Real-Time Acquisition of Echolocation Signals by Wild Atlantic Spotted Dolphin, Stenella frontalis, Utilizing Hydrophone Arrays with Simultaneous Underwater Video.

Abstract

Abstract : A technique using multi-element arrays of hydrophones with underwater video recording was developed as a tool to accurately measure echolocation signals of free-swimming dolphins. Two configurations of hydrophones, including a line array of three hydrophones spaced at 30 cm and a symmetrical star configuration of four hydrophones spaced at 45.7 Cm, were used. The arrays were held by a skin diver while dolphins oriented on the arrays. Video and acoustic signals were cabled back to the boat. A real-time analog/digital data acquisition system operating at 500 kHz was used to detect, digitize, and store echolocation signals. Spotted dolphin echolocation signals had bimodal frequency spectra with frequency peaks at 40-60 kHz, and 120-140 kHz. Peak to peak source levels up to 210 dB re 1 uPa were measured. Bandwidth clustered around 40 kHz. This system was productive as a portable field tool for acquiring and measuring, real-time, echolocation signals of free-ranging dolphins.