Influence of the Auditory System on Pressure Distribution in the Ear Canal

Abstract

The pressure gain distribution along the ear canal is strongly dependent on boundary conditions, and, in normal conditions, the ear canal produces a 0–20-dB pressure gain close to the tympanic membrane in the 0.1–20[Formula: see text]kHz range. Additionally, the pressure gain distribution along the ear canal at high frequencies (over the second resonance of the ear canal at 8–9[Formula: see text]kHz) depends strongly on axis position; therefore, the middle ear transfer functions based on ear canal pressure are also strongly dependent on the measuring point. Objective: The aim of this study is to evaluate the mechanical influence of the tympanic cavity, ossicular chain and tympanic membrane connections on the pressure in the ear canal in the frequency range of 0.1–20[Formula: see text]kHz when a pressure source is applied to the ear canal entrance. Methods: We have developed numerical simulations for seven different models using the finite element method (FEM). Starting with an external ear canal finite element model, additional elements are coupled or removed to evaluate their contributions. We modeled and simulated the tympanic membrane, ossicular chain, tympanic cavity and a simplified cochlea in seven different combinations. Results: The pressure distribution along the external ear canal is obtained and represented in the 0.1–20[Formula: see text]kHz range for the seven model configurations.

Analysis of the Mechanical Properties of the Human Tympanic Membrane and Its Influence on the Dynamic Behaviour of the Human Hearing System

“…The small element size used in this model to mesh the TM captures these modes very accurately. At this frequency range, the absence of the ossicular chain has a reduced influence [ 18 , 19 ], so for the purpose of the present study, this simplified model is acceptable. As a rule of thumb for the interpretation of the following figures, mode 5 may represent the transition to complex pattern and mode 15 the transition to ordered pattern.…”

“…Some recent numerical models include this acoustic effect ([ 15 , 17 – 19 ]), but even in this case, the condition in which the experiment was made may show significant differences, making the comparison limited. Different conditions on the experiment as the position of the source of sound [ 31 , 32 ] or the presence of cavities open or closed lead to different responses of the same mechanical system.…”

“…The alternative is numerical simulation. Since the early works led by Funnell and Laszlo [ 6 ] and Funnell et al [ 7 , 8 ], finite element (FE) models have been used to study the behaviour of the system [ 9 – 19 ]. Nevertheless, uncertainties regarding the accuracy of the material properties hinder the numerical simulation and limit the extension of the conclusions.…”

Numerical model characterization of the sound transmission mechanism in the tympanic membrane from a high-speed digital holographic experiment in transient regime

“…Since the first works on numerical models on cats’ eardrums [ 21 , 22 ] or on the behavior of the middle ear in humans [ 23 , 24 ], finite element models (FEMs) of the auditory system have evolved considerably [ 25 – 28 ] The three-dimensional finite element models of the auditory system make it possible to represent complex geometry of the ear more accurately [ 25 , 26 , 28 – 30 ]. Great efforts have been made to determine realistic material properties of middle ear structures represented in the model [ 29 , 31 – 35 ]. Other approach is to focus on main physical phenomena implied in the process using simplified models.…”

Measuring Absorbed Energy in the Human Auditory System Using Finite Element Models: A Comparison with Experimental Results

“…In this current article, we used assumed values for these components without attempting to discuss their accuracy. We simulated different combinations to discern the impact of each subsystem in the human auditory system (AS), building on a previous paper with a similar methodology [39] that determined how the AS influences pressure distribution in the EAC.…”