This document summarizes research on measuring and modeling the mechanics of the human tympanic membrane (eardrum). Needle indentation experiments were used to measure the elastic properties of TM samples. Stroboscopic holography captured the full-field vibrations of the TM under sound stimulation. A finite element model of the TM was developed based on its geometry and boundary conditions. The model results matched experimental vibration measurements and showed the importance of the TM's natural curvature for normal hearing function.

1. Optomechanical measurement and FE modeling
of tympanic membrane mechanics
Jef Aernouts
Laboratory of Biomedical Physics (BIMEF)
University of Antwerp
Presentation at Philips Group Innovation
October 5, 2012

2. Optomechanical measurement and FE modeling
of tympanic membrane mechanics
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3. The human ear
tympanic
membrane
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4. Function of the ear
Convert sound (20-20000 Hz) > nerve activity in our brain
What is role middle ear?
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5. Why study TM mechanics?
• Middle ear finite element modeling
tympanic membrane!
normal
(Aerts J, Aernouts J. 2012) reconstructed
diseased (Kelly et al., 2003)
(Gan et al., 2009)
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6. Outline
1. Tympanic membrane elasticity
2. Tympanic membrane vibrations
3. Middle ear modeling
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7. Outline
1. Tympanic membrane elasticity
2. Tympanic membrane vibrations
3. Middle ear modeling
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8. Human tympanic membrane
- Base diameter: 9 mm
- Apex height: 1.7 mm
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9. Needle indentation
• Approach
- Apply indentations
- Measure forces
(1) TM, (2): force transducer,
(3): piston, (4): LVDT , (5): signal
generator, (6): feedback control unit
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10. Needle indentation
• Approach
- Apply indentations
- Measure forces
• Sample preparation
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11. Needle indentation
• Approach
- Apply indentations
- Measure forces
• Sample preparation
• Shape measurement
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12. Needle indentation
In rest
• Approach
- Apply indentations
- Measure forces
• Sample preparation
Indented
• Shape measurement
• Finite element model
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13. Needle indentation
• Approach
- Apply indentations
- Measure forces
• Sample preparation
• Shape measurement
• Finite element model
- Fit experiments
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14. 13

15. Outline
1. Tympanic membrane elasticity
2. Tympanic membrane vibrations
3. Middle ear modeling
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16. TM vibrations
• Sample
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17. TM vibrations
• Sample
• Stroboscopic holography
- Sounds: 0.5 kHz –
19 kHz, 80-120 dB
- Full-field displacement
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18. Holography
• Principle
CCD
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19. Holography
• Principle
• Stroboscopic holography
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20. probe microphone
speaker
holography setup
sample
camera

21. FE model
• Geometry (from micro-CT)
• Boundary conditions & Loadings
sound wave
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22. TM full-field displacement
- Measured with stroboscopic holography:
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23. TM full-field displacement
- Measured with stroboscopic holography:
- Finite element outcome
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24. Outline
1. Tympanic membrane elasticity
2. Tympanic membrane vibrations
3. Middle ear modeling
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25. Middle ear FE model results
1000 Hz 7000 Hz 16000 Hz
(x8e3) (x3e4) (x2e5)
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26. Thanks for your attention!
• Questions? I’m all ears…
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27. TM curvature
• Cochlear load at umbo (tip malleus)
• Natural curved versus artificially flat
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28. TM curvature
800 Hz – 4 kHz:
• Umbo velocity response 17.5 dB difference
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