An electromagnetic hearing aid using coils to vibrate the ossicles-evaluation of excitation force and distortion

In this study, as the first stage in the development of a non-implantable hearing aid, a new electromagnetic transducer composed of three coils and a magnet was made which generates high-excitation force to vibrate ossicles via the tympanic membrane. To evaluate the excitation force of the electromagnetic transducer, cochlear microphonic (CM) was measured in anesthetized guinea pigs. The non-implantable electromagnetic hearing aid consists of two parts, i.e., an electromagnetic transducer and an amplifier. Results show that over the entire frequency, CM amplitude caused by the electromagnetic transducer is larger than that caused by acoustical stimulus. Because of the linear relationship between the acoustical stimulus level and the CM amplitude, the value of the excitation force caused by the electromagnetic transducer can be converted to the equivalent value in dB SPL. The excitation force generated by the prototype of electromagnetic transducer is 93-106 dB SPL in the frequency range of 0.5 to 10 kHz. This study showed that the electromagnetic transducer is able to generate sufficient excitation force to treat patients with high-frequency hearing loss.