The sounds vary in volume, wavelength, frequency, and pattern. Social signals have their most energy at frequencies less than 40 kHz. Bottlenose dolphins identify themselves with a signature whistle. A mother dolphin may whistle to her calf almost continuously for several days after giving birth. Odontocetes echolocate by producing clicking sounds and then receiving and interpreting the resulting echo.
Dolphins produce directional clicks in trains.
These sound waves bounce off objects in the water and return to the dolphin in the form of an echo. High frequency sounds don't travel far in water. Because of their longer wavelength and greater energy, low frequency sounds travel farther. The major areas of sound reception are the fat-filled cavities of the lower jaw bones. Sounds are received and conducted through the lower jaw to the middle ear, inner ear, and then to hearing centers in the brain via the auditory nerve.