Improving hearing aid technology by studying the inner ear

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Close up of a 3D printed scale model of a gerbil cochlea. The cochlea in the inner ear is where incoming sound waves trigger tiny hair cell vibrations. These vibrations are then converted into neurosignals which are transmitted to the brain. (Photo University of Rochester/J. Adam Fenster)

By Bob Marcotte, Senior Communications Officer for Science, Engineering and Research, University of Rochester

Will it ever be possible for hearing aids to compensate for hearing loss to the same degree that glasses and contact lenses correct our vision? Will hearing-impaired people possibly be able to separate a single conversation at a crowded party, hearing voices as clearly as corrective glasses and contact lenses can help us see a single tree in a forest?

Despite recent advances in hearing aids, a common complaint among users is that the devices tend to amplify all sounds around them, making it difficult to distinguish what they want to hear from background noise, Jong- said. Hoon Nam, researcher at the University. of Rochester.

Nam, a professor of mechanical and biomedical engineering, believes a key part of the answer to the problem lies inside the cochlea of ​​the inner ear. This is where incoming sound waves trigger tiny vibrations of hair cells, the sensory-receptive cells of the inner ear. These mechanical vibrations are then converted into neurosignals which are transmitted to the brain. An article detailing the research appears on the University’s website.

“Our lab’s mission is to explain the precise moment when this conversion occurs,” Nam said. This determination could provide the basic science needed for hearing aids to become fully capable of compensating for the unique degrees of hearing loss that occur from individual to individual, and from left ear to right ear, in each individual.

“No hearing aid should be the same,” Nam said.Three masked researchers pose for a portrait in Jong-Hoon Nam's lab.

“No hearing aid should be the same,” said Jong-Hoon Nam (center), pictured in his lab with research engineer Jonathan Becker ’15, ’17 (MS) (right) and PhD student Wei -Ching Lin. (Photo University of Rochester/J. Adam Fenster)

Nam’s research was funded by a recently renewed grant from the National Institutes of Health (NIH), which will total $4 million through 2025, plus nearly $800,000 in funding from the National Science Foundation (NSF). The two grants have helped Nam support seven doctoral students in mechanical engineering and biomedical engineering and enabled him to hire three to four undergraduate research assistants each summer.

His collaborations with colleagues from the departments of Mechanical Engineering and Biomedical Engineering, the University of Rochester Medical Center, and the University of Wisconsin Medical School have resulted in numerous articles. Recent highlights include:

microfluidic chamber used to study cochlear tissue.

Nam’s research group uses a specially designed microfluidic chamber to image cochlear tissue and see what’s going on at the cellular level. (Photo University of Rochester/J. Adam Fenster)

Optical Coherence Tomography Boosts Quantum Leap in Hearing Research

Nam uses the same tool that has helped ophthalmologists achieve breakthroughs in vision correction. Optical coherence tomography is an imaging technique that allows researchers to capture two-dimensional and three-dimensional images at micrometer resolution from biological tissues.

The technology has provided a leap forward in cochlear research, said Nam, whose lab occupies a unique niche in the field.

Other research groups are using imaging technology to study cochlear tissue vibration in living animals. However, the optical beam loses its power as it travels through skin and bone. Instead, Nam’s group images cochlear tissue in a specially designed microfluidic chamber, allowing his group to see what’s going on at the cellular level. “We can provide additional details that other researchers haven’t been able to see,” he said.

Other labs also tend to focus on animal models or computer simulations. As a result, they often encounter difficulties in interpreting the results of theoretical simulation groups, and vice versa. “This miscommunication is very costly and often adds confusion instead of advancing research,” Nam said.

Nam’s lab combines animal models and computer simulations. As a result, “we can be more confident in our conclusions; we can make new hypotheses that otherwise could not be tested,” Nam said.

Hearing aids have improved over the past decade. The latest digital hearing aids, for example, have automatic features that can adjust volume and programming for better hearing in different environments. Plus, Apple’s latest generation of attractive two-way earplugs have reduced the stigma of wearing hearing aids, even among young people.

“Now that looks cool,” Nam said. However, these hearing aids still fall short of the performance standards that have been achieved when it comes to vision correction.

According to Nam, there is still a long way to go. But new imaging and computer modeling technologies make this an exciting time for cochlear research, offering the promise of a comparable quantum leap in more effective aids and implants for the hearing impaired.

Source: University of Rochester

Pictures: University of Rochester / J. Adam Fenster

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