Underwater Acoustic Signatures of Recreational Swimmers, Divers, Surfers and Kayakers
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Non-motorised, recreational water activities were recorded underwater in the controlled setting of a public swimming pool during the off-season. Individuals, one at a time, swam freestyle and breaststroke, snorkelled, scuba-dived, kicked a boogie board and a surfboard, kayaked, and simply jumped into the water. Underwater video and still images were recorded at the same time to interpret the sounds recorded. Most of the sound was due to bubbles generated underwater. Activities involving fins (flippers) were the loudest (boogie boarding and snorkelling), followed by freestyle swimming, surfboard paddling, and kayaking. Breaststroke generated the fewest bubbles and was the quietest. All activities produced bubbles, hence noise, at a characteristic temporal pattern. Scuba-diving exhibited two distinct noise spectra related to inhalation and exhalation. Received levels ranged from 110 to 131 dB re 1 \(\upmu \)Pa (10–16,000 Hz) for all of the activities at the closest point of approach (1 m). The results might have applicability to the monitoring of pools for security reasons, to performance assessments of swimmers, and to studies of the distances at which humans may be detectible by marine animals in the sea.
KeywordsSound signature Swimming performance Kayaking Diving Man-made sound Underwater sound
Thank you to Rebecca Wellard, Leila Fouda, Sylvia Osterrieder, Sven Gastauer, and Nicholas Riddoch, all of the Centre for Marine Science & Technology, for swimming in a cold public pool during the off-season. David Minchin and Malcolm Perry kindly assisted with equipment preparation, calibration, and data collection. The authors are also grateful to Scotch College and the University of Western Australia for the use of their pools during tests, and to Mullaloo Surf Lifesavers through BeachLAB and Ocean Reef SeaRescue for measurements conducted off Western Australia’s beaches.
Funding This study was funded by the Western Australian Government, Office of Science, under the Applied Research Program—Round 2. The Western Australian Government does not endorse any information, product, process or outcome, arising from or in relation to this study.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
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