Grant B. Deane
Marine Phys. Lab. 0238, Scripps Inst. of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0238
In recent years there has been an increasing interest in developing analytical solutions to various range-dependent, three-dimensional propagation problems. Calculation of the sound field from a point source in a homogeneous wedge is such a problem. However, although interesting, the wedge is not representative of the geometry of many shallow water channels. Over continental shelf and slope regions, the bottom is often faceted, that is to say, the channel can be represented as a ``hybrid duct'' constructed from two or more planar boundaries. The wedge (two planes) and a parallel-sided duct terminated by a wedge (three planes) are examples of hybrid ducts. A technique has been developed for evaluating the field in a hybrid duct with perfectly reflecting boundaries. The new method is based on a novel extension of the method of source images, in which the concept of an image is abstracted into a set of generating sequences and a visibility criterion. A solution will be presented for the sound field in a duct terminated by a wedge as an example of this technique. The method is exact provided the diffracted component of the sound field is negligible. A description of how the source-image approach can be extended to hybrid ducts with penetrable boundaries will be given.