Mechanics of the middle ear

Ondertitel:optical measurements and finite-element modeling

The middle ear plays a crucial role in our ability to hear and performs very well under various circumstances. However, some pathologies or situations prohibit the middle ear from functioning as intended. In this work, the mechanical functioning of the mammalian middle ear under different circumstances was investigated using optical measurement techniques and finite-element modelling. The nonlinear characteristics of the acoustic vibrations of the middle ear at high intensity sounds were evaluated using laser Doppler vibrometry. We further investigated the source of this nonlinear behavior by developing finite element models. Using similar models, we investigated the effect on sound transmission when the first hearing ossicle, the malleus, is fractured. We found that the limited transmission did not simply occur due to a lack of contact between the broken parts. The shape and functionality of the eardrum was affected by the malleus fracture as well, due to eardrum prestrain. However, the current models do not incorporate such prestrain of the eardrum and no experimental data was available. Therefore, we built a digital image correlation setup to investigate and measure eardrum (pre-)strain. The measured data allow for further model validation. To facilitate model validation, we also developed a data processing technique allowing for frequency response averaging without losing individual curve characteristics. This provides modelers more accurate data to compare their simulations with. In a last project, we developed a technique to diagnose several middle ear pathologies which immobilize the ossicles. The current methods to evaluate which ossicles are immobilized depend on the surgeon’s experience. Using laser Doppler vibrometry, we developed a technique which is minimally invasive for the patient and returns quantitative data about the mobility of the ossicles. This facilitates decision making and can prevent unnecessary surgeries. In summary, the insights in the mechanical principles of the mechanical ear obtained in this work are a step towards improved finite element models and clinical evaluation of ossicular fixations.

Jaar van publicatie:2019

Trefwoorden:Doctoral thesis

Toegankelijkheid:Open