ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

4pUW12. Determination of seabed statistical properties and their effects on acoustic wave propagation in shallow water.

Altan Turgut and par Stephen N. Wolf

Naval Res. Lab., Acoust. Div., Washington, DC 20375

Genetic algorithms are used to invert statistical properties of sea bottom/sub-bottom from backscattering data. Backscattering from the seabed is calculated using composite roughness model of Jackson et al. [J. Acoust. Soc. Am. 79(5) (1986)], incorporated with the volume scattering model of Stockhausen [NRE Report 63/9 (1963)]. A parametric study indicates that, for given average sound speed and density of the seabed, bottom roughness parameters such as spectral strength and spectral exponent and sub-bottom parameters such as sound-speed variation, vertical correlation length, and horizontal correlation length can be inverted successfully. Complementary sub-bottom measurement techniques such as core sampling, seismic, and tomographic measurements are also discussed. Acoustic calculations using measured seabed inhomogeneities predict significant coupling to the higher-order modes. This coupling manifests itself as an important loss mechanism.