Development of a non-implantable electromagnetic hearing aid

Research and development over the past two decades has shown that implantable hearing aids can circumvent some of the problems found in conventional hearing aids, such as feedback, cosmetic problems and so on. However, these hearing aids have not as yet been widely used, because invasive surgery has to be performed to implant them and applying them in children, who are still growing, is difficult. In this study, a prototype of the non-implantable electromagnetic hearing aid, which can generate a high-excitation force to vibrate the ossicles via the tympanic membrane, was constructed. The hearing aid consists of an electromagnetic transducer and an amplifier. To determine fundamental properties of the hearing aid, excitation force and acoustical gain were evaluated using an artificial middle ear and a human temporal bone, respectively. The experiments showed that the hearing aid was able to generate the maximum excitation force, which is equivalent to a sound pressure of 100 dB SPL at high frequencies.