Target detection in noise by echolocating Atlantic bottlenose dolphins

Abstract

The capability of two echolocating Atlantic bottlenose dolphin (Tursiops truncatus) to detect a target in the presence of white noise was investigated. The target was a 7.62-cm-diam water-filled sphere located at a range of 16.5 m. A spherical transducer located 4 m from the animal directly in line with the target was used to project noise into the water; the spectrum of the projected noise was relatively flat from 40 to 160 kHz. The dolphins’ target detection performance as a function of noise level was determined. At the 75% correct response threshold, which was estimated by interpolation, the echo signal-to-noise ratio was 7.4 dB for one animal and 12.8 dB for the other. The response of an ideal energy detector was found to match the behavioral results as a function of the echo signal-to-noise ratio. It was observed that the dolphins’ response bias departed from the Neyman–Pearson criterion generally associated with dolphin echolocation experiments.