Technical University of Clausthal TUC

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Coherent signal-based approach insolid
acoustic holography

• Technical University of Clausthal (TUC)
• Dr. G. Schäfer, W. Rolshofen

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Task 2.1 Wave propagation study and acoustic
holography in solid objects
New approach- using accelerometers

• In-solid method to improve S/N-ratio
  (interaction)
• Method leads real-life physical objects to become
  sensors
• Real-Time acoustic pattern localisation using
  in-solid holography technique
• Development of devices for validation of
  theoretical results

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Holography

• Superposition of Object and Reference Beam
• Plateholder saves Amplitude- and Phase-
  information Geometry
• Hologram Reconstruction

http//www.mit.edu/sdh/holography/eoh/index.html
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Purpose of Acoustic Holography
Reconstruction of wavefronts by their amplitude
and phase distribution
For Modelling of acoustic wave propagation in
solid objects

• Velocity of wave propagation
• Frequency of propagation mode

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Test equipment
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Experiments with plate of steel
Reference plate shipped by CeTT to all partners
to compare results within consortium
Due to dispersion, propagation velocity for plate
calculated by LOA
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Result for plate of steel
Source Localisation for 860Hz on a steel plate
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Wave propagation simulation
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Wave propagation simulation
Single- and multiple sources
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Outcome

• Study of wave propagation in-solids
• Mathematical description for NAH in-solids
• Development of a test rig
• Calculation of source localisation
• Improvement by dispersion function
• Correlation with tapping position for special
  frequencies
• Results for different kind of materials (steel,
  wood, glass)

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Future Tasks

• Improvement of accuracy by more sensors (UWC) and
  different arrangement
• Detection and localisation of multi-point sources
• Implementation of method into consortiums
  prototype (EyesWeb)