Echolocation transmitting beam of the Atlantic bottlenose dolphin.

The transmitting beam patterns of echolocation signals emitted by an Atlantic bottlenose dolphin Tursiops truncatus were measured in the vertical and horizontal planes with an array of seven hydrophones. Particular emphasis was placed on accurately verifying the animal's position on a bite-plate/tail-rest stationing device using underwater video monitoring equipment. The major axis of the vertical beam was directed at an angle of 5 degrees above the plane defined by the animal's lips. This angle was 15 degrees lower than previously measured. The vertical beam measurements indicate that the major axis of the transmitting beam is aligned with the major axis of the receiving beam. The horizontal beam was directed forward. The directivity index of 26.5 dB calculated from the beam pattern measured in both planes agreed well with previous calculation of 25.4 dB.