Dolphin vocalisation analysis using an ADSP 21020

Underwater the only effective means of transmitting signals is acoustically. This century man has exploited this principle and developed a wide range of sonar systems for tasks such as underwater communication, sea bottom profiling and target detection. However, these systems when compared to the sonar systems of dolphins are rudimentary. The primary sensory system of a dolphin is acoustic and can be likened to the function of the human eye, in that a dolphin will use an acoustic signal to visualise its environment. The exact nature and purpose of most of the acoustic vocalisations of dolphins are poorly understood. It is known that dolphins can distinguish between objects of different shape, density and wall thickness using echolocation clicks. However, little is known about their wide repertoire of other acoustical signals. In this paper a DSP system that allows a real time analysis of the frequency composition of dolphin vocalisations is presented. The system, designed and built around ADSP 21020, digitises dolphin vocalisations at a rate of 44100 Hz, generates a N-point FFT and displays the results as a rolling spectrogram. Using this system enhanced interpretation and greater insight into the structure of cetacean vocalisations has been possible and has enabled the identification of what is thought by the authors to be new dolphin vocalisation. This vocalisation is of the correct time duration and frequency composition to suggest that it is a Doppler sensitive pulse used by dolphins to track and follow their prey