Dolphins' Use of Nonlinear Mathematics Could Help Improve Manmade Sonar
Dolphins are clever creatures and one of their hunting techniques could help manmade sonar detect targets, such as sea mines, in bubbly water.
When dolphins hunt prey, they blow 'bubble nets' around schools of fish to corral the cluster and make them easier to hunt. Such frothy water would confuse human-made sonar because the bubbles create a sort of white noise in the sonar image, obscuring the target.
Tim Leighton of the University of Southampton's Institute of Sound and Vibration Research (ISVR) and colleagues looked into ways that dolphins might process their own sonar signals to distinguish between the clutter of their own bubble nets and the prey they're after.
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"These dolphins were either 'blinding' their most spectacular sensory apparatus when hunting - which would be odd, though they still have sight to reply on - or they have a sonar that can do what human sonar cannot. ... Perhaps they have something amazing," Leighton said, according to MSNBC.
That amazing skill could be ability to do complex mathematics. In the study, published in Proceedings of the Royal Society A, Leighton along with Paul White and student Gim Hwa Chua used echolocation pulses of a type that dolphins emit, but processed them using nonlinear mathematics instead of the standard way of processing sonar returns.
This reduced the effect of clutter by relying on the variation in click amplitude, such as that which occurs when a dolphin emits a sequence of clicks. Dolphins send out pulses of sonar in different amplitudes, which could answer how they can 'see' through the bubble cloud they create when hunting.
"So, provided the dolphin remembers what the ratios of the two pulses were, and can multiply the second echo by that and add the echoes together, it can make the fish 'visible' to its sonar," Leighton told Discovery News. "This is detection enhancement."
It doesn't end there. Bubbles scattering can trick a dolphin's sonar into thinking it's a fish escaping. So to ensure that their target is truly where they think it is, dolphins would have to subtract the echoes of their sonar from one another, keeping track again of the ratios.
If the first pulse of sonar has a value of, say, 3 and the second pulse has a value of 1, then dolphin would confirm that the echo of the second pulse is three times smaller than the first.
"Although this does not conclusively prove that dolphins do use such nonlinear processing, it demonstrates that humans can detect and classify targets in bubbly water using dolphin-like sonar pulses, raising intriguing possibilities for dolphin sonar when they make bubble nets," Leighton said.
If replicated, the sonar model may prove to be a huge benefit to humans, reports MSNBC. It might be able to detect covert circuitry, such as bugging devices hidden in walls, stones or foliage. It could also dramatically improve detection of sea mines.
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