The Biology of Animals . Whales, Dolphins and Porpoises . The Dolphin in History . 8 - 200 kHz Howlett, Rory. New Scientist .
Dolphins also emit pure tone sounds called whistles and chirps.
Each individual has its own unique whistle that serves to distinguish who and where the whistle is coming from. The loudness and the duration of the whistle are also important. It is quite ironic to find so many variations and inconsistencies among these values. The low end ranges from 100 Hz to 8,000 Hz with three sources agreeing on a value of 1,000 Hz. One should seek the standard deviation of the machinery used before stating which is wrong and which is correct.