Using Buried Directional Receivers in High- Frequency Seafloor Studies

Knowledge of acoustic arrival angle can be useful for studying penetration mechanisms and for estimating sediment sound speed dispersion. The arrival angle of the acoustic field penetrating the water-sediment interface, however, is difficult to measure using sparsely distributed pressure sensors. The arrival angle, as well as amplitude information, can be unambiguously obtained by measuring particle motion with directional receivers. An experiment was conducted off of Elba Island, Italy, to assess the feasibility of a novel technique that uses high-frequency accelerometers to measure the directionality of acoustic arrivals. Measurements of acoustic penetration into a sandy seafloor were obtained over a wide frequency range (2.5 to 29 kHz) using off-the-shelf accelerometers, adapted for use in marine studies. The sensors that were developed are suitable for the penetration studies for which they were devised, but their angular resolution would limit their application in dispersion studies. Insights from this experiment will guide the design of new directional sensors that are suitable to study dispersion.