Study Finds Schools of Fish Can Make Less Noise Than a Solitary Swimmer
taylorvich writes:
https://phys.org/news/2024-04-schools-fish-noise-solitary-swimmer.html
New findings by Johns Hopkins University engineers working with a high-tech simulation of schooling mackerel, offer insight into why fish swim in schools and promise for the design and operation of much quieter submarines and autonomous undersea vehicles.
"It's widely known that swimming in groups provides fish with added protection from predators, but we questioned whether it also contributes to reducing their noise," said senior author Rajat Mittal. "Our results suggest that the substantial decrease in their acoustic signature when swimming in groups, compared to solo swimming, may indeed be another factor driving the formation of fish schools."
The work is published in Bioinspiration & Biomimetics.
The team created a 3D model based on the common mackerel to simulate different numbers of fish swimming, changing up their formations, how close they swam to one another, and the degrees to which their movements synched. The model, which applies to many fish species, simulates one to nine mackerel being propelled forward by their tail fins.
The team found that a school of fish moving together in just the right way was stunningly effective at noise reduction: A school of seven fish sounded like a single fish.
"A predator, such as a shark, may perceive it as hearing a lone fish instead of a group," Mittal said. "This could have significant implications for prey fish."
The single biggest key to sound reduction, the team found, was the synchronization of the school's tail flapping-or actually the lack thereof.
If fish moved in unison, flapping their tail fins at the same time, the sound added up and there was no reduction in total sound. But if they alternated tail flaps, the fish canceled out each other's sound, the researchers found.
Journal Reference:
Ji Zhou et al, Effect of schooling on flow generated sounds from carangiform swimmers, Bioinspiration & Biomimetics (2024). DOI: 10.1088/1748-3190/ad3a4e
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