Design and Benchmark Tests of a Multi-Channel Hydrophone Array System for Dolphin Echolocation Recordings
- 1 Department of Measurement Technology and Industrial Electrical Engineering, Lund University, Lund, Sweden
- 2 Department of Measurement Technology and Industrial Electrical Engineering, Lund University, Lund, Sweden
- 3 Department of Measurement Technology and Industrial Electrical Engineering, Lund University, Lund, Sweden
- 4 Department of Measurement Technology and Industrial Electrical Engineering, Lund University, Lund, Sweden
- 5 Department of Measurement Technology and Industrial Electrical Engineering, Lund University, Lund, Sweden
- 6 Department of Measurement Technology and Industrial Electrical Engineering, Lund University, Lund, Sweden
Abstract
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.
- P. J. Miller and P. L. Tyack, “A Small Towed Beamforming Array to Identify Vocalizing Resident Killer Whales (Orcinus orca) Concurrent with Focal Behavioral Observations,” Deep-Sea Research Part II, Vol. 45, No. 7, 1998, pp. 1389-1405. doi:10.1016/S0967-0645(98)00028-9
- J. Starkhammar, M. Amundin, H. Olsén, M. Ahlmqvist, K. Lindstrom and H. W. Persson, “Acoustic Touch Screen for Dolphins First application of ELVIS—an Echo-Location Visualization and Interface System,” Proceedings of the Institute of Acoustics, Vol. 29, Loughborough University, Loughborough, 2007, pp. 55-60.
- M. Amundin, J. Starkhammar, M. Evander, M. Almqvist, K. Lindstrom and H. W. Persson, “An Echolocation Visualization and Interface System for Dolphin Research,” Journal of the Acoustical Society of America, Vol. 123, No. 2, 2008, pp. 1188-1194. doi:10.1121/1.2828213
- P. W. Moore, L. A. Dankiewicz and D. S. Houser, “Beamwidth Control and Angular Target Detection in an Echolocating Bottlenose Dolphin (Tursiops truncatus),” Journal of the Acoustical Society of America, Vol. 124, No. 5, 2008, pp. 3324-3332. doi:10.1121/1.2980453
- M. Johnson and P. Tyack, “A Digital Acoustic Recording Tag for Measuring the Response of Wild Marine Mammals to Sound,” IEEE Journal of Oceanic Engineering, Vol. 28, No. 1, 2003, pp. 3-12. doi:10.1109/JOE.2002.808212
- J. Starkhammar, M. Amundin, J. Nilsson, T. Jansson, S. Kuczaj, M. Almqvist and H. W. Persson, “47-Channel Burst Mode Recording Hydrophone System Enabling Measurements of the Dynamic Echolocation Behavior of Free-Swimming Dolphins,” Journal of the Acoustical Society of America, Vol. 126, No. 3, 2009, pp. 959-962. doi:10.1121/1.3184536
- W. W. L. Au, “The Sonar of Dolphins,” Springer, New York, 1993. doi:10.1007/978-1-4612-4356-4
- W. W. L. Au, “Echolocation Signals of the Atlantic Bottlenose Dolphin (Tursiops truncatus) in Open Waters,” In: R. G. Busnel and J. F. Fish, Eds., Animals Sonar Systems, Plenum Press, New York, 1980, pp. 251-282.
- M. Fahner, J. Tomas, K. Ramirez and J. Boehm, “Acoustic Properties of Echolocation Signals by Captive Pacific White-Sided Dolphins (Lagenorhynchus obliquidens),” In: J. A. Thomas, C. F. Moss and M. Vater, Eds., Echolocation in Bats and Dolphins, University of Chicago Press, Chicago, 2004, pp. 53-59.
- M. O. Lammers, W. W. L. Au, R. Aubauer and P. E. Nachtigall, “A Comparative Analysis of the Pulsed Emissions of Free-Ranging Hawaiian Spinner Dolphins (Stenella longirostris),” In: J. A. Thomas, C. F. Moss and M. Vater, Eds., Echolocation in Bats and Dolphins, University of Chicago Press, Chicago, 2004, pp. 414-419.