Since there can be no periodic tensing and relaxing of vocal fold muscles without a connection to the elephant's brain, low-frequency vibrations in the excised larynx clearly demonstrate that the "purring" mechanism is unnecessary to explain infrasounds. Thus, elephants "sing" using the same physical principles as we do, but their immense larynx produces very low notes.
As an additional insight, the scientists were able to get a very clear look at some fascinating types of vibration called "nonlinear phenomena". When a baby cries, or a heavy metal singer screams, the vocal folds vibrate in an irregular manner, which is very grating to our ears. Young elephants also scream and roar, and the mechanism they use is again identical to that seen in humans.
This research shows that the physical principles underlying the human voice extend over a remarkable range, from bat's incredibly high vocalizations (too high for us to hear), all the way down to elephants' subaudible infrasounds. How whales, the largest animals, make their even lower frequency sounds remains to be determined.
|Contact: Dr. Christian Herbst|
University of Vienna