Navy Taps Dolphin Brains for Next-Gen Sonar

The key to finding undersea mines may lie in Flipper's brain. The Navy is looking for new ways to search the murky coastal waters for threats. By studying how bottlenose dolphins "interpret the signals they emit and receive in the water," military researchers believe "they can eventually develop a short range, high-resolution sonar" to do the trick, National Defense magazine reports.

*Dolphins, like bats, have a biological sonar system called echolocation. They produce ultrasonic sounds that reflect off objects to “see” the environment around them... *

*Dolphins emit short echolocation clicks on the order of 100 microseconds in beam patterns that shift in frequencies, source levels and bandwidth. Those impulse signals range from 35 to 135 kilohertz in frequency and 80 to
100 kilohertz of bandwidth. *

Dolphins are able to
“tune” their sonar for various tasks. For example, in waters where snapping shrimp generate background noise — like sizzling bacon, to human ears — dolphins echolocate at higher frequencies that are optimal against the din...

Scientists want to build sonars that can do the same thing. It’s called environmentally adaptive sonar.

It's one of an array of abilities that the military would like to learn from undersea critters. The Army is looking to create synthetic gills. Darpa researchers have built prosthetic fins for military divers. Other agency scientists are trying to get those divers to act like sea lions, and "redirect oxygen demand" on command.

Pentagon-funded studies are peering inside sharks' heads, to examine the jelly-filled canals called "the ampullae of Lorenzini." The predators use 'em to detect the itty-bitty electrical charges a fish makes when it flexes its muscles, or swims counter to the earth's natural magnetic fields. It's a real-live sixth sense -- one the military would like to have for itself.

The Navy Marine Mammal Program's effort to harness dolphin's sixth sense is called "Biosonar." It has two main components.

1) the development of a biosonar measurement tool (BMT) and 2) the design, fabrication and testing of a prototype dolphin-based sonar
(DBS) as a test platform to evaluate various biomimetic signal-processing strategies gleaned from the BMT...

• The BMT is a dolphin-wearable computer that collects the emitted clicks of the animal and all the returning echoes during a free open-ocean target search and detection task. The BMT has an on-board 9-degree of freedom inertial navigation system that collects the animal's position and movement in three dimensions and is earth-referenced using a differential GPS. The enormous amounts of data collected by this device are reconstructed in a virtual environment in order for researchers to explore and focus on a section of the animal's total behavior and signals that can guide development of underlying principals of the animal's search and detection strategies.*

*National Defense *magazine says that Navy researchers have a theory that the dolphins actually have "two hearing systems."

One is devoted to communication sounds — the whistles and other noises they make in social settings. The scientists believe the other one is a passive system that has special timing considerations in a portion of the brain that becomes engaged when they begin to echolocate. When dolphins generate a click, they somehow know when the echo will return, and they can ignore other incoming signals until they receive the echo.

*The scientists plan to experiment with the dolphins by using controlled electronic targets. They will place earphones on the jaw and the dolphin’s forehead. When the dolphin produces a click, the scientists can manipulate the sound and present it back to the animal when they believe it would return from a target. By conducting the brain images, the scientists will begin finding clues into the dolphin’s signal processing abilities. *

(Photo: National Defense)

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