![]() This is particularly evident in the eardrum. The animations of the oscillations of the middle ear structures at different frequencies clearly show, however, that the movement patterns are frequency-dependent. When solely regarding one METF it slightly suggests that there is only one form of movement in the middle ear. the first resonance of the middle ear lies individually between 800-1000 Hz. The resonance characteristic of the middle ear is lost with this averaging, since e.g. When comparing the middle ear transfer function (METF) with the experimental data, it should be noted that these mean values represent many different middle ears. The left diagram shows that the TF of the simulation model lies within the range of the transfer function of normal middle ears. 100-6000 Hz, as well as sound pressure levels up to max. From a medical therapeutic point of view, the speech frequency range, being approx. The amplitude frequency response of the TF is shown with a logarithmic or dB scale, as this offers the best comparison with the audiological examination results. In doing so, it is assumed that the movement of the stapes footplate in the normal direction is the essential component for the sound transmission to the inner ear fluid. The most commonly used TF accounts for the normal displacement or velocity of the stapes footplate to the sound pressure at the entrance of the auditory canal or in front of the eardrum. The function of the middle ear is essentially assessed using transfer functions (TF). Model simulation for middle ear physiology The material parameters of the model were adjusted by comparison with experimental studies on specimens. The geometry of the model correlates to an average middle ear. The inner ear is approximated by a single-mass-spring-damper system. The air volume of the tympanic cavity is not taken into account (influence < 5 dB). At the entrance to the auditory canal, a boundary condition of type 3 (matched impedance) is realized. The volume of the auditory canal is depicted as a compressible, lossless fluid and is connected to the eardrum via a fluid-structure coupling. The ligaments are rotationally symmetrical beams with isotropically elastic material behaviour. The hammer-anvil articulation and the anvil stirrup joint are represented as a homogeneous isotropic viscoelastic material with 20 knot volume elements. The ossicles are each represented by a rigid framework with a mass point element in the center of gravity in which all inertial properties are concentrated. The eardrum is described as a multi-layered, thin, double-curved shell with orthotropic viscoelastic material properties. The simulation model was devised with the help of the Finite Element Method (FEM) (program package ANSYS). Without the middle ear, hearing perception would be approximately 30-40 dB worse, which would translate to loud colloquial speech then only being perceived as whispering. This is essentially achieved by the area ratio between the eardrum and the stapes footplate. The fundamental function of the inner ear is the impedance adjustment between the air and the inner ear fluid. ![]() The conversion of fluid oscillations into an electrical signal, needed for the acoustic nerve occurs by the hair sensory cells in the inner ear. The eardrum absorbs the sound conducted through the air coming from the auditory canal, the ossicles transfer the oscillations to the stapes footplate, where they are transmitted to the inner ear fluid (perilymph). It encompasses the eardrum and the three auditory ossicles (ossicles), hammer, anvil and stapes. The middle ear connects the inner ear with the auditory canal. The experiments on temporal bone preparations that have been necessary to date are to be replaced with this method, while simultaneously improving middle ear reconstruction. Further, the model is used to simulate reconstruction methods, replacement materials, prostheses and implantable hearing systems for the middle ear on the computer and to optimize them through variations. ![]() ![]() With the model’s help, information on the functioning of the middle ear can be obtained in detail and depicted visually. The simulation model of the human middle ear is a mathematical model based on the Finite Element Method (FEM). ![]()
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