Optomechanical measurement and FE modeling of tympanic membrane mechanics

Jef AernoutsLaboratory of Biomedical Physics (BIMEF)University of Antwerp

Presentation at Philips Group InnovationOctober 5, 2012

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Optomechanical measurement and FE modeling of tympanic membrane mechanics

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The human ear

tympanic

membrane

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Function of the ear

Convert sound (20-20000 Hz) > nerve activity in our brain

What is role middle ear?

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Why study TM mechanics?

• Middle ear finite element modeling

normal

diseasedreconstructed

tympanic membrane!

(Aerts J, Aernouts J. 2012)

(Gan et al., 2009)

(Kelly et al., 2003)

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Outline

1. Tympanic membrane elasticity

2. Tympanic membrane vibrations

3. Middle ear modeling

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Outline

1. Tympanic membrane elasticity

2. Tympanic membrane vibrations

3. Middle ear modeling

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Human tympanic membrane

- Base diameter: 9 mm- Apex height: 1.7 mm

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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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Needle indentation

• Approach- Apply indentations- Measure forces

• Sample preparation

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Needle indentation

• Approach- Apply indentations- Measure forces

• Sample preparation

• Shape measurement

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Needle indentation

• Approach- Apply indentations- Measure forces

• Sample preparation

• Shape measurement

• Finite element model

In rest

Indented

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Needle indentation

• Approach- Apply indentations- Measure forces

• Sample preparation

• Shape measurement

• Finite element model- Fit experiments

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Outline

1. Tympanic membrane elasticity

2. Tympanic membrane vibrations

3. Middle ear modeling

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TM vibrations

• Sample

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TM vibrations

• Sample

• Stroboscopic holography- Sounds: 0.5 kHz –

19 kHz, 80-120 dB- Full-field displacement

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• Principle

Holography

CCD

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• Principle

• Stroboscopic holography

Holography

sample

holography setup

speaker

probe microphone

camera

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FE model

• Geometry (from micro-CT)• Boundary conditions & Loadings

sound wave

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TM full-field displacement

- Measured with stroboscopic holography:

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TM full-field displacement

- Measured with stroboscopic holography:- Finite element outcome

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Outline

1. Tympanic membrane elasticity

2. Tympanic membrane vibrations

3. Middle ear modeling

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Middle ear FE model results

1000 Hz

(x8e3)

7000 Hz

(x3e4)

16000 Hz

(x2e5)

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Thanks for your attention!

• Questions? I’m all ears…

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TM curvature

• Cochlear load at umbo (tip malleus)• Natural curved versus artificially flat

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TM curvature

• Umbo velocity response800 Hz – 4 kHz:

17.5 dB difference