Christian de Moustier
Daniel Sternlicht
Marine Phys. Lab., Scripps Inst. of Oceanogr., 9500 Gilman Dr., La Jolla, CA 92093-0205
A monostatic temporal model of seafloor acoustic backscatter has been
developed to investigate the relative contributions of interface roughness and
inhomogeneities in the sediment volume for measurements made at various angles
of incidence. The model takes into account sonar parameters such as acoustic
wavelength, beam pattern, pulse length, and angle of incidence, and it includes
a theoretical angular dependence of seafloor scattering strength that is
controlled by the roughness statistics of the surface insonified, by its
refraction index, and by a volume reverberation term. Simulations have been
carried over angles of incidence from 0(degrees) to 60(degrees), and at
acoustic frequencies ranging from 10 to 100 kHz for various types of
substrates. The theoretical angular dependence predicts that the contribution
from the sediment volume becomes noticeable for angles of incidence greater
than about 6(degrees); however, in the temporal model it is shown that this
contribution can be detected closer to normal incidence for small beamwidths
(e.g., 2(degrees)). When applied to a multi-narrow-beam sonar geometry this
temporal model shows greater potential for bottom classification than the
angular dependence function of acoustic backscatter obtained by integrating the
returns received in each beam. [Work supported by ONR.]