The vocalizations emitted by toothed whales and dolphins (odontocetes) are all produced underwater. Odontocetes produce a wide variety of sounds which include clicks, whistles, and pulsed sounds. These sounds were once thought to be produced in association with a vibrating larynx, but studies with live dolphins showed that the vocal folds did not move during high frequency vocalizations. Where is the sound coming from? The answer lies in the nasal system. The nasal system is made up of a number of nasal air sacs and plugs that open and close when air is moved from one sac to another. The details of sound production in toothed whales are complex, and the exact site of sound generation is still a controversial topic. Movement of air stimulates vibrations, which may be amplified by air sacs that act as resonators. The sound is then channeled through fats in the melon to the water in front of the animal. The beam or sound generated by toothed whales is very precise due to the channeling inside the head and melon.

The large forehead of this Beluga whale is called the melon. It helps focus outgoing sound waves. Photo ©Tom Kieckhefer.

The details of sound production in baleen whales (mysticetes) and manatees and dugongs (sirenians) are not well known. Both groups of animals produce vocalizations and possess a larynx and vocal folds. Manatees make high pitched squeaks, while baleen whales produce lower frequency thumps, moans, groans, tones, and pulses.

All the major groups of marine mammals also produce other sounds that are used for acoustic communication. These sounds are typically made by slapping a body part against the surface of the water. This action makes both a sound and splash. Tail or fluke slapping is common in the cetaceans and sirenians. Kerplunks are also made by the tail. Other parts of the body that are typically used in producing noise in a slapping manner are pectoral fins and the body as a whole during lunges and breaches. Jaw claps are made either above or underwater by forcefully clapping together the upper and lower jaws. These types of sound often signal aggression in toothed whales.

Marine mammals make a variety of sounds that may be used for acoustic communication. Bottlenose dolphins make a "bang" sound when they clap their jaw. The sound of humpback whales crashing onto the surface of the water can be heard underwater. Photos ©Tom Kieckhefer.

References
• King, J.E. 1983. Seals of the World, 2nd ed. Comstock Publishing Associates, Ithaca, NY.
• Pabst, D.A., Rommel, S.A. and McLellan, W.A. 1999. The Functional Morphology of Marine Mammals. Pages 15-72 in Reynolds, J.E. III and Rommel, S.A. (eds.). Biology of Marine Mammals. Smithsonian Institution Press, Washington D.C.
• Ridgway, S.H. and Carder, D.A. 1988. Nasal pressure and sound production in an echolocating white whale, Delphinapterus leucas. Pages 53-60 in Nachtigall, P.E. and Moore, P.W.B. (eds.). Animal Sonar: Processes and Performances. Plenum Press, New York, NY.
• Wartzok, D. and Ketten, D.R. 1999. Marine Mammal Sensory Systems. Pages 117-175 in Reynolds, J.E. III and Rommel, S.A. (eds.). Biology of Marine Mammals. Smithsonian Institution Press, Washington D.C.
• Wells, R.S., Boness, D.J. and Rathbun, G.B. 1999. Behavior. Pages 324-422 in Reynolds, J.E. III and Rommel, S.A. (eds.). Biology of Marine Mammals. Smithsonian Institution Press, Washington D.C.

Additional Resources
• Sonar in Dolphins - Neuroanatomy

For more information on how other marine animals produce sounds use the following links:
Marine Mammals	Fish	Invertebrates