchers focused on coding of the temporal fine structure of sound, which involves synchrony of neural discharges to relatively fast fluctuations in sound pressure. Both coding of fast fine structure information and coding of slower envelope fluctuations are critical to perception of speech in everyday listening environments.

"When noise was part of the study, there was a reduction in how synchronized the neurons were with the temporal fine structure," Henry said.

The auditory system filters sound into a number of channels that are tuned to different frequencies, and those channels vary based on their frequency tuning. In a normal system, the channels are sharp and focused, but they get broader and more scattered with hearing impairment.

"Now that we know a major physiological effect from hearing loss is that the auditory nerve fibers are particularly distracted by background noise, this has implications for research and clinical settings," said Heinz, who also has a joint appointment in biomedical engineering. "For example, most audiology testing, whether it is lab research or hearing-loss screenings, takes place in a quiet environment, but testing noisy, more realistic backgrounds is necessary to truly understand how the ear is processing sound. This also could influence the design of hearing aids and assistive technologies.

"Designers are often working on improving the temporal coding of the signal, but this research suggests that a primary focus should be on improving noise-reduction algorithms so the hearing aid provides a clean signal to the auditory nerve. Other ways people can reduce background noise include induction-loop hearing systems, which are used in churches and other public settings to provide a cleaner signal by avoiding room noise."

Next, the researchers plan to expand the study to focus on more real-world noises and coding of slower envelope information in sound.

"Additional study is certainly needed, and there are others who are also looking at the role the central nervous system plays, too," Henry said. "But ultimately, we found that hearing loss degrades temporal coding of sounds in background noise in the cochlea, the most peripheral level of auditory processing."


'/>"/>

Contact: Amy Patterson Neubert
apatterson@purdue.edu
765-494-9723
Purdue University
Source:Eurekalert  

Related medicine news :

1. Report: Strategies to prevent noise-induced hearing loss, tinnitus in soldiers
2. Rewired visual input to sound-processing part of the brain leads to compromised hearing
3. Not Enough Data to Advise Routine Hearing Screens for Older People: Experts
4. Suffering of Thousands Prompts FDA Hearing about Hip Implants
5. New screening test to help people with hearing loss in China
6. HIV Exposure Before Birth May Raise Kids Risk of Hearing Loss
7. Children exposed to HIV in the womb at increased risk for hearing loss
8. C-Section Babies May Be More Likely to Fail First Hearing Test
9. ASTRO chairman to testify at CARE Act hearing
10. Cone beam CT proves better for visualizing some causes of hearing loss at half the radiation dose
11. Grant awarded to help improve problem-solving skills for deaf and hard-of-hearing students
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Hearing impaired ears hear differently in noisy environments
(Date:6/27/2016)... ... June 27, 2016 , ... ... strategic partnership with Connance, a healthcare industry leader providing predictive analytics to ... technology combine to provide health systems, hospitals and ambulatory surgical centers with ...
(Date:6/27/2016)... KS (PRWEB) , ... June 27, 2016 , ... TopConsumerReviews.com ... retailers of Eyeglasses . , Millions of individuals in the United States and ... have become a way to both correct vision and make a fashion statement. Even ...
(Date:6/26/2016)... ... 2016 , ... On June 10-11, 2016, A Forever Recovery, a holistic treatment ... Longest Breakfast Table in Battle Creek, MI, where the rehabilitation facility is located. This ... of the world’s leading providers of cereal and other breakfast foods. Its residents often ...
(Date:6/26/2016)... ... ... PawPaws brand pet supplements owned by Whole Health Supply is ... of felines. The formula is all-natural and is made from Chinese herbs that have ... Kidney Support Supplement Soft Chews are Astragalus Root Extract and Rehmannia Root Extract ...
(Date:6/26/2016)... , ... June 26, 2016 , ... ... once they have been diagnosed with endometriosis. These women need a treatment plan ... require a comprehensive approach that can help for preservation of fertility and ultimately ...
Breaking Medicine News(10 mins):
(Date:6/23/2016)... BEVERLY HILLS, Calif. , June 23, 2016 ... faced the many challenges of the current process. Many of ... option because of the technical difficulties and high laboratory costs ... would have to offer it at such a high cost ... to afford it. Dr. Parsa Zadeh , ...
(Date:6/23/2016)... , June 23, 2016  In a startling report released today, ... their residents by lacking a comprehensive, proven plan to eliminate prescription ... definitive ranking of how states are tackling the worst drug crisis ... four states – Kentucky , New ... Vermont . Of the 28 failing states, three – ...
(Date:6/23/2016)... Research and Markets has announced the addition of the ... to 2022" report to their offering. ... financial data derived from varied research sources to present unique ... on the market during the next five years, including a ... markets, regional and country level analysis. The report provides a ...
Breaking Medicine Technology: