10 September 1987 A Transfer Function Model For Propagation In Homogeneous Media
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Proceedings Volume 0768, Pattern Recognition and Acoustical Imaging; (1987) https://doi.org/10.1117/12.940275
Event: International Symposium on Pattern Recognition and Acoustical Imaging, 1987, Newport Beach, CA, United States
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.
© (1987) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John Powers, John Powers, Daniel Guyomar, Daniel Guyomar, } "A Transfer Function Model For Propagation In Homogeneous Media", Proc. SPIE 0768, Pattern Recognition and Acoustical Imaging, (10 September 1987); doi: 10.1117/12.940275; https://doi.org/10.1117/12.940275
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