Abstract
Like any antenna, bat pinnae have directivity patterns which impose a frequency-dependent sensitivity weighting on possible locations of sonar targets. Here, numerical predictions of such directivities are presented. The predictions are based on finite-element meshes generated from computer-tomographic cross-section images of pinna samples obtained from several bat species. A time-domain finite-element model was combined with a near-field to far-field transformation to yield high-resolution directivity estimates. The data obtained enable the introduction of new visualization approaches to the study of bat biosonar. These techniques portray the spatial and frequency dimension of the patterns, facilitate quantitative analysis, and reveal functional properties relevant to specific sensing tasks, like scanning the surface of an extended target. The computer graphics representations of the pinna shapes (voxel arrays, volume and surface meshes) can be readily manipulated to shed light onto how the observed properties arise. For example, appendages have been removed by ‘‘Boolean surgery’’ or altered in orientation or shape by standard computer graphics transformations. The results of these manipulations are compared with respect to wave-field amplitudes as well as with respect to directivity patterns. [Work supported by the European Union (CIRCE Project, IST-2001-35144).]
Published Version
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