Development of a 3-D Bioacoustic Imaging System

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The Marine Physical Laboratory at Scripps Institution of Oceanography will develop a sea-going, three-dimensional bioacoustic imaging system. The system addresses a long- standing requirement within biological oceanography to describe the distribution and interactions of small plank- tonic organisms in the open ocean. The use of nets and other acoustic devices are often inadequate in describing the distribution of organisms in certain scientifically important spatial and temporal scales. The imaging system is based on the principle of Spatially Variant Insonification, whereby spatial resolution in the water column relies on simultaneous transmission of discrete coded pulses along narrow acoustic beams. The reflection of these acoustic pulses, that are received at a single transducer, can then be deciphered from each other and an image is produced by complex mathematical processing. The system will operate at 500 kHz and will be designed to have a useful range of 50 meters within a 30- degree solid angle. At this frequency, the instrument will be sensitive to zooplankton and will be used to map and follow the distribution of these small organisms. A 3-D bioacoustic imaging capability will be useful to a number of envisioned research projects over the next decade. The new capability will provide information on the interactions and movements of the organisms within a volume of water.