Design Parameter Analysis of Round-Window Stimulating Electromagnetic Transducer: A Nonlinear Electromechanical Model

Abstract

Round-window stimulation is a new application of active middle-ear implants, extending their indications to mixed hearing loss. However, its clinical outcomes show large variations among patients. To investigate the factors influencing the performance of round-window stimulation, it is essential to construct a coupled model simulating the interaction between the electromagnetic transducer and the human ear. First, we developed a lumped-parameter model of the human ear incorporating the third window and a finite element model of an electromagnetic transducer that accounts for nonlinear electromechanical coupling. Then, the two models were integrated to establish a human ear–electromagnetic transducer coupling model. This model was validated by comparing its predictions of stapes response with experimental data. Based on this model, the effects of seven main transducer design parameters were analyzed. The results show that increasing the internal magnet mass enhances low-frequency output and lowers the resonant frequency, whereas increasing the external housing mass attenuates high-frequency output. A greater length of the permanent magnet slightly improves low-frequency hearing compensation. An increase in electrical conductivity result in a linear increase in transducer output, while a larger non-magnetic gap significantly diminishes hearing compensation. Additionally, larger rear support stiffness deteriorates low-frequency hearing compensation, whereas greater coupling layer stiffness enhances high-frequency compensation. The findings of this study provide valuable insights into the optimization of electromagnetic transducer for round-window stimulating active middle ear implants.

Keywords: Keywords: Electromagnetic transducer, Round-window stimulation, Active middle ear implants, Middle ear dynamics, Finite element analysis