Case Studies

Hearing Aid Design is a Resounding Success
with Finite Element Analysis
GN ReSound uses realistic simulation from SIMULIA
to optimize product performance

The prevalence of hearing loss in the global population is estimated between 1.5 and 5 percent, depending on the definition of “deafness.” Deafness can be unilateral, bilateral, slight, moderate or severe. Hearing impairment can be conductive (caused by defects in the parts of the ear that conduct sound) or sensorineural (due to damage in either the inner ear or the auditory nerve). It can be congenital, or the result of accident, disease (viral or progressive), or drug toxicity. Total lack of hearing is actually rare, but when hearing loss occurs within the normal frequencies of human speech, it can create significant challenges at any age. The majority of people with less-than-average hearing are elderly, although environmentally-caused deafness (think machine shop noise, or loud music) can arise in younger adults. While implantable devices for the middle ear and cochlea have been developed for moderate-to-severe deafness, most cases of hearing loss can be ameliorated with externally-worn, behind the ear (BTE) hearing aids.

The hearing aid has come a long way from bulky mechanical devices like 18th-century ear trumpets and speaking tubes. Early electrical hearing aids were based on telephone technology invented by Alexander Graham Bell in the late 19th century, but they used heavy batteries and provided limited sound amplification with poor-to-moderate fidelity. Technology advances led to progressive miniaturization of devices during the 20th century so that today’s hearing aids are extremely light and comfortable to wear—and even come in “cool” colors and styles. But designing such hi-tech hearing aids can be a challenge.

Figure 1 A hearing instrument consists of a microphone, amplifier/computer, and receiver (or loudspeaker), all of which sit behind the external ear.  The microphone picks up sound from the outside world and transmits it to the amplifier/computer, which works like a normal PC with an operating system that simultaneously manages feedback suppression, speech enhancement, directionality improvement, and noise suppression.  The attenuated sound goes through the receiver into a sound tube and comes out through an internal earpiece (green).

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