ASYMPTOTIC ANALYSIS OF ACOUSTIC FIELD BY GEOMETRICAL-THEORY OF DIFFRACTION IN ANTIWAVEGUIDE PROPAGATION

The asymptotic analysis of the antiwaveguide propagation of sound waves in continuously layered media is described. The geometrical theory of diffraction developed by Keller and collaborators is extended to account for the sound fields in the transition region near the limiting ray that grazes the sea surface. Included are normal-modes, acoustical rays and diffracted rays. Numerical comparisons with the normal-mode solution reveal the validity and utility of the asymptotic analysis studied in the present paper. The diffracted ray solution applied in the transition region near the geometrical shadow zone is the most satisfactory from the physical viewpoint.