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Science Capsule: Advances in Hearing Aid Research
Nearly 15 percent of American adults (37.5 million) aged 18 and over report some trouble hearing, making this one of the most prevalent disabling conditions in the U.S. Hearing loss can be hereditary, or it can result from disease, trauma, medications, or long-term exposure to damaging noise. The condition can vary from a mild but important loss of sensitivity to a total loss of hearing.
Sensorineural hearing loss is caused by a problem in the cochlea or the auditory nerve, which are parts of the ear that help sound impulses reach the brain. Hearing loss affects people of all ages, in all segments of the population, and across all socioeconomic levels. It can interfere with an individual’s physical, cognitive, behavioral, and social functions, and hearing aids are the main form of treatment. However, of adults aged 70 and older with hearing loss who could benefit from wearing hearing aids, fewer than 30 percent have ever used them. Of adults aged 20 to 69 who could benefit from hearing aids, the proportion that has used them is even lower (only about 16 percent).
A hearing aid works by amplifying sound to allow people to hear sounds that would not be audible. In specially equipped movie theaters, auditoriums, lecture halls, places of worship, and other areas, people can use a hearing aid to access “hearing loop” wireless signals that are beamed directly to the aid to bypass background noises. A vast array of hearing aid technology is available to provide additional features, such as the telecoil needed to pick up the hearing loop wireless signal.
Although the development of microelectronic components has enabled new digital hearing aid technology to replace earlier devices based on analog circuits, the underlying damage to the inner ear remains a limitation when the user is confronted by multiple speakers or background noise. Hearing aid users often complain of straining to focus on a single speech sound among competing sources at meetings, banquets, and sporting events. One solution to this problem is to move the hearing aid user closer to the person speaking and farther from the noise sources. Directional microphones offer another approach to do the same thing simply by pointing a device.
NIDCD-supported scientists have studied the remarkable directional hearing of the tiny fly Ormia ochracea, which inspired development of a novel directional microphone to improve hearing aids. Scientists reverse-engineered the physics and biology behind the fly’s abilities to localize sound and provided engineers with strategies to improve directional microphones that are small enough to use in hearing aids and help focus the aid on one sound source at a time.
Capitalizing on the knowledge learned from studying Ormia, another group of NIDCD-supported scientists successfully completed design and testing of a novel microphone based on these design elements. The scientists used silicon microfabrication technology to build the critical sensing elements needed for a functional microphone, characterize its function, and prove it had the capability to provide performance gains over existing designs.
Other NIDCD-supported scientists have continued research and development efforts based on this proof of concept prototype by adapting the microphone design into a form that could be more readily incorporated in a hearing aid. The scientists are the first to use piezoelectric materials, which turn mechanical pressure into electrical signals (voltage) and allow the microphone to operate with very little power. Because hearing aids rely on batteries, minimizing power consumption is a crucial design requirement.
The NIDCD recognizes that the needs of the majority of adults with hearing loss are not being met, and the cost and accessibility of hearing aids are considered part of the barriers to care. In response, the NIDCD is working to fill this need by supporting research or infrastructure that will lead to more accessible and affordable hearing health care for adults. The NIDCD cosponsored a consensus development study with the National Academies of Sciences, Engineering, and Medicine to consider hearing health care from the health care and population health perspectives, including the regulatory environment, access, and affordability. By identifying the research gaps related to effective and affordable hearing health care, devices, and compliance, and by developing novel strategies to overcome these gaps, NIDCD clinical and translational research will endeavor to improve the quality of life for millions of Americans with hearing loss.
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