Haitao Pan Shigeo Ohstuki
Precision and Intelligence Lab., Tokyo Inst. of Technol., Nagatsuta 4259, Midori-ku, Yokohama, 227 Japan
The Shell function method is presented as a new technique to evaluate the acoustic pressure field, produced by a practical source of finite area, in a medium having an arbitrary spatially varying sound speed. The Shell function method considers the acoustic wave received at the observation point, for a specified travel time, and the associated vibrating source area. In terms of ray representation, this approach is accomplished by interchanging the position of the observation point with that of the elemental area of the source. Both the convergent state of a sound beam issuing from the observation point, and the element area of the source responsible to this convergent state, are taken into account simultaneously. As a consequence, the sound pressure at, and in the vicinity of, caustics can be given an appropriate value directly. The Shell function method was evaluated by the computation of the acoustic field in a depth-dependent sound-speed profile containing caustics, for a linear source with a specified length.