Japanese  
  Home  |  Top News  |  Most Popular  |  Video  |  Multimedia  |  News Feeds  |  Feedback
  Medicine  |  Nature & Earth  |  Biology  |  Technology & Engineering  |  Space & Planetary  |  Psychology  |  Physics & Chemistry  |  Economics  |  Archaeology
Top > Biology > Hearing Impaired Ears Hear Differently… >
Hearing Impaired Ears Hear Differently in Noisy Environments

Published: September 11, 2012.
By Purdue University
http://www.purdue.edu/

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."


Show Reference »


Translate this page: Chinese French German Italian Japanese Korean Portuguese Russian Spanish


 
This is form to send feedback to the editors. Tell us what you think about this article. All comments are not published. If you are looking for a response to a question please use our another feedback page.
Related »

Loss 
2/14/14 
Tinnitus Study Signals Advance in Understanding Link Between Loud Sounds Exposure And Hearing Loss
By University of Leicester
A research team investigating tinnitus, from the University of Leicester, has revealed new insights into the link between the exposure to loud sounds and hearing loss. Their study, …
Professor 
4/15/13 
Concert Cacophony: Short-term Hearing Loss Protective, Not Damaging
By University of New South Wales
Contrary to conventional wisdom, short-term hearing loss after sustained exposure to loud noise does not reflect damage to our hearing: instead, it is the body's way to cope. …
Cells 
8/29/12 
Earphones 'Potentially as Dangerous as Noise from Jet Engines,' According to New Study
By University of Leicester
Turning the volume up too high on your headphones can damage the coating of nerve cells, leading to temporary deafness; scientists from the University of Leicester have shown for …
Brain 
3/7/12 

Deafening Affects Vocal Nerve Cells Within Hours
By Duke University Medical Center
Brain 
2/5/14 
Simulated Blindness Can Help Revive Hearing, Researchers Find
By Johns Hopkins University
Minimizing a person's sight for as little as a week may help improve the brain's ability to process hearing, neuroscientists have found. Hey-Kyoung Lee, an associate professor of …
Loci 
4/27/12 
Novel Genetic Loci Identified for High-frequency Hearing Loss
By BioMed Central
The genetics responsible for frequency-specific hearing loss have remained elusive until recently, when genetic loci were found that affected high-frequency hearing. Now, a study published today in the open …
Kanold 
2/5/14 
A Short Stay in Darkness May Heal Hearing Woes
By University of Maryland
Call it the Ray Charles Effect: a young child who is blind develops a keen ability to hear things that others cannot. Researchers have long known that very young …
Hearing 
11/15/12 
South American Cricket Ears Shown to Rival Human Hearing
By University of Bristol
Scientists studying a species of South American bush cricket with some of the smallest ears known have discovered it has hearing so sophisticated that it rivals our own. …
Sounds 
6/25/14 

People with Tinnitus Process Emotions Differently from Their Peers, Researchers Report
By University of Illinois at Urbana-Champaign
Hearing 
5/10/11 
Sound Research at Acoustical Society Meeting
By American Institute of Physics
College Park, Md. (May 9, 2011) – The latest news and discoveries from the science of sound will be featured at the 161st meeting of the Acoustical Society of …
Cochlear 
4/23/14 

Hearing Quality Restored with Bionic Ear Technology Used for Gene Therapy
By University of New South Wales
Binaural 
9/20/12 
Two Bionic Ears Are Better Than the Sum of Their Parts
By American Friends of Tel Aviv University
Cochlear implants — electronic devices surgically implanted in the ear to help provide a sense of sound — have been successfully used since the late 1980's. But questions remain …
More » 
 
ScienceNewsline  |  About  |  Privacy Policy  |  Feedback  |  Mobile  |  Japanese Edition
The selection and placement of stories are determined automatically by a computer program. All contents are copyright of their owners except U.S. Government works. U.S. Government works are assumed to be in the public domain unless otherwise noted. Everything else copyright ScienceNewsline.