Three-dimensional finite element method (FEM) analysis of the middle
ear
The middle ear function is
important for sound transmission to the cochlea. However, the middle ear
dynamic characteristics are not easily measured by the conventional
impedance meters, and thus, the dynamic behavior of the middle ear has not
been well analyzed.
In our laboratory, based on the
measurement results of the computer assisted three-dimensional
reconstruction of human temporal bone (Fig.1), the FEM
model of the middle ear (Fig.2) has been established,
and using this model, its dynamic behavior is analyzed.
Figures 3 and 4 show the numerically obtained vibration patterns of the middle ear at
the frequencies of 0.5 kHz and 2.0 kHz, respectively. The differences in
the amplitude and phase of the tympanic membrane are demonstrated. Figures
5 and 6 show the vibration modes of
the ossicles view from the inferior. At the low frequency of 0.5 kHz, the
ossicles are rotating around the axis between the anterior
malleal ligament and the posterior incudal
ligament, and the umbo and stapes head have piston like movements. At
the frequency of 2.0 kHz, the axis of rotation lean and whirl, and the
umbo and stapes head have elliptical movements.
Currently, we intend to develop an optimal method of middle ear reconstruction
using this model.
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Fig.1. Three-dimensional reconstruction of human temporal
bone.
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Fig.2. FEM model of the middle
ear.
1, Tympanic membrane (pars tensa); 2, tympanic membrane (pars
flaccida); 3, malleus; 4, incus; 5, stapes; 6, anterior malleal ligament;
7, posterior incudal ligament; 8, tensor tympani tendon; 9, stapedial
tendon; 10, annular ligament.
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Fig.3.
Numerically obtained vibration pattern of the middle ear at 0.5 kHz.
Sound
pressure level at the tympanic membrane is 80 dB SPL. Displacement is magnified
7,000 times.
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Fig.4. Numerically obtained vibration
pattern of the middle ear at 2.0 kHz.
Sound pressure level at the tympanic
membrane is 80 dB SPL. Displacement is magnified 7,000 times.
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Fig.5. Numerically obtained vibration pattern of the ossicles at
0.5 kHz.
Displacement is magnified 30,000 times.
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Fig.6. Numerically obtained vibration pattern of the ossicles at
2.0 kHz.
Displacement is magnified 30,000 times.
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