Geoacoustic inferences from seabed reflection measurements on the New England mud patch

The vast majority of sediment acoustics research has been aimed at understanding propagation in granular (sandy) sediments. The focus of the ONR Seabed Characterization Experiment was to improve understanding of fine-grained/cohesive sediments. A variety of measurement techniques by various researchers were conducted to that end. Here, we report on initial results from broadband wide-angle reflection measurements at two sites, one with a ∼2 m “mud” layer thickness and the other ∼11 m thick. The measured reflection coefficient exhibits features that permit estimation of geoacoustic properties including the critical angle (with a rather weak frequency dependence, 200-2500 Hz) and interference patterns in frequency-angle space (which provide information on properties in individual layers). Modeling permits insight into the information content of the data and some initial estimates of the geoacoustic properties. [This research was funded by the Office of Naval Research, Ocean Acoustics Program.]