Research Article A Three-Dimensional Finite-Element Model of a Human Dry Skull for Bone-Conduction Hearing Namkeun Kim, You Chang, and Stefan Stenfelt Department of Clinical and Experimental Medicine, Link¨ oping University, 58185 Link¨ oping, Sweden Correspondence should be addressed to Stefan Stenfelt; stefan.stenfelt@liu.se Received 11 April 2014; Revised 16 June 2014; Accepted 17 June 2014; Published 27 August 2014 Academic Editor: Nenad Filipovic Copyright © 2014 Namkeun Kim et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A three-dimensional inite-element (FE) model of a human dry skull was devised for simulation of human bone-conduction (BC) hearing. Although a dry skull is a simpliication of the real complex human skull, such model is valuable for understanding basic BC hearing processes. For validation of the model, the mechanical point impedance of the skull as well as the acceleration of the ipsilateral and contralateral cochlear bone was computed and compared to experimental results. Simulation results showed reasonable consistency between the mechanical point impedance and the experimental measurements when Young’s modulus for skull and polyurethane was set to be 7.3 GPa and 1 MPa with 0.01 and 0.1 loss factors at 1 kHz, respectively. Moreover, the acceleration in the medial-lateral direction showed the best correspondence with the published experimental data, whereas the acceleration in the inferior-superior direction showed the largest discrepancy. However, the results were reasonable considering that diferent geometries were used for the 3D FE skull and the skull used in the published experimental study. he dry skull model is a irst step for understanding BC hearing mechanism in a human head and simulation results can be used to predict vibration pattern of the bone surrounding the middle and inner ear during BC stimulation. 1. Introduction he human auditory nerve is connected to the microstructure called “organ of Corti (OC)” in the cochlea. he OC is located on the basilar membrane (BM). herefore, the motion of the BM is directly related to the ability to hear a sound. When the BM is stimulated by the luid pressure diference induced by the movement of the middle-ear (ME) structures (i.e., tympanic membrane, malleus, incus, and stapes), the hearing pathway is called air conduction (AC) [1]. On the other hand, when the BM is stimulated by vibration of the skull (or head), the hearing pathway is called bone conduction (BC). he mechanism of sound-energy transmission from the skull vibration to the BM motion is oten explained by ive contributors which are (1) inertia of the ME ossicles, (2) compression and expansion of the bony shell of the cochlea, (3) inertia of the cochlear luid, (4) deformation of the ear canal, and (5) sound pressure transmission from the cerebrospinal luid [2, 3]. However, the most important contributor for the BC driven BM vibration at diferent frequencies is still unclear. To reveal the dominant contributor for the BC driven BM motion, the cochlea and the skull/head vibrations have been investigated through experiments as well as simulations. For example, in order to study the cochlea in BC hearing, the BM velocities in human temporal bone specimens were investi- gated when the stimulation was by BC [4]. Recently, Chhan et al. [5] measured luid pressure of the chinchilla cochlea while manipulating the ME condition when stimulation was by BC. hrough the measurement of the luid pressure, they showed the signiicance of the cochlear luid inertia or compression in BC hearing. In addition, there are also numerous experiments for investigating the skull/head vibrations in BC hearing. Stenfelt et al. [6], using a dry human skull, investigated the mechanical point impedance (Z  ) and the acceleration response of the bone encapsulating the cochlea during BC stimulation at various positions on the skull. Furthermore, their study was extended to human cadaver heads [7], as well as live human skulls [8]. In this line of studies, the authors showed that there were diferences in the resonance frequency of Z  between the dry skull and cadaver and live human heads, and there were also diferences between Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 519429, 9 pages http://dx.doi.org/10.1155/2014/519429