Numerical simulation of wave propagation in a realistic model of the human external ear

Abstract

In this study, a numerical investigation is performed to evaluate the effects of high-pressure sinusoidal and blast wave's propagation around and inside of a human external ear. A series of computed tomography images are used to reconstruct a realistic three-dimensional (3D) model of a human ear canal and the auricle. The airflow field is then computed by solving the governing differential equations in the time domain using a computational fluid dynamics software. An unsteady algorithm is used to obtain the high-pressure wave propagation throughout the ear canal which is validated against the available analytical and numerical data in literature. The effects of frequency, wave shape, and the auricle on pressure distribution are then evaluated and discussed. The results clearly indicate that the frequency plays a key role on pressure distribution within the ear canal. At 4 kHz frequency, the pressure magnitude is much more amplified within the ear canal than the frequencies of 2 and 6 kHz, for the incident wave angle of 90° investigated in this study, attributable to the '4-kHz notch' in patients with noise-induced hearing loss. According to the results, the pressure distribution patterns at the ear canal are very similar for both sinusoidal pressure waveform with the frequency of 2 kHz and blast wave. The ratio of the peak pressure value at the eardrum to that at the canal entrance increases from about 8% to 30% as the peak pressure value of the blast wave increases from 5 to 100 kPa for the incident wave angle of 90° investigated in this study. Furthermore, incorporation of the auricle to the ear canal model is associated with centerline pressure magnitudes of about 50% and 7% more than those of the ear canal model without the auricle throughout the ear canal for sinusoidal and blast waves, respectively, without any significant effect on pressure distribution pattern along the ear canal for the incident wave angle of 90° investigated in this study.

Morphology of human ear canal and its effect on sound transmission

“…20 Fadaei et al applied this method to investigate the high-pressure sinusoidal and blast wave propagation in the EC. 7 The findings revealed that frequency plays a key role in the pressure distribution within the EC. At a frequency of 4 kHz, the pressure magnitude is increased significantly within the EC than adjacent frequencies.…”

“…At a frequency of 4 kHz, the pressure magnitude is increased significantly within the EC than adjacent frequencies. 7 Garcia-Gonzalez et al investigated the interactions between the tympanic cavity, EC, and TM and found that the presence of the tympanic cavity introduces a second resonance in middle ear transfer functions at >3 kHz. 21 Qi et al studied a 3D nonlinear FE model of a 22-day-old newborn EC and concluded that the newborn EC wall is not rigid, as assessed by tympanometry.…”