Dolphins communicate vocally through a series of high-pitched clicks and whistles. Dolphins are also thought to employ body language, physical communication and a process known as echolocation in order to communicate with each other.
Dolphins lack the vocal chords and larynx that humans utilize to produce vocal sounds and instead vocalize by moving air within the nasal passage. Dolphins produce whistles and other sounds that resemble grunts, moans and even creaking doors. They produce sounds that vary in volume and frequency even at considerable depths. Dolphins have been observed emitting air from their blowholes during some vocalizations as part of a visual display that may play a role in their communication with one another.
Dolphins also employ a process known as echolocation where high-frequency sound waves are projected. After this projection, the dolphins listen for echoes that reflect off their surroundings. Pods of dolphins also rely on body language in order to communicate vital information such as the location of prey and predators or to establish their positions within the group's social structure. Echolocation and sound production are used in order to perceive the body language and signals of other dolphins in environments and circumstances where sight may be limited.