Getting a clearer picture of how bats use echolocation
Only a limited number of studies have collected and analysed the echoes generated by prey and vegetation. However, no data existed on the statistics of the echoes generated by complex environments and encountered by bats during flight. Therefore, scientists knew what the echo from a plant looked like, but not how the echo from a row of vegetation changed as the bat flies past it. The CHIROCOPTER (A remote controlled helicopter for investigating the echoes experienced by bat during navigation) project collected a large sample of echoes from the environment as they would be experienced by flying bats. This was done by using an ensonification device comprising an ultrasonic emitter and an array of microphones. The device was used to scan a number of city park environments and over two million pulse echoes were collected. Researchers used the collected data to test their hypothesis that bats match the output of the cochlea of the inner ear to a set of stored templates. Put simply, bats ‘listen’ to how an environment sounds rather than trying to infer how it looks by deriving a 3D layout of objects. By using a template matching approach bats avoid the need for complex reconstruction algorithms that extract 3D information from a 1D signal at each ear. Researchers used a number of mathematical measures to determine the properties of the templates and it was concluded that the templates could support navigation. Furthermore, simulation studies were conducted that demonstrated how bats use the templates to build a map of an environment, such as a forest. Insights gained from CHIROCOPTER will help to create bio-inspired sonar in robots, enabling them to copy the ability of bats to navigate under very demanding circumstances.
Keywords
Bats, echolocation, CHIROCOPTER, ensonification, ultrasonic, cochlea, templates, 3D, algorithm, sonar, robots
