J. E. Sigurdson
Code 511, NCCOSC, RDT&E Div., 53405 Front St., San Diego, CA 92152-6530
The biosonar emissions of a free-swimming dolphin were measured with respect to direction and timing while the animal searched for and reported objects at various ranges and bearings from a test enclosure. The technology allows a quantitative description of the pulse-by-pulse scan pattern of the freely moving animal and subsequent inferences about search strategies, echo-integration time, functional beam coverage, and learning effects on biosonar performance. Presently, the methods are being extended to test an animal from a boat in the open ocean with measurement of the animal's attitude and movement in three dimensions as well as the spectral content of emitted pulses during search, detection, and discrimination. The technique combines standardized test paradigms, and instrumentation pack carried by the animal, and a positioning system. The animal's pack is a self-contained, data-acquisition system with sensors for magnetic azimuth, acoustic emissions, attitude, and motion. It is based on a high-speed, real-time microprocessor with open software architecture for maximum flexibility. The positioning system employs a high-accuracy real-time differential GPS for prepositioning targets and monitoring the position of the boat and animal during a search.