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22 July 1997 Observation of buried object detection by a dolphin
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Acoustic buried object detection by a dolphin was observed by means of a hydrophone placed directly above the object. Dolphins are known to be adept at locating prey and objects that are buried in the sediment. This involves the detection and some level of identification of the prey. Since sediment is opaque, it is unlikely that vision is involved. It is likely that the dolphin uses sound to detect buried objects. Direct observation of the sound pulses arriving at the buried object provides information about the sound pulses employed by the dolphin. The observations show that the acoustic pulses are broad band, spanning the frequency range from a few tens of kilohertz to well over one hundred kilohertz. Modeling of the acoustic penetration of such a broad band pulse indicates that it will change shape as it is transmitted through the water-sediment interface. The change will depend on the sediment type and signal grazing angle. As the pulse penetrates into the sediment, it will undergo further distortion due to the frequency dependence of acoustic absorption. Acoustic penetration of the sediment has been modelled and the signal distortion may be expressed as a filter function, with certain characteristics, particularly a phase shift and a reduction at the higher end of the spectrum. These features provide an indication of whether a detected object is buried or not, and the depth of burial.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Nicholas P. Chotiros, Kenneth L. Krueger, Nathan S. Crow, and Robert A. Altenburg "Observation of buried object detection by a dolphin", Proc. SPIE 3079, Detection and Remediation Technologies for Mines and Minelike Targets II, (22 July 1997);

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