Δευτέρα, 17 Ιουνίου 2013

Are Dolphins Math Geniuses? (Εarth in Transition 18.VII.2012)

dolphin-sonar-bubble-rings-071812You have to be a math genius even just to understand the math skills that dolphins  deploy when they're out on a fishing expedition. The basic idea is that after blowing clouds of bubbles around fish, dolphins have to be able to navigate through those clouds in an environment that simple sonar doesn't operate well in. So the dolphins have to be doing something more sophisticated than any human has ever done with sonar.
Mathematician Tim Leighton and his colleagues think they've figured out the wildly complicated computations that dolphin sonar requires. According to Discovery News:
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 1/3 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."
We already know that bottlenose dolphins have enormous brain power. What we haven't known is very much about why they have such brain power and what they use it for. But studies like these are beginning to give us some insights.
Leighton, a professor of ultrasonics and underwater acoustics at the University of Southampton, said it was when he was watching an episode of the BBC/Discovery TV series "Blue Planet" and saw dolphins blowing multiple tiny bubbles around prey as they hunted that he got intrigued.
"I immediately got hooked, because I knew that no man-made sonar would be able to operate in such bubble water."
Leighton and his team studied the echolocations of bottlenose dolphins in the wild, and have published their conclusions in the prestigious math and physics journal, Proceedings of the Royal Society A. They write:
Dolphins have been observed to blow bubble nets when hunting prey. Such bubble nets would confound the best man-made sonar because the strong scattering by the bubbles generates ‘clutter’ in the sonar image, which cannot be distinguished from the true target.
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.
Dolphins emit sequences of clicks, and, within such a sequence, the amplitude of the clicks varies. Here such variation in amplitude between clicks is exploited to enhance sonar performance.
While standard sonar processing is not able to distinguish the targets from the bubble clutter, this nonlinear processing can. 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.
- See more at: http://www.earthintransition.org/2012/07/are-dolphins-math-geniuses/#sthash.izYmXo12.dpuf

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