Discrimination of phantom targets by an Atlantic bottlenose dolphin (Tursiops truncatus)

Abstract

The ability to make fine distinctions in properties of targets is one of the outstanding characteristics of the dolphin sonar system. Behavioral experiments with these animals can reveal target echo features that can be used to model the biological sonar in order to evolve technical systems with equivalent capabilities. A phantom echo generator was developed in order to obtain programmable control over echo parameters in the time and frequency domains. Dolphin sounds are recorded with a hydrophone, transformed into the desired phantom echoes, and played back with a projector hydrophone. The signal transformation is based on the acoustic impulse response of a target and is executed on a DSP system in real time. In the first experiment the capability of a dolphin to discriminate between acoustically simulated phantom replicas of targets and their real equivalents was tested. Phantom replicas were presented in a probe technique during a materials discrimination experiment. The animal accepted the phantom echoes and classified them in the same way as it classified real targets.