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The characteristics of scattering due to interface roughness are usually described by the backscattering matrix for reverberation modeling. The backscattering matrix based on the Bass perturbation theory has significant differences from that based on the empirical scattering rule (Lambert's rule), especially at low grazing angles. In a waveguide environment with a point source, it is very difficult to extract the quantitative characteristics of the backscattering matrix at low grazing angles from the experimental data because of the difficulties in acquiring low-grazing-angle scattering data and separating the scattering data between different modes (grazing angles). In contrast, the use of single-mode excitations as sources in shallow-water waveguides enables acquisition of good quality low-grazing-angle scattering data. In this paper, the characteristics of the backscattering matrix were obtained from different single-mode reverberation experiments in shallow-water. The experiments were carried out at different sites during different seasons off the coasts of China. Model-data comparisons were made and the results showed that at low grazing angles (2 °-5 °), the backscattering matrices based on the Bass perturbation theory were in good agreement with the experimental data, but the backscattering matrices based on Lambert's rule were not. [ABSTRACT FROM AUTHOR]

Reflectivity measurements can be used in inversion techniques to obtain estimates of the physical characteristics of seabed sediments. In addition, computation of posterior probability distributions (PPDs) [S. E. Dosso, J. Acoust. Soc. Am. 111, 129–142 (2002)] provide an uncertainty of each parameter estimate obtained by a simulated annealing inversion. In this work, PPDs are calculated for experimental reflection loss data to evaluate the sensitivities associated with the parameters in the Biot-Stoll poro-elastic model for sediments. The data comes from a lab tank experiment in which reflection loss from a sandy sediment was measured as a function of grazing angle for frequencies between 75 kHz and 150 kHz. The sampling for the PPDs is based on the least-squares error between simulated reflection coefficient data and values modeled with the reflection module of OASES. [H. Schmidt, ‘‘OASES Version 2.1 User Guide and Reference Manual,’’ Department of Ocean Engineering, Massachusetts Institute of Technology, 1997.] The PPDs resulting from the lab data are compared with those obtained for simulated data, and the effects of experimental error on the results are explored. [ABSTRACT FROM AUTHOR]