Little is known about underwater sounds produced by PWCs and their potential impact on marine life. Underwater recordings of PWCs in Bramble Bay, Queensland, Australia, contained broadband energy between 100 Hz and 1kHz and tonal signals associated with impeller blade rotation. The broadband signals were associated with the vibrating bubble cloud that is generated by the high-power jet stream of the vehicle; the frequencies of the tonal signals varied depending on the speed of the PWC. Tonal energy persisted over longer ranges than the noise from the vibrating bubble cloud.In a study in Sarasota Bay, Florida, sounds of PWCs traveling at 25mph or 40mph were recorded and then played to Florida manatees for the purpose of studying their behavioral response. The four underwater PWC recordings were played back at 157-166 underwater dB at 10 m (peak sound level), which were similar to the recorded levels at the same distance. The study found that the frequency of animals directly moving to deeper waters increased during PWC approaches.
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- Miksis-Olds, J., P. L. Donaghay, J.H. Miller, P. L. Tyack, and J.E. Reynolds, III. 2007, "Simulated vessel approaches elicit differential responses from manatees." Marine Mammal Science. 23(3): 629-649.