Dolphin vocalization mechanisms.
Although humans have difficulty whistling when in a habitat that is more than 20 meters underwater, dolphins can make certain sounds at great depths through a related mechanism. Other dolphin sounds, such as clicks and complex buzzes, are produced by vibrations of the tissue of the nasal plugs, apparently without the use of the larynx; in these instances, the air sacs act as reservoirs. This was determined from studies of Tursiops truncatus and Delphinus delphis with harmless ultrasonic beams projected noninvasively to determine movements of the air sacs.
Mackay
R S
RS
Liaw
H M
HM