Vocalization of Bottlenose DolphinsHelen Magee, Biology 342 Fall 2007 |
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Mechanism
How Dolphins Can Produce Multiple Sounds at Once
Figure 1: Whistle During Series of Clicks(6)
Figure 2: Two Whistles Within a Series of Clicks (6)
Dolphins are able to do this because they have two separate systems that allow them to emit sounds. When dolphins make the clickimg sounds, it shocks the resonant frequencies and harmonics of cavities in the head of the dolphin, such as variable sacs, fixed sinuses and the fixed nasal passage. The whistle sound is produced from the vibration of these cavities. The clicking sound can also be produced from these cavities, at the same time as the whistle sound(6). The frequencies of both the whistles and the clicks can change, because the cavities change in size and shape.
Producing Sound Out of the Water As well as vocalizing under water, dolphins can also produce sounds in the air. To create the whistle sound outside of water, the dolphin brings its blowhole above the surface of the water, and emits a whistle sound through its blowhole. Unlike when it produces this same sound under water, when the whistle sound is made above water the sound is much quieter and small bubbles are also produced (6). Other sounds that the dolphin makes, including clicks, blats, squawks and quacks, are internally produced sounds that the dolphin releases through its blowhole into the air(6).
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