Directional properties of bottlenose dolphin (Tursiops truncatus) clicks, burst-pulse, and whistle sounds

The directional properties of bottlenose dolphin clicks, burst-pulse, and whistle signals were measured using a five element array, at horizontal angles of 0 degrees, 45 degrees, 90 degrees, 135 degrees, and 180 degrees relative to a dolphin stationed on an underwater biteplate. Clicks and burst-pulse signals were highly directional with directivity indices of similar to 11 dB for both signal types. Higher frequencies and higher amplitudes dominated the forward, on-axis sound field. A similar result was found with whistles, where higher frequency harmonics had greater directivity indices than lower frequency harmonics. The results suggest the directional properties of these signals not only provide enhanced information to the sound producer (as in echolocation) but can provide valuable information to conspecific listeners during group coordination and socialization. (C) 2012 Acoustical Society of America. [DOI: 10.1121/1.3676694]