Development of a new electromagnetic hearing aid using lightweight coils to vibrate the ossicles via the tympanic membrane

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A newly developed electromagnetic hearing aid can generate high-excitation force to vibrate ossicles via the tympanic membrane by repulsive force, which acts between the magnet and the vibrator coil attached to the tympanic membrane. Therefore, to obtain the high-excitation force, it is important to evaluate a magnetic field generated by the vibrator coil.First, a driving coil, which applies an electrical current to the vibrator coil, was designed so as to generate the greatest excitation force. Optimally designed coil was then coupled to an amplifier and the excitation force generated by the hearing aid was measured using an artificial middle ear, which simulates middle ear of the human. The following conclusions can be drawn.1. When a sound pressure of 60 dB SPL (normal speech level) was applied to the newly developed hearing aid, it generated the excitation force of 100 dB SPL in terms of sound pressure above 3 kHz. This value is sufficient to treat patients with sensorineural hearing loss up to 80dB HL.2. The excitation force of this hearing aid was not sufficient at tow frequencies. This result indicates that improvement of the amplifier is necessary further.