Vibration Modeling and Optimal Design of Differential Electromagnetic Transducer for Implantable Middle Ear Hearing Devices using the FEA

Among various kinds of hearing aids which have been developed so far, the conventional air conduction hearing aids have some problems such as the acoustic distortion, an howling effect due to acoustic feedback. Another type of hearing aid, the cochlear implant system can be applied to the profound imparied person. However, it shows the disadvantage that there is no possibility of recovery of the acoustic organ such as ossicle. On the other hand, the implantable middle ear hearing device directly vibrates the ossicular chain and has better sound quality, good cosmetics for appearance, and wide frequency responses so that it can overcome the defects of the conventional hearing aids. In this paper, a mathematical modeling and a momentum equation derivation of the DET has been performed. For the optimization of the structure dimension generating maximal vibrating force of the DET, the computer simulation using a finite element analysis (FEA) software has been performed. Also, the vibrating transducer has been designed to make the frequency characteristics of the transducer be similar to those of the normal middle ear. Through the experimental results, the measured vibration characteristics of the DET has been evaluated to verify the performance for the application to implantable middle ear hearing devices.