Title page for ETD etd-12222010-233428


Type of Document Master's Thesis
Author Balakrishnan, Sreenath
Author's Email Address bsreenat@vt.edu
URN etd-12222010-233428
Title A Numerical Elastic Model for Deforming Bat Pinnae
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Mueller, Rolf Committee Chair
Priya, Shashank Committee Member
Socha, John J. Committee Member
Keywords
  • bat pinnae
  • Deformable models
  • ear movements
  • spatial hearing
  • biosonar
Date of Defense 2010-12-10
Availability unrestricted
Abstract
In bats, the directivity patterns for reception are shaped by the surface geometry of the pinnae. Since many bat species are capable of large ear deformations, these beampatterns can be time-variant. To investigate this time-variance using numerical methods, a digital model that is capable of representing the pinna geometry during the entire deformation cycle has been developed.

Due to large deformations and occlusions, some of the surfaces relevant to sound diffraction may not be visible and the geometry of the entire pinna has to be computed from limited data. This has been achieved by combining a complete digital model of the pinna in one position with time-variant sparse sets of three dimensional landmark data. The landmark positions were estimated using stereo vision methods. A finite element model based on elasticity was constructed from CT scans of the pinna post mortem. This elastic model was deformed to provide a good fit to the positions of the landmarks and retain values of smoothness and surface energy comparable to life. This model was able to handle ratios of data to degrees of freedom around 1:5000 and still effect life-like deformations with an acceptable goodness of fit.

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