Anatoliy N. Ivakin
N. N. Andreev Acoust. Inst., Shvernika 4, Moscow 117036, Russia
A review of recent theoretical and experimental investigations of sound scattering from the seafloor and analysis of methods for remote acoustic characterization of marine sediments are presented. For narrow-band signals, echo characteristics have explicit relationships (in some simple cases they are known) to the reflection and scattering coefficients, which can be related in turn to the material parameters of the medium and used for determination of bottom properties. For wideband signals, the relations between the medium and conventional echo characteristics are not so evident. Moreover, one must introduce other characteristics, such as the two-frequency scattering function. Methods for the determination of bottom parameters in this case are not sufficiently studied up to now, but some advantages of wideband signals can be used such as their high spatial resolution and the possibility of their analysis in the time-frequency domain. The second aspect of the problem is connected with modeling the process of sound interaction with different bottom media. Several geoacoustic models for moderate to high frequencies are considered, taking into account regular sediment stratification and different types irregularity: roughness of the interfaces, volume inhomogeneities, and discrete scatterers.