| Acoustic normal mode propagation has been studied for a shallow, stratified ocean overlying an inhomogeneous, transversely isotropic porous sediment bed in the frequency range of 20-500 Hz. Biot's theory for poroelastic media has been used to model the anisotropic seabed. Both the shear and hydraulic (permeability) properties of the sediments are incorporated into a modified elastic model. The propagator matrix method has been utilized in the analysis to account for layer inhomogeneities and an impedance matching technique has been used as a criterion for eigenvalue convergence.; Laboratory measurements of geoacoustic parameters have been made for sediments of the Bahama Banks and the New Jersey shelf. The shear modulus and frame loss coefficients were measured using a combined torsional resonant column and triaxial apparatus. Permeability and porosity were measured using conventional sediment measurement techniques. This data has been used in the model to study the influence of sediment properties on dispersion and attenuation of acoustic waves. The sensitivity of the model to various seabed parameters has been examined numerically.; It has been found that the shear modulus, the permeability and the porosity are important seabed parameters for prediction of the acoustic wave attenuation, which in turn affects the transmission loss coefficient in shallow water. Also, the anisotropy in these properties have been shown to be important. |
