Optimization and Performance Evaluation of a Transducer for Bone Conduction Implants

Abstract

We designed and implemented an electromagnetic transducer for implantable bone conduction hearing aids. The proposed transducer is smaller than previous bone conduction transducers for easy implantation and was designed using high permeability metals to produce large electromagnetic forces. In addition, the number of cantilever beams was changed from two to three to minimize distortion of the transducer, potentially due to twisting of the cantilever beam. The proposed transducer consists of a titanium cover with three screw holes, a metal ring, a circular plate, a vibrational membrane with a three-cantilever structure, a metal plate and cylinder, a permanent magnet, top and bottom coils, and a cylindrical titanium case. The transducer was optimally designed based on analysis of electromagnetic and mechanical vibrations, and the target resonance frequency was derived by controlling the variable elements of the vibrational membrane. The transducer was manufactured based on the results of finite element analysis, and the validity of the design was verified by comparing the results of vibration measurement experiments and a simulation. Finally, to evaluate the performance of the proposed transducer, the transducer was attached to the mastoid of participants and functional near-infrared spectroscopy was used to measure brain activation changes of the auditory cortex due to vibration stimulation. INDEX TERMS Implantable bone conduction hearing aid, electromagnetic transducer, finite element analysis, functional near-infrared spectroscopy.

Design Study of a Round Window Piezoelectric Transducer for Active Middle Ear Implants

“…The output characteristics of the piezoelectric transducer were measured using a non-contact vibration measurements system consisting of a data acquisition unit (NI PXIe-8840 controller, NI PXIe-1071 chassis and NI PXI-4461 sound-vibration module; National Instruments Corp., Austin, TX, USA) and a single-point laser Doppler vibrometer (LDV; OFV-551 sensor head and OFV-5000 controller; Polytec GmbH, Waldbronn, Germany) [ 32 ]. The measurement system generated a sinusoidal signal to drive the piezoelectric transducer, and simultaneously collected the vibration signals of the piezoelectric transducer measured by the LDV ( Figure 8 a).…”

An Assembly Quality Inspection System for Bone Conduction Implant Transducers

“…Therefore, a system that can check for misalignment between transducer components before the transducer is fully assembled is needed. To manufacture a transducer for use in the experiment, the specifications of the transducer made by Lee et al [31] were used without modification. Here, unlike the previous transducers, the number of cantilevers was increased from three to four because when a vibrational membrane has the same resonance frequency, a vibrational membrane composed of three cantilevers is longer than when there are four cantilevers.…”

“…The mechanical resonance frequency of the transducer was adjusted using a vibrational membrane with a multiple-cantilever structure. Lee et al [31] improved the miniaturization and frequency characteristics so that the prototype transducer could be used as a BCI. The output characteristics of the improved transducer were evaluated by functional near-infrared spectroscopy (fNIRS).…”

“…The improved transducer reported by Lee et al [31] has a permanent magnet coupled to the center of a vibrational membrane composed of three cantilevers. When a current flows through the coil, the magnet vibrates due to the interaction between the coil and magnet.…”

“…The measurement system consists of an XY stage and two digital scale calipers capable of expressing a position coordinate system. To minimize the distortion of the cantilever, the number of cantilevers in the transducer structure of Lee et al [31] was changed from three to four, with the remaining components manufactured in the same way. In addition, the XY coordinate system of the cantilever shape was derived using finite element analysis (FEA) software.…”