Cross-correlation, triangulation, and curved-wavefront focusing of coral reef sound using a bi-linear hydrophone array

A seven element, bi-linear hydrophone array was deployed over a coral reef in the Papahãnaumokuãkea Marine National Monument, Northwest Hawaiian Islands, in order to investigate the spatial, temporal, and spectral properties of biological sound in an environment free of anthropogenic influences. Loc...

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Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2015-01, Vol.137 (1), p.30-41
Main Authors: Freeman, Simon E, Buckingham, Michael J, Freeman, Lauren A, Lammers, Marc O, D'Spain, Gerald L
Format: Article
Language:English
Subjects:
Acoustics - instrumentation
Algorithms
Animals
Aquatic Organisms - physiology
Coral Reefs
Demography
Equipment Design
Marine Biology - instrumentation
Marine Biology - methods
Pacific Ocean
Signal Processing, Computer-Assisted
Signal-To-Noise Ratio
Sound
Sound Spectrography - instrumentation
Sound Spectrography - methods
Spatial Analysis
Temperature
Transducers
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Summary:A seven element, bi-linear hydrophone array was deployed over a coral reef in the Papahãnaumokuãkea Marine National Monument, Northwest Hawaiian Islands, in order to investigate the spatial, temporal, and spectral properties of biological sound in an environment free of anthropogenic influences. Local biological sound sources, including snapping shrimp and other organisms, produced curved-wavefront acoustic arrivals at the array, allowing source location via focusing to be performed over an area of 1600 m(2). Initially, however, a rough estimate of source location was obtained from triangulation of pair-wise cross-correlations of the sound. Refinements to these initial source locations, and source frequency information, were then obtained using two techniques, conventional and adaptive focusing. It was found that most of the sources were situated on or inside the reef structure itself, rather than over adjacent sandy areas. Snapping-shrimp-like sounds, all with similar spectral characteristics, originated from individual sources predominantly in one area to the east of the array. To the west, the spectral and spatial distributions of the sources were more varied, suggesting the presence of a multitude of heterogeneous biological processes. In addition to the biological sounds, some low-frequency noise due to distant breaking waves was received from end-fire north of the array.
ISSN:0001-4966
1520-8524
DOI:10.1121/1.4904523