Design and benchmark tests of a hydrophone array system for whale echolocation recordings

• Published in: Open Journal of Acoustics
• Main Authors: Starkhammar, Josefin, Amundin, Mats, Nilsson, Johan, Jansson, Tomas, Almqvist, Monica, Persson, Hans W
• Format: Article in Journal/Newspaper
• Language: English
• Published: Scientific Research Publishing (SCIRP) 2012
• Subjects: Other Electrical Engineering; Electronic Engineering; Information Engineering; Beluga; Beluga whale; Beluga*; Delphinapterus leucas; toothed whales
• Online Access: https://lup.lub.lu.se/record/96d06d3f-fc38-4d82-b8db-b2aa0e1c278f; https://doi.org/10.4236/oja.2012.23014

This paper describes in depth the design and application considerations of a computer based measurement system enabling 1 MS/s simultaneous sampling of 47 hydrophones for cross sectional recordings of echolocation beams of toothed whales (Odontocetes). An earlier prototype version of the system has previously only been presented as a brief proof of principle that did not offer a complete description of the software and hardware solution. Crucial hardware and software design considerations of the further developed system include the re-arm times of the burst mode sampling and the dual-core distributed execution of the software components. The rearm time was measured to 283 µs, using a 550 µs long sample window around each click. This enables burst mode sampling of clicks with an inter-click interval as short as 833 µs. It is shown through both synthetic benchmark tests of the system and through field measurements of bottlenose dolphins (Tursiops truncatus) and a beluga whale (Delphinapterus leucas) that it is capable of acquiring, analyzing and visualizing data in run-time. It operates effectively also in highly reverberant surroundings like concrete pools and shallow waters. Burst mode sampling allows the system to block reflections with 0.3 - 0.5 m longer propagation paths than the direct path. It is suggested that the system’s compliance to reverberant recording sites makes it valuable in future dolphin echolocation studies.