Finite Element Analysis of the Insertion Process of an Instant-Fit Earpiece in a Modeled Ear Canal
According to a World Health Organization report, more than 360 million people suffer from hearing loss [1]. The majority of patients can usually be fitted with conventional hearing aids. These devices are subject to continuous further development and optimization - connecting the performance to increasing expectations of the patients. Special interest is given, for example, to improving wearing comfort.
Hearing aids are equipped with earpieces, guiding the sound from the receiver toward the tympanic membrane. The focus of the present work is on devices worn behind the ear and having an external receiver in the ear canal and equipped with instant-fit earpieces. Usually, instant-fit earpieces for such devices are provided to the customer as soft silicone parts. Although, silicone earpieces are well accepted in the hearing aid market, they are suffering from two main limitations: The earpieces are often perceived to be uncomfortable to wear over a prolonged time and having a non-consistent acoustic performance, due to uncontrolled acoustic leakage. Both limitations are seen as a result of a non-ideal fit of the silicone earpieces in the complex shaped ear canal.
The overall objective of this work is to develop a better understanding of the mechanical interaction of a silicone dome in anatomically shaped ear canals by using finite element simulation. For this purpose and in a first approach, a simplified simulation model has been used approximating the ear canal by using a curved and solid tube representing the natural insertion process of an earpiece into a modeled ear canal.
By using COMSOL Multiphysics®, the CAD Import Module, Material Library and the Structural Mechanics Module with Multibody Dynamics add-on module, the prescribed displacement can be supplemented with a Cam-Follower enabling path tracking along a prescribed centerline.
The aim is to insert the instant-fit earpiece into the anatomically shaped ear canal along an irregularly curved centerline and to enable the earpiece to be positioned as realistically as possible. The final position of the earpiece allows extensive evaluation of contact pressure, contact length and high deformation due to the soft silicone earpiece. The generated results should be used for the further development of an optimized silicone earpiece towards increased wearing comfort and better controlled acoustic properties.
References
[1]. WHO/NMH/PBD, Millions of people in the world have hearing loss that can be treated of prevented, 2013
