Cylinder Wall Thickness Difference Discrimination by an Echolocating Dolphin.

摘要

The capability of an Atlantic bottlenose dolphin to discriminate wall thickness differences of hollow cylinders by echolocation was studied. A standard cylinder of 0.635-cm wall thickness was compared with cylinders having wall thickness that differed from the standard by + or - 0.2, + or - 0.3, + or - 0.4, and 0.8 mm. All cylinders had an o.d. of 3.81 cm and a length of 12.7 cm. The dolphin was required to station in a hoop while the standard and comparison targets, separated by an angle of + or - 11 deg from a center line, were simultaneously presented at a range of 8m. The dolphin was required to echolocate and indicate on which side of the center line the standard target was located. Target location on each trial was randomized. The dolphin could discriminate will thickness differences of -0.23 and +0.27 mm at the 75% correct response threshold. Results of backscatter measurements suggest that if the dolphin used time domain echo cues, it may be able to detect difference in the time between two echo highlights to within approximately + or - 500 ns. If the dolphin used frequency domain cues, it may be able to detect frequency shifts as small as 3 kHz in broadband echoes having a center frequency of approximately 110 kHz.