Computer assisted optimization of an electromagnetic transducer design for implantable hearing aids

Human temporal bones versus mechanical model to evaluate three middle ear transducers

“…Results of the mechanical middle ear model confirmed results of a computer model [22] regarding the dependence of the expected output on the width of the air gap. However, this computer model alone could not predict the order of magnitude of nonlinearity when the two components of the system touched.…”

“…The CLT (Figure 2(b)) was based on a minimally invasive implantable electromagnetic transducer design, described in detail by Stieger et al [22]. It consisted of a miniature disc-shaped coil (outer diameter 4.2 mm, length 0.3 mm) and a permanent magnet (samarium cobalt, diameter 3.2 mm, length 0.3 mm, axial magnetization).…”

31 Implantable Hearing Devices

“…The necessary electromechanical transducer may work on an electromagnetic or piezoelectric basis (Table 2) [26], [27]. In the context of electromagnetic transducers, the vibrations are generated between a current-supplied coil and a magnet [28], for piezoelectric transducers, they are gen- erated by the current-induced relative change in the length of a piezoelectric crystal [29]. For the use in active middle ear implants, both systems have specific advantages and disadvantages.…”

Finite element analysis of the coupling between ossicular chain and mass loading for evaluation of implantable hearing device

“…The magnet may be mounted outside the coil (extra-coil electromagnet (ECE)) or within the coils (intra-coil electromagnet (ICE)). Several authors have proposed simpler ECE device, such as contactless electromagnetic transducer (CLT) consisting of a coil and a permanent magnet (Goode et al, 1995;Hamanishi et al, 2004;Hough et al, 2000;Huber et al, 2006;Maniglia et al, 1996;Perkins et al, 2010;Stieger et al, 2004). The magnet was attached to the ossicular chain in various locations, or was placed on the tympanic membrane.…”

“…It is important to ensure optimal positioning of the transducer and firm attachment of the clip along ossicular chain so it can work most efficiently. Stieger et al (2004) used both computer simulations and experimental measurements to analyze the influence of changes in geometry and relative placement between the coil and magnet on the force generated by the CLT. However, crimping of the clip may not always produce fine attachment, as suggested by Snik and Cremers (2004), this might be one of the causes of the variation in hearing benefit between patients.…”