A totally implantable hearing system - Design and function characterization in 3D computational model and temporal bones

Implantable middle ear hearing devices are emerging as an effective technology for patients with mild to moderately severe sensorineural hearing loss. Several devices with electromagnetic or piezoelectric transducers have been investigated or developed in the US and Europe since 1990. This paper reports a totally implantable hearing system (TIHS) currently under investigation in Oklahoma. The TIHS consists of implant transducer (magnet), implantable coil and microphone, DSP-audio signal processor, rechargeable battery, and remote control unit. The design of TIHS is based on a 3D finite element model of the human ear and the analysis of electromagnetic coupling of the transducer. Function of the TIHS is characterized over the auditory frequency range in three aspects: (1) mass loading effect on residual hearing with a passive implant, (2) efficiency of electromagnetic coupling between the implanted coil and magnet, and (3) functional gain of whole unit in response to acoustic input across the human skin. This paper focuses on mass loading effect and the efficiency of electromagnetic coupling of TIHS determined from the FE model of the human ear and the cadaver ears or temporal bones. Some preliminary data of whole unit function are also presented in the paper.