All species of marine mammals are known to make sound. Marine mammals produce sounds that are used for communication, feeding, and navigation. Almost all vocalizations are produced through the movement of air from one area of the head to another. In humans, air is moved from the lungs and across the vocal folds (also known as vocal cords). The vocal folds vibrate which produce sounds that we form into words and other communication signals (vocalizations). Marine mammals such as seals and sea lions can produce vocalizations using the same mechanisms as humans do. Other marine mammals such as dolphins and whales pass air through air sacs in their heads to produce vocalizations. These animals are not thought to produce sounds using their vocal folds. Marine mammals also have the capability to produce and use other sounds for acoustic communication. The animals may intentionally slap their bodies on the water or slap body parts together to make distinct sounds, like the sounds produced by a whale breaching or slapping its flippers.

Dolphins produce sounds by passing air through air sacs in their head. Adapted from Dolphin Acoustical Structure (1991) Scheifele, P.M. NUSC TR3080

Pinnipeds, polar bears, and sea otters produce a variety of vocalizations which include barks, cries, howls, roars, and snorts. It is generally believed that these sounds, which are produced in air, are created by the vibration of vocal folds in the larynx. Air passed from the lungs across the vocal fold ligaments creates sound by vibration. The sound produced by vibration can then be modified by the placement of teeth and tongue, or by the shape of the mouth. The final sound is also influenced by sound passing through resonating chambers such as sinuses and other air sacs found in the head. Some pinnipeds also produce vocalizations underwater, but these sounds are not thought to be associated with vibrating vocal folds. Instead, the sound is generated by cycling air through air pouches in the animal's head. This mechanism is thought to be the generating source for underwater sounds of some seals, seal lions, and male walruses. Underwater vocalizations can include clicks, trills, warbles, whistles, and bell-like sounds.

Male California sea lions, like the one pictured above, bark profusely when defending their territories. In air, these sounds are produced using the same mechanisms that humans use. Photo ©Tom Kieckhefer.