Finite Element Modeling of Viscoelastic Cochlear Components Under Acoustic and Blast Wave Transmission

Area of Science:

• Biomechanics
• Computational Auditory Neuroscience
• Finite Element Analysis

Background:

• Hearing loss and tinnitus are prevalent in veterans due to acoustic and blast overpressure.
• Previous finite element (FE) models of the organ of Corti (OC) lacked accurate viscoelastic properties.
• Understanding mechanical responses of cochlear structures to sound and blast is crucial for injury prevention.

Purpose of the Study:

• To develop and validate a microscale FE model of the organ of Corti (OC) incorporating viscoelastic material properties.
• To investigate the mechanical stress and strain on outer hair cells (OHCs) under acoustic and blast loading.
• To compare the predictive accuracy of viscoelastic versus linear elastic OC models.

Main Methods:

• A microscale FE model of the OC was created, representing a cochlear slice with sensory hair cells, membranes, and structural cells.
• Viscoelastic material properties were derived from experimental data for outer hair cells (OHCs) and the tectorial membrane.
• The model was subjected to simulated acoustic waves (90 dB at 800 Hz) and blast overpressure (30 kPa).

Main Results:

• The viscoelastic OC model predicted a phase lag and reduced peak stresses/strains for acoustic wave transmission.
• Blast simulations showed time-shifted peak stresses/strains and stress relaxation in the viscoelastic model.
• Significant differences in stress and strain were observed compared to a linear elastic OC model.

Conclusions:

• The viscoelastic FE model enhances the accuracy of predicting wave transmission and mechanical responses in cochlear hair cells.
• Viscoelasticity-induced phase/time lags and altered strain may influence the risk of inner ear biomechanical injury.
• This model advances the development of comprehensive, anatomically accurate multiscale models of the human ear.