Tursiops Biosonar Detection in Noise
Biosonar detection experiments conducted in the ocean are confounded as the range from the animal to the target is increased because added interference, such as fish schools, occlude the “field of view”. This experiment was designed to test deduction performance as a function of noise at a fixed range of 16.5 meters, thus reducing the range variability problem. Echolocation data were collected from two Tursiops truncatus, named Ehiku and Heptuna, in Kaneohe Bay, Hawaii, during November 1978. They were conditioned to respond discretely in a two alternative forced choice detection problem of 0.5 a priori random presence or absence of a 7.65 cm steel water-filled sphere (Ts. -32 dB). The sphere, displayed one meter below the surface and 16.5 meters from the porpoise at-scan station, assured stable low effort baseline detections in the absence of added noise. Detection accuracy, pulse train duration,., and response latency data were recorded in response-terminated trials. Five levels of white noise, 67, 72, 77, 82, 87 dB rel μPa in a 1 Hz band, were presented in 10 trial blocks, each level occurring twice in each 100 trial session. There were a minimum of 220 trials at each sound level. Ambient noise, which is extremely high in Kaneohe Bay, was about the same as the lowest white noise level used in the experiment.
KeywordsTrial Block Sound Level Ambient Noise Correct Detection Correct Rejection
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