| Researchers at the University of Southampton say dolphins appear to use a system that takes advantage of nonlinear math to process echo location signals when they're scattered by bubbles surrounding the marine mammals' prey. The discovery may lead to much more effective sonar technology development. |
series and saw dolphins blowing multiple tiny bubbles around prey as they hunted.The discovery may lead to much more effective sonar technology development.
"I immediately got hooked, because I knew that no man-made sonar would be able to operate in such bubble water," explained Leighton, a professor of ultrasonics and underwater acoustics at the University of Southampton, where he is also an associate dean.
"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," he added. Leighton and colleagues.
In Leighton's research, a more general form of nonlinear mathematical processing is applied to pulses based on models of dolphin echolocation clicks. This biased pulse summation sonar (BiaPSS) reduces 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), rather than relying on the formation of inverted pulses that are used by other methods.
BiaPSS is shown by tank experiments to be effective in distinguishing targets from the clutter generated by bubbles in the ‘field of view’ of the sonar. While this does not prove that dolphins are capable of undertaking such nonlinear mathematical processing, it establishes the fact that such processing makes these dolphin pulses effective in bubbly water for distinguishing between targets and clutter, which is not achieved by the standard sonar processing.
Dolphin math skills have been studied before. Research at the Dolphin Research Center in Florida has already determined that dolphins grasp various numerical concepts, such as recognizing and representing numerical values on an ordinal scale. Marine biologist Laela Sayigh of the Woods Hole Oceanographic Institution said, "In the wild, it would be very useful (for dolphins) to keep track of which areas were richer food sources."
Paul White and student Gim Hwa Chua set out to determine what the amazing ability might be. They started by modeling the types of echo location pulses that dolphins emit. The researchers processed them using nonlinear mathematics instead of the standard way of processing sonar returns. The technique worked, and could explain how dolphins achieve hunting success with bubbles. The math involved is complex. Essentially it relies upon sending out pulses that vary in amplitude. The first may have a value of 1, while the second is one-third that amplitude.
"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."
"Bubbles cause false alarms because they scatter strongly, and a dolphin cannot afford to waste its energy chasing false alarms while the real fish escape," Leighton explained. The engineering specification of dolphin sonar is not superior to the best man-made sonar. A logical deduction from this is that, in blowing bubble nets, either dolphins are ‘blinding’ their echolocation sense when hunting or they have a facility absent in man-made sonar. Here we use nonlinear mathematical functions to process the echoes of dolphin-like pulses from targets immersed in bubble clouds.
The second stage then involves subtracting the echoes from one another, ensuring that the echo of the second pulse is first multiplied by three. The process, in short, therefore first entails making the fish visible to sonar by addition. The fish is then made invisible by subtraction to confirm that it is a true target.
In order to confirm that dolphins use such nonlinear mathematical processing, some questions must still be answered. For example, for this technique to work, dolphins would have to use a frequency when they enter bubbly water that is sufficiently low, permitting them to hear frequencies that are twice as high in pitch.
"Until measurements are taken of wild dolphin sonar as they hunt in bubbly water, these questions will remain unanswered," Leighton said. "What we have shown is that it is not impossible to distinguish targets in bubbly water using the same sort of pulses that dolphins use."
If replicated, the sonar model may prove to be a huge benefit to humans. It might be used in devices able to detect covert circuitry, such as bugging devices hidden in walls, stones or foliage. It could also dramatically improve detection of sea mines. "Currently, the Navy uses dolphins or divers feeling with their hands in such difficult conditions as near-shore bubbly water, for example in the Gulf," he said.
Moreover, the study reveals that there is still much to be discovered about the intelligence of dolphins and other creatures.
SOURCE NBC News
Dolphin math skills have been studied before. Research at the Dolphin Research Center in Florida has already determined that dolphins grasp various numerical concepts, such as recognizing and representing numerical values on an ordinal scale. Marine biologist Laela Sayigh of the Woods Hole Oceanographic Institution said, "In the wild, it would be very useful (for dolphins) to keep track of which areas were richer food sources."
Paul White and student Gim Hwa Chua set out to determine what the amazing ability might be. They started by modeling the types of echo location pulses that dolphins emit. The researchers processed them using nonlinear mathematics instead of the standard way of processing sonar returns. The technique worked, and could explain how dolphins achieve hunting success with bubbles. The math involved is complex. Essentially it relies upon sending out pulses that vary in amplitude. The first may have a value of 1, while the second is one-third that amplitude.
"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."
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| Dolphins herd sardines using 'bubble nets' - Image Source BBC. |
The second stage then involves subtracting the echoes from one another, ensuring that the echo of the second pulse is first multiplied by three. The process, in short, therefore first entails making the fish visible to sonar by addition. The fish is then made invisible by subtraction to confirm that it is a true target.
In order to confirm that dolphins use such nonlinear mathematical processing, some questions must still be answered. For example, for this technique to work, dolphins would have to use a frequency when they enter bubbly water that is sufficiently low, permitting them to hear frequencies that are twice as high in pitch.
"Until measurements are taken of wild dolphin sonar as they hunt in bubbly water, these questions will remain unanswered," Leighton said. "What we have shown is that it is not impossible to distinguish targets in bubbly water using the same sort of pulses that dolphins use."
If replicated, the sonar model may prove to be a huge benefit to humans. It might be used in devices able to detect covert circuitry, such as bugging devices hidden in walls, stones or foliage. It could also dramatically improve detection of sea mines. "Currently, the Navy uses dolphins or divers feeling with their hands in such difficult conditions as near-shore bubbly water, for example in the Gulf," he said.
Moreover, the study reveals that there is still much to be discovered about the intelligence of dolphins and other creatures.
SOURCE NBC News
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