Courtesy of Whitlow Au

Dr. Whitlow Au studies sound production and reception by marine animals, concentrating on dolphins. His work has examined the ability of a dolphin to transmit, receive, and process sounds. Dr. Au discovered that a dolphin changes its echolocation clicks depending on how far it is from to its target. A dolphin decreases its click interval (the amount of time between successive clicks) and decreases the amplitude of the clicks as it nears its target. Originally, it was thought that dolphins made clicks less often when they were further away because they were trying to remain hidden. Dr. Au, however, showed that it is a result of the way dolphins process information from their clicks. A dolphin waits until it hears the echo from a click before making another click. Therefore, as a dolphin approaches its target, the distance between the animal and the target decreases, allowing the dolphin to decrease its click interval. As this is occurring, the dolphin also decreases the amplitude of its clicks. Dr. Au has compared dolphin echolocation to bat echolocation and other types of sonar to study similarities and differences between various animals.

Related Links and Resources
• Au, W.W.L. and Benoit-Bird, K.J. 2003. Automatic gain control in the echolocation system of dolphins. Nature 423 (19 June 2003): 861-863.
• Au, W.W.L. 1993. The Sonar of Dolphins. Springer-Verlag: New York. 277 pp.
• Au, W.W.L., Floyd, R.W., Penner, R.H. and Murchison, A.E. 1974. Measurement of echolocation signals of the Atlantic bottlenose dolphin, Tursiops truncatus Montagu, in open waters. Journal of the Acoustical Society of America 54: 1280-1290.