There are about 85,000 severely hearing-impaired people in Japan who cannot hear, even with the use of a conventional hearing aid. Although cochlear implants can restore hearing ability, their performance is not very satisfactory. On the other hand, bone-conducted ultrasonic waves can be experienced as sound, not only by people with normal hearing ability but also by severely hearing-impaired people. AIST has objectively proven, for the first time in the world, that bone-conducted ultrasonic waves can be sensed as sound, and that speech can be detected by this means. AIST is now developing a bone-conducted ultrasonic hearing aid for practical application. Up to now, we have achieved revolutionary results using our prototype bone-conducted ultrasonic hearing aid: more than half of our severely hearing-impaired subjects were able to sense sound, and about 20% were able to understand speech (See Fig.).

Our bone-conducted ultrasonic hearing aid is far easier to attach than a cochlear implant, which requires surgery. It thus substantially removes the mental and physical burden experienced by cochlear implant users. Moreover, it also can be used to treat tinnitus in severely hearing-impaired people. Thus, substantial clinical effects are expected of the bone-conducted ultrasonic hearing aid.