Dolphins produce whistles, clicks, and sounds that resemble moans, trills, grunts and squeaks. They primarily use lower frequency vocalizations for communication and higher-frequency sounds in echolocation, to seek out food and other objects.
Bottlenose dolphins can create noises ranging from 0.25 to 150 Hertz. They rely heavily on sound projection and reception to navigate in dark waters. They can click and whistle simultaneously, and can even create a signature whistle to identify themselves. Mother dolphins may whistle to their calves for several days after birth, creating an acoustic imprint which allows the calf to identify its mother by her whistle.