Dolphins Talk Like Humans

"Peter Madsen, a researcher in the Department of Biological Sciences at Aarhus University, and his team studied how dolphins communicate by digitizing and reanalyzing recordings made in 1977 of a 12-year-old male bottlenose dolphin.
The dolphin breathed in a "heliox" mixture consisting of 80 percent helium and 20 percent oxygen -- a concoction that causes humans to sound like, as the scientists put it, Donald Duck. The reason is because the mixture has a sound speed that's 1.74 times higher than normal air. If a person whistles after sucking in helium, the pitch of the tune will then be 1.74 times higher than if he or she whistles after breathing in just air.

"We found that the dolphin does not change pitch when it is producing sound in heliox, which means that its pitch is not defined by the size of its nasal air cavities, and hence that it is not whistling," Madsen said. "Rather, it makes sound by making connective tissue in the nose vibrate at the frequency it wishes to produce by adjusting the muscular tension and air flow over the tissue."

"That is the same way that we humans make sound with our vocal cords to speak," he added."

via Discovery News/read more