Biometic Sonar Systems

Wouldn’t it be nice to see in the dark? Many animals have evolved strategies to help them do this, but one of the most interesting is to use sound to 'illuminate' their environment.

Dolphins, like bats have evolved a sensory system that uses ultrasound to help them see in conditions of poor visibility. Bats need to navigate and hunt for food at night and in dark caves; while dolphins also need to navigate, keep in contact with their group members and catch prey both at night and in coastal waters in which visibility is often limited by plankton or sediment suspended in the water – a little like fog on land. Dolphin SONAR (Sound Navigation and Ranging) which is sometimes called echolocation, is very sophisticated and we still have a lot to learn about how dolphins are able to perceive very fine resolution details, tell the difference between different materials, different sizes and shapes of objects, and have the ablility to tune their SONAR system to detect objects at widely different ranges.

It might be surprising to learn that humans can also use SONAR both in air and underwater, especially when they are given the right tool to improve their natural ability; and blind people seem especially good at this task. We are studying the ability of human to use SONAR to tell the difference between objects of different shapes, sizes and materials to help us understand which features of an object are important. In this way, we hope to learn more about marine mammal SONAR.

Our research explores the contribution of higher sensory processing in underwater target discrimination and classification using bio-mimetic echolocation signals. By providing human subjects with the ability to use a dolphin-like bio-mimetic SONAR system, the project will explore their ability to detect and classify target objects. Signals with different properties are being explored. These might not only be dolphin-like click trains but perhaps chirps similar to those used by the Harbour porpoise. This approach should enable a comparison of human echolocation underwater with that of dolphins, but perhaps as importantly, our subjects will be able to give verbal feedback about scanning methods, target features and confounding environmental factors such as unwanted sound scattering.