Bullroarer (music)

Bullroarer (music)

The bullroarer, rhombus, or turndun, is an ancient ritual musical instrument and a device historically used for communicating over greatly extended distances. It dates to the Paleolithic period, being found in Ukraine dating from 17,000 BC. Anthropologist Michael Boyd, a Bullroarer expert, documents a number found in Europe, Asia, the Indian sub-continent, Africa, the Americas, and Australia.

In ancient Greece it was a sacred instrument used in the Dionysian Mysteries and is still used in rituals worldwide.

Along with the didgeridoo, it is prominent technology among Australian Aborigines, used in ceremony across the continent.

The bullroarer has sometimes been incorrectly used as a means of seeming to demonstrate the Doppler effect in sound waves. In such cases, an incorrect explanation which might be given is that as the instrument travels around its circular path, its perceived pitch may, to a third party, seem to appear to rise and fall as it moves closer and farther away, respectively. This explanation is credible only because it is hard to keep track of the circling blade's location and at the same time to associate that with the bullroarer's pitch changes. In fact, when the bullroarer is whirled around one's head in a horizontal plane, the pitch rises and falls in its usual manner even though the spinning neither approaches much nor retreats much from the ears of the whirler. There is essentially no Doppler effect involved in that case, only the speeding up and slowing of the axially rotating blade.

The greatest pitch variations are not caused by the approach and recession of the spinning blade at all. Rather, as the blade spins, it winds up or loosens the twisting of the cord that holds the blade. When the twist in one direction gets tight enough, the blade spin will slow and then it will reverse its spin and unwind rapidly, and will continue that direction of spin until the cord twist tightens again. At that time, the blade will reverse its spin direction again. During the reversals the blade's rotational speed about its long axis rises and falls. This variation in its own rapid rate of spin is what produces the pitch variation. There is no necessary link between a bullroarer's pitch and how fast the entire bullroarer is going around on its cord in its large circle, or where the blade is at any given time in relation to a hearer, or whether it is approaching or receding from that listener. In fact, two listeners on opposite sides of the person whirling the bullroarer will hear simultaneous and nearly identical rises and falls of the pitch even though the blade will be approaching one and going away from the other at any given time.