Comparison of Seafloor Roughness and Scattered Acoustic Temporal Decorrelation

Connecting changes in acoustic scattering from the seafloor with changes in seafloor topography is essential for modeling the time dependence of the scattering and the development of acoustics as a tool for the remote sensing of benthic activity. An equation is derived that links the decorrelation of scattered acoustic power with the decorrelation of seafloor roughness spectral estimates. The result is assessed through a comparison of decorrelation values generated by processing topographical data recorded by a digital photogrammetry system and backscattering data acquired with a translating source/receiver assembly. Both data sets were collected off the western coast of Florida as part of the U.S. Office of Naval Research (ONR)-sponsored sediment acoustics experiment (SAX04), during which the primary mechanism of topographical change at the frequencies of interest appeared to be fish feeding. Although decorrelation curves proved to be both space and time dependent, and the collection of data sets was neither collocated nor synchronized, the agreement between averaged topographical and acoustic decorrelation values was reasonable. Both types exhibited a strong frequency dependence, which should prove beneficial in classifying and quantifying sources of seabed transformation if it is mechanism specific.