Semi-automatic algorithm to build finite element numerical models of the human hearing system from Micro-CT data

Abstract Finite Element modeling has been an extended methodology to build numeri- cal model to simulate the behavior of the hearing system. Due to the complex- ity of the system and the difficulties to reduce the uncertainties of the geometric data, they result in computationally expensive models, sometimes generic, representative of average geometries. It makes it difficult to validate the model with direct experimental data from the same specimen or to estab- lish a patient-oriented modeling strategy. In the present paper, a first attempt to automatize the process of model building is made. The source information is geometrical information obtained from CT of the different elements that compose the system. Importing that data, we have designed the complete pro- cedure to build a model including tympanic membrane, ossicular chain and cavities. The methodology includes the proper coupling of all the elements and the generation of the corresponding finite element model. The whole auto- matic procedure is not complete, as we need to make some human-assisted decisions; however, the model development time is reduced from 4 weeks to approximately 3 days. The goal of the modeling algorithm is to build a Finite Element Model with a limited computational cost. Several tasks as contour identification or model decimation are designed and integrated in order to fol- low a semi-automated process that allows generating a patient-oriented model.Funding for open access charge: Universidad de Málaga / CBU

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

The difficulty to estimate the mechanical properties of the tympanic membrane (TM) is a limitation to understand the sound transmission mechanism. In this paper, based on finite element calculations, the sensitivity of the human hearing system to these properties is evaluated. The parameters that define the bending stiffness properties of the membrane have been studied, specifically two key parameters: Young’s modulus of the tympanic membrane and the thickness of the eardrum. Additionally, it has been completed with the evaluation of the presence of an initial prestrain inside the TM. Modal analysis is used to study the qualitative characteristics of the TM comparing with vibration patterns obtained by holography. Higher-order modes are shown as a tool to identify these properties. The results show that different combinations of elastic properties and prestrain provide similar responses. The presence of prestrain at the membrane adds more uncertainty, and it is pointed out as a source for the lack of agreement of some previous TM elastic modulus estimations

An efficient strategy for modeling the human auditory system from Micro-Computed Tomography Imaging.

Finite Element modeling is a widely used methodology to build numerical models and simulate the behavior of the human auditory system; this has allowed essential advances in understanding the biomechanics of that complex system. There are two key points in modeling: the construction of an adequate geometry that allows efficient meshing and the correct use of mechanical properties of the materials. This research aims to show a new strategy for automating the build Finite Element Model process of the human auditory system using the FEM from Micro-Computed Tomography (Micro-CT) Imaging. The idea behind this methodology is to build a Finite Element Model with a computational and temporal low cost. This work allowed us to design the first semi-automatic algorithm to build a finite element model of the human middle ear that will later be used to incorporate the other components of the auditory system for different types of studies.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Advances in the determination of the mechanical properties of thin membranes through dynamic tests

El editor de las actas del Congreso da permiso para poner el texto completo en el repositorio institucional de la uma.The mechanical properties of thin membranes can be determined by non-destructive dynamic tests. When a membrane is subjected to sound pressure, it vibrates according to its natural modes. These vibration modes depend directly on their mechanical characteristics, including Young's modulus. The interaction between sound waves and the membrane (mechanical-acoustic coupling) is complex and requires a thorough study: For this reason, it is necessary to evaluate different aspects that influence in the natural frequencies present in the response. Among these parameters are: the position of the sound source, the measurement points, the geometry and dimensions of the material, the frequency range or the quantities to be measured, among others. This work presents the first results of a new case study with more data of excited frequencies and measurement points, to improve the precision of the results obtained.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Análisis de parámetros críticos en la configuración de un ensayo no destructivo para membranas

Copyright de los autoresEn este trabajo se analizan los distintos parámetros a determinar en la configuración de un ensayo dinámico no destructivo, cuya finalidad es obtener las propiedades mecánicas de membranas delgadas. Los ensayos tradicionales, algunas veces resultan no adecuados para estos materiales, por tratarse de ensayos destructivos o por utilizar materiales adicionales. Una alternativa a estos ensayos es la elección de un ensayo vibro-acústico no destructivo. Cuando una membrana delgada es sometida a una presión sonora, en ésta se genera una respuesta dinámica función de los modos de vibración de la misma. Se trata de un problema complejo, donde la relación entre las ondas sonoras y la respuesta de la membrana no es fácil de determinar, y requiere un estudio en profundidad para poder obtener esa interacción. Por este motivo es necesario estudiar los parámetros que influyen en la respuesta dinámica de la membrana, para tener la respuesta lo más determinada y acotada posible. Entre los parámetros a estudiar se pueden destacar: la posición de la fuente de sonido, la geometría y dimensiones de la membrana, los puntos a medir, el rango de frecuencias, entre otros. El estudio de estos parámetros es fundamental para determinar la configuración del ensayo dinámico.Campus de Excelencia Internacional Andalucía Tech