| Project Detail |
A wide range of hearing aid techniques can help people with hearing loss to communicate, but also insures their safety thanks to regained auditory warnings. Conventional hearing aids, worn in the external ear canal or behind the ear, re-quire no surgical interventions and are suited for patients with mild to severe hearing loss. Some patients cannot wear conventional hearing aids for anatomical reasons such as the absence of an external ear and ear canal. Others suffer from recurrent infections or allergic reaction when wearing conventional hearing aids. Another group are patients with one deaf ear [1]. In these situations, bone conduction hearing aids (BCHA) can be used if the inner ear loss does not exceed a certain threshold. BCHA can be coupled to the head in different ways, but they all convert an acoustic signal into a dynamic stimulation of the skull. A point force excites the bone and the surrounding soft tissue (skin and intra-cranial content), leading to the propagation of mechanical waves that create a pressure difference in the cochlea which in turn activates the hearing nerve. The transfer path of the stimulus to the cochlea is very complex, due to the material properties of bone, the fluid-structure interaction, and the dispersive elastic wave propagation that depends on the skulls geometry. In-vivo measurements of the cochlear response are scarce and unpractical. Efficient and accurate nu-merical models, an actual in-silico twin of the hearing aid, would mean a leap forward into understanding and develop-ing BCHA, e.g. for better directional hearing or to make optimal use of residual hearing. The aim of this project is to create a realistically fast, practical, and validated model of the acoustic response in the cochlea resulting from BCHA stimulation. Cutting-edge engineering methods, both experimental and numerical, will be combined with high-level clinical validation experiments. Two PhD students and a postdoc will collaborate to 1) deter-mine the dynamic properties of bone for audible frequencies, 2) deliver (micro-)CT scan data of and dynamic test re-sults on cadaver heads and 3) create a validated finite element model predicting the cochlear pressure resulting from BCHA. The project is jointly managed by University Hospital Zürich and the Empa lab for Acoustics/Noise Control. The collaboration between (micro-)mechanics specialists and clinical labs ensures the success of this project within a man-ageable consortium. Apart from the direct application to create better and more reliable hearing aids, and to understand the influence of individual skull geometries, the CHEWBACHA project will lead to several fundamental results. Firstly, very few studies have investigated the viscoeleastic properties of bone in the audible range. Second, the application of advanced finite element techniques (material homogenization, fluid-structure interaction, component mode synthesis) for hearing can be transferred to other biomechanical problems, or more general engineering applications. The input data and valida-tion measurements provided by the clinical partner are a unique crosslink ensuring the future use of the projects out-come. |
