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PULSED CREEPING WAVES IN ACOUSTICS.
Rept. on Underwater Acoustics Program,
CATHOLIC UNIV OF AMERICA WASHINGTON D C
Pagination or Media Count:
The phenomenon of diffraction of acoustic and electromagnetic waves by finite or semi-finite obstacles has been interpreted, mainly following the classical paper by Franz, in terms of damped waves which, starting out at the boundary of the geometrical shadow, encircle the body any number of times creeping waves. In acoustics, the sound velocity is small enough so that with sound pulses of sufficiently short duration, the individual creeping waves may be followed around the obstacle directly, whereas in the electromagnetic case, only steady-state interference effects can mainly be observed. The present work is a study of the diffraction of plane-wave sound pulses of arbitrary shape, including their geometrical reflection from the vertex, and their propagation on both the shadow and the insonified surface of the body, as well as their observation at large distances. The special example of an infinitely long, acoustically soft circular cylinder of not too small radius is used, but an extension to other simple cases is possible. Author
APPROVED FOR PUBLIC RELEASE