A numerical study of the human ear

Hearing is one of the five senses in humans and one of the most important for their social life. The human ear is a complex organ which allows to understand and interpret sound waves for a band of frequencies between 16 Hz and 20 kHz and intensities ranging from 0 to 130 dB. The numerical model used in this work was built based on the geometrical information obtained from The visible ear project. A cryosectioning procedure was applied to the temporal bone of an 85 years old woman, without hearing pathologies, to obtain the anatomical data. Afterwards, the different tissues were hand-segmented and a 3D model was constructed. The finite element method was employed to obtain the umbo and stapes footplate displacements. A study of the external auditory meatus was carried out in order to study its influence on the human hearing. The model without the external auditory meatus was validated by comparing the displacements obtained for the umbo and stapes footplate, with other data in the literature. Subsequently, the external auditory meatus was introduced in the numerical model. The air was modelled with acoustic elements available in the Abaqus Standard software. In total, the model was discretized with 255 343 nodes and 1 345 379 elements. The results obtained showed the important role that the external auditory meatus has in amplifying the sound at higher frequencies. In the frequency band between 100 Hz and 10 kHz, two resonant frequencies were found. There was a significant gain in sound pressure near the tympanic membrane for the frequencies of 3 and 8 kHz. A phase shift of 180° near these frequencies, accompanied by a rapid increase in the displacement amplitude showed the presence of such resonances. The study can now proceed into the middle and inner ear in order to study the different types of pathologies and prostheses. The acoustic transmission in the cochlea remains understudied in this area.