Whitlow W. L. Au
Paul E. Nachtigall
Jeffrey L. Pawloski
Hawaii Inst. of Marine Biology, Univ. of Hawaii, P.O. Box 1106, Kailua, Hawaii 96734
The acoustic thermometry of ocean climate (ATOC) program of Scripps Institute of Oceanography and the Applied Physics Laboratory, University of Washington, will broadcast a low-frequency 75-Hz phase-modulated acoustic signal over ocean basins in order to study ocean temperatures on a global scale. One of the major concerns is the possible effect of the ATOC signal on marine life, especially on dolphins and whales. In order to address this issue, the hearing sensitivity of a false killer whale (Pseudorca crassidens) and a Risso's dolphin (Grampus griseus) to the ATOC sound was measured behaviorally. A staircase procedure with the signal levels being changed in 1-dB steps was used to measure the animals' threshold to the actual ATOC coded signal. The results will be used to examine how the ATOC sound will affect the hearing capability of these small cetaceans. The relative effect of the ATOC sound will also be compared with effects from other sources of noise such as aircraft, ocean going ships, pleasure craft, and other whales.