 In general, three different types of sounds are produced by dolphins (and other toothed whales).These are click trains, which are made of numerous individual clicks, usually broadband signals that change from low value to high value quickly, burst pulses, which are individual clicks with high repetition and can be heard by humans only as a buzzing sound, and whistles, which are signals that are pure-tones and whose frequency varies depending on the time.Dusky dolphins produce all three sounds, but most commonly make burst pulses.