h1

TY  - THES
AU  - Kersten, Simon
TI  - Modeling and analysis of vibroacoustic mechanisms in hearing
PB  - Rheinisch-Westfälische Technische Hochschule Aachen
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2025-07039
T2  - Aachener Beiträge zur Hörtechnik und Akustik
SP  - 1 Online-Ressource : Illustrationen
PY  - 2025
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1  - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2025
AB  - Despite significant technological advancements in recent decades, users of hearing aids and hearing protection often report dissatisfaction due to an ünnatural" auditory experience. These challenges highlight gaps in our understanding of the physical mechanisms underlying hearing – a complex vibroacoustic phenomenon involving interactions between the sound field in the outer ear, the mechanics of the middle ear, and the fluid dynamics of the inner ear. Hearing not only involves the air conduction (AC) pathway via the outer and middle ear, but also various bone conduction (BC) pathways via which sound is transmitted to the inner ear. BC hearing plays a crucial role in audiological applications such as BC audiometry and BC hearing aids, where vibrations are directly induced in the skull. Another phenomenon involving both AC and BC is the occlusion effect (OE): occluding the ear canal (EC) alters own-voice perception, which is a major cause of the dissatisfaction with hearing technologies. Experimentally assessing the physics underlying hearing poses significant ethical and technical difficulties. Therefore, modeling and numerical simulations are essential tools for advancing our understanding. These investigations also require examining the vibroacoustic behavior of the inner ear, because it serves as the sensor for all AC and BC pathways. Recent studies challenge the classical view on inner ear mechanics by highlighting the flexibility of the cochlear partition (CP), particularly the osseous spiral lamina (OSL) and cochlear partition bridge (CPB). The roles of these structures are poorly understood, because experimental data on CP motion remain sparse and spatially limited and most inner ear models consider the OSL and CPB rigid. This thesis advances our understanding of the vibroacoustic mechanisms in AC and BC hearing by systematically separating the auditory system into subsystems. First, the structural motion of the EC is analysed, with particular emphasis on how the motions of the EC entrance and tympanic membrane interact with the vibrations of the EC wall in generating the EC sound pressure underlying the OE. An impedance boundary condition is introduced to account for these contributions in OE models. Circuit calculations, based on an EC motion extracted from a finite element model of a human head, reveal that the motions of the EC entrance and tympanic membrane affect the EC sound pressure at low frequencies, especially under occluded conditions. This finding may help reconcile discrepancies between OE simulations and experimental data. Second, an anatomical finite element model of the human inner ear is introduced, allowing the OSL and CPB to be modeled as either rigid or flexible structures. When applying stimulation at the oval window – representing AC and BC transmission via this pathway – the simulations reveal that the OSL significantly influences cochlear impedances, CP stiffness, and overall CP motion. Furthermore, when incorporating the rigid body motion of the inner ear during BC, the simulations identify a compressional motion of the OSL that increases the differential volume velocity at the round window compared the oval window, offering an alternative explanation for experimental observations previously attributed to "third-window" effects in BC hearing. These findings highlight the importance of considering the flexibility of the OSL and CPB when interpreting experimental data, challenging classical concepts of inner ear function that assume a rigid OSL and neglect the CPB. Overall, the results suggest that the OSL plays a more important role in both AC and BC hearing than previously recognized. While this work advances our understanding of hearing by focusing separately on different auditory subsystems, future work should integrate these insights into comprehensive models, such as full-head finite element simulations, to further elucidate the interactions between the AC and BC pathways and their relative importance. Ultimately, these findings will contribute to improvements in hearing technologies, including hearing devices, hearing protection, and BC hearing aids.
LB  - PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
DO  - DOI:10.18154/RWTH-2025-07039
UR  - https://publications.rwth-aachen.de/record/1016952
ER  -