Nataly A. Sidorovskaia
Dept. of Phys., Univ. of New Orleans, New Orleans, LA 70148
Michael F. Werby
Naval Res. Lab., Stennis Space Center, MS 39529
Broadband pulse propagation through an oceanic sound channel is investigated to characterize some important oceanic properties, namely, the vertical sound profile, bottom structure, and also source localization. Examples of waveguides with surface and bottom ducting are considered. The new fast normal mode method (SWAMP) based on a new expansion method allows one to study the high frequency range in which large numbers of modes can be excited. In this situation the complicated structure of the wavefront that is the result of the interference of the low-order trapped refractive modes and the high-order reflected modes is observed in the waveguides. To understand the structure of this informatively rich wavefront, two techniques are presented: The static spatial-time maps of the sound field intensity distribution in a waveguide and video movies permitting one to observe the time evolution of a pulse through the fixed spatial region. The later technique gives much additional information on the process and can offer additional insight into the nature of pulse evolution along a waveguide. [Work sponsored by the Office of Naval Research.]