No abstract

Problems in acquisition, storage, and analysis of delphinid echolocation signals are described and illustrated. It is shown that adequate bandwidth is the prime requisite for validity in measurement. However, idiosyncracies of the detector and recorder may alter the signal and, therefore, its derived characteristics. Uncertainty about the signal leads to ambiguous results in analysis.

Problems in detection, recording, and analysis of animal sonar signals are described. Specific examples from echolocation studies are discussed. The bionics contributions of animal sonar research are examined, and suggestions for future bionically oriented research are proffered.

Target discrimination performance by two dolphins—an Atlantic bottlenose dolphin, Tursiops truncatus, Montagu, and an Amazon river dolphin, Inia geoffrensis—is described. The targets were a series of pressure-release cylinders of equal length which varied in target strength (i.e., varied in diameter) in 1-dB and 0.5-dB increments about a median (reference) value. The dolphin's task was to identify the reference target when paired with any other target, either larger or smaller. Tursiops achieves 85%–95% correct discrimination with a 1-dB target-strength difference; performance drops to chance at 0.5-dB difference. Inia's, performance is somewhat poorer. The relationship between discrimination performance and echolocation signal characteristics is discussed. [This work was performed under contract with NURDC, San Diego, California.]

A new technique for recording dolphin echolocation signals during target-discrimination tests is described. The technique utilizes sensors attached to the animal. A brief description of the sensors is provided. A short color film of dolphin echolocation tests performed using the attached sensors is shown. Problems in recording the transient-like dolphin echolocation signals are discussed. A short summary of analyses of echolocation signals of two dolphins—an Atlantic bottlenose dolphin, Tursiops truncatus, Montagu, and an Amazon river dolphin, Inia geoffrensis—is presented. [This work was performed under contract with NURDC, San Diego, California.]