| dc.description.abstract | Hearing loss caused by blast exposure is an inherent risk that active Service members face due to the operational activities they engage in. With auditory system dysfunction dominating service-connected disabilities among Veterans, there is an urgent need to better understand the effects of blast exposure on the auditory system, particularly the effects of repeated low-intensity blast exposure on progressive hearing loss. Furthermore, the analysis of blast wave transmission in the ear is needed.
This thesis focuses on an experimental study using chinchilla animal model. Chinchilla with and without earplugs were exposed to repeated low-intensity blasts. Hearing function tests reflecting the state of the auditory system were measured prior to blast, after blast, and were then monitored over 14 days.
This thesis also reports the creation of the first finite element model of the entire chinchilla ear, including spiral cochlea. A finite element (FE) model of the chinchilla cochlea was integrated with our lab’s previously published FE model of the chinchilla middle ear. The model was first evaluated for simulating acoustic sound transmission. A uniform acoustic pressure applied as an input and harmonic response analysis was conducted. The model was then validated by comparing model-predicted movements of ear structures with experimental measurements.
The FE model of the entire chinchilla ear was then adapted for blast wave analysis. Pressure waveforms measured during chinchilla blast exposure studies were applied to the model as input. The model-predicted waveforms at locations within the ear were then compared with experimental waveforms recorded in the same locations. Movement of structures within the ear were also predicted.
The work presented in this thesis improves our understanding of the effects of blast exposure on the auditory system. Experimental data collected from chinchilla animal model provides insight into the effect of low-intensity blasts on hearing damage, which is not well studied. Moreover, this study provides information on the central auditory system, which is lacking in the literature. Furthermore, this thesis reports the first FE model of the entire chinchilla ear. This model provides a computational tool to simulate the sound or blast wave transmission through the chinchilla ear, explain experimental observations in animal model of chinchilla, and help translate animal experimental data to human responses to blast exposure. Future work includes further investigation of different blast conditions (e.g. number of blasts, blast intensity, recovery time, etc.) on hearing loss and improvement of the FE model for blast wave analysis. | en_US |
