A two-wave-number description of shallow water ocean acoustics

Abstract

Wave-number spectrum is a useful measure of the spatial properties of the underwater acoustic field. A basic tenet of the wave-number spectrum approach is the spatial homogeneity of the cross-correlation (or cross-spectrum) function; a property that is frequently satisfied in deep water environments. Shallow water acoustic channels, on the other hand, are basically nonhomogeneous in the depth variable as a result of the addition of numerous normal modes or multipaths. Two-frequency spectrum have been used to analyze (temporal) nonstationary variables and to a lesser extent two-wave-number spectrum have found use investigating the nonhomogeneous noise in hydrophone array structures. For this paper, two-wave-number (vertical) spectrum were found for several canonical underwater acoustic waveguides. The physical significance of the results are identified by comparing them with similar spectrum from structural acoustic analysis. Particular attention is paid to the consequences of the nonhomogeneous structure to hydrophone array design and the channel parameters that emphasize the two-wave-number character of the spectrum. The sensitivity of the results to intermodal correlation suggests a measurement approach for determining this basic component correlation.