Target Detection in Noise by Echolocating Dolphins

It is well known that dolphins possess a sonar capability which allows them to project acoustic energy and analyze returning echoes in order to detect and recognize objects under water. The use of acoustic energy is probably the most effective way to probe an underwater environment for purposes of navigation, obstacle avoidance, prey and predator detection, and object localization and detection. Acoustic and other mechanical vibrational energy propagates in water more efficiently than any form of energy including electromagnetic, thermal and optical energy. Since the natural habitats of many dolphin species include shallow bays, inlets, coastal waters, swamps, marshlands, and rivers that are often so murky or turbid that vision is severely limited, these animals must rely heavily on their active and passive sonar capabilities for survival. Some of the sonar capabilities of dolphins have been described in review articles by Nachtigall (1980) and Au (1988).