Sperm whales ͑Physeter macrocephalus͒ produce multipulsed clicks with their hypertrophied nasal complex. The currently accepted view of the sound generation process is based on the click structure measured directly in front of, or behind, the whale where regular interpulse intervals ͑IPIs͒ are found between successive pulses in the click. Most sperm whales, however, are recorded with the whale in an unknown orientation with respect to the hydrophone where the multipulse structure and the IPI do not conform to a regular pulse pattern. By combining far-field recordings of usual clicks with acoustic and orientation information measured by a tag on the clicking whale, we analyzed clicks from known aspects to the whale. We show that a geometric model based on the bent horn theory for sound production can explain the varying off-axis multipulse structure. Some of the sound energy that is reflected off the frontal sac radiates directly into the water creating an intermediate pulse p1/2 seen in off-axis recordings. The powerful p1 sonar pulse exits the front of the junk as predicted by the bent-horn model, showing that the junk of the sperm whale nasal complex is both anatomically and functionally homologous to the melon of smaller toothed whales.
Passive acoustic tracking of sperm whales was conducted during three cruises (2001, 2002, and 2003) in the northwestern part of the Mediterranean Sea using a 128‐element towed linear array with real‐time beamforming capabilities. This allowed angular separation of sperm whales clicking from different horizontal directions, as well as an enhanced signal‐to‐noise ratio. Thus, when several diving animals were present, the description of individual click series was possible. Over a total of 279 complete dives, sperm whales were recorded clicking an average of 35 min per dive. The acoustic repertoire heard from diving sperm whales consisted of usual clicks, creaks, codas, and ttumpets. Trumpets occurred at the beginning of 45 dives. One hundred and thirty‐one codas, 98% belonging to the Mediterranean pattern 3+1, were recorded, usually at the end of the dive.
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