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Proceedings Paper

A Transfer Function Model For Propagation In Homogeneous Media
Author(s): John Powers; Daniel Guyomar
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Paper Abstract

Diffraction effects are important in acoustic imaging and tissue characterization because of the relatively large wavelengths used and the fact that applications are frequently used in the near-field of the source. It is difficult to intuitively anticipate the shape of the field there, yet the description of the field's spatial acoustic potential or pressure distribution is necessary. This problem is more complicated when focused transdu-cers or phased arrays are used. Using the spatial frequency, domain it is possible to model propagation in lossless and lossy media as a transfer function. The sources are represented as planar sources with separable arbitrary time excitation and arbitrary spatial excitation. Transfer functions can be obtained for lossless media, media with a linear frequency dependence of attenuation coefficient, and media with a quadratic dependence of attenuation co-efficient. The transfer functions are shown to be simply related to the two-dimensional spatial transform of the Green's function of the wave equation for propagation in the medium of interest with the assumed boundary conditions. The transfer functions of the lossy and lossless propagation models are shown to be interdependent. For any given observation plane, these transfer functions are time-varying spatial filters that attenuate higher spatial frequencies with increasing effectiveness as time proceeds. The effects of source excitation and apodization, source boundary conditions, assumed media properties, and receiver aperture effects are easily incorporated in this model. Several numerical simulations of computed acoustic potentials and pressure distributions are shown.

Paper Details

Date Published: 10 September 1987
PDF: 7 pages
Proc. SPIE 0768, Pattern Recognition and Acoustical Imaging, (10 September 1987); doi: 10.1117/12.940275
Show Author Affiliations
John Powers, Naval Postgraduate School (United States)
Daniel Guyomar, Schlumberger-EPS (France)

Published in SPIE Proceedings Vol. 0768:
Pattern Recognition and Acoustical Imaging
Leonard A. Ferrari, Editor(s)

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