Brian Tracey
Henrik Schmidt
Dept. of Ocean Eng., MIT, 77 Massachusetts Ave., Bldg. 5-007, Cambridge, MA 02139
A self-consistent perturbation method for three-dimensional acoustic scattering due to sound-speed inhomogeneities has been developed. This method allows calculation of the mean-field attenuation due to scattering, as well as the second-order statistics of the reverberant field. Propagation in a shallow ocean overlying a sediment bottom containing sound-speed inhomogeneities is considered as an application. A modal expansion of the acoustic field is assumed and (mean-field) modal attenuation coefficients are calculated. The attenuation coefficient calculation is straightforward and is suitable for use with standard normal-mode codes. Numerical results show this work is consistent with an earlier approach to plane-wave scattering [D. Tang and G. Frisk, J. Acoust. Soc. Am. 90, 2751--2756 (1991)], and illustrate the importance of scattering into the continuous spectrum. The spatial correlation and intensity of the reverberant field in the waveguide are calculated. [Work supported by ONR High Latitude Program.]