ASA 127th Meeting M.I.T. 1994 June 6-10

4pUW11. Scalar measures of modal amplitude distributions in range-dependent waveguides.

B. J. Orchard

D. K. Cooper

U.S. Naval Res. Lab., Code 7127, Washington, DC 20375

In a shallow water waveguide with a depth-dependent sound velocity profile, the short-range modal amplitude distribution depends strongly upon the sound-speed profile at the source. At sufficiently high frequency, a source in the high-velocity portion of the water column excites primarily the higher-order modes while a source in the lower-velocity portion of the water column couples more strongly with the lower-order modes. Scalar measures, such as the correlation, cross-entropy and information divergence are used in this paper to differentiate between different modal amplitude distributions by projecting the cross-spectral density matrix (CSDM) onto the eigenvectors of a baseline CSDM. Environmental features which cause mode coupling (e.g., bottom slope) diminish the effectiveness of these measures. The robustness of these scalar measures in the presence of the mode coupling is examined. [Work sponsored by Office of Naval Research, Code 4530.]