The development of a non-surgical direct drive hearing device with a wireless actuator coupled to the tympanic membrane

A non-surgical, direct driving hearing device with an actuator placed on the tympanic membrane was designed, fabricated and tested. The actuator consisted of two photodiodes, an aluminum ring, two neodymium iron permanent magnets, two opposing wound coils, a latex membrane and a Provil Novo™ membrane. The transducer coupled to the ear drum-utilizing photodiodes and permanent magnets on the motive components could eliminate the need for electrical connections to the moving components. An optic probe was designed to allow sound and light signals to enter the ear canal. By using opto-electromagnetic coupling, the developed hearing device could transmit information over a distance without using cables. The wireless actuator was achieved by two configurations: in one, two light emitting diodes were used for carrying the input signals, and in the other, the corresponding photodiodes were used for receiving the light signals and generating the currents in the actuator. The wireless actuator was designed to use light to carry energy and transmit the signals; thus, the occlusion effect created by traditional ear molds could be avoided. Finally, the wireless actuator was fabricated and tested with a laser Doppler vibrometer. The actuator showed displacements of vibration between 30–0.2 nm and from 400 Hz to 7 kHz with reduced vibration at higher frequencies. The gain of the actuator with 120 μA on the umbo displacement was approximately 3–13 dB from 400 to1500 Hz and decreased to 6 dB between 1500 Hz to 3 kHz and down to −1 to −6 dB above 3 kHz. Distortions of the umbo vibration amplitude were approximately −1 to −10 dB across frequencies. The results suggest that light can transmit the sound signal remotely and that adequate amplification can be achieved by this actuator. The reduced amplitude above 3 kHz was a consequence of the mass effect of the actuator, which should be miniaturized in the future.