Steven J. Waller, from Rock Art Acoustics, will describe a number of ways virtual sound images and absorbers that could have appeared "supernatural" to the ancestors of humans, which could have possible inspired their creation of mysterious artistic works, at the 168th Meeting of Acoustical Society of America to be held on Oct. 27 through Oct. 31 at the Indianapolis Marriott Downtown Hotel.

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"Ancient mythology explained echoes from the mouths of caves as replies from spirits, so our ancestors may have made cave paintings in response to these echoes and their belief that echo spirits inhabited rocky places such as caves or canyons," explained Waller.

Similar to the way light reflects and offers an illusion of seeing one's self copied in a mirror, sound waves that reflect off a surface are identical mathematically to the sound waves that come from virtual sound sources behind a reflecting plane, such as the face of a large cliff.

"This can result in an auditory illusion of somebody answering you from within the rock," Waller said.

While hoof beats may sound similar to the echoes of clapping hands, several echoes inside a cave can mesh together into a reverberation so thunderous that could possibly mimic the sound of hoofed animals stampeding, Waller pointed out.

"Many ancient cultures attributed thunder in the sky to 'hoofed thunder gods,' so it makes sense that the reverberation within the caves was interpreted as thunder and inspired paintings of those same hoofed thunder gods on cave walls," said Waller. "This theory is supported by acoustic measurements, which show statistically significant correspondence between the rock art sites and locations with the strongest sound reflection."

Ancient cultures may have also misinterpreted other acoustical characteristics as they were unaware of the theory of sound waves. Waller observed a resemblance between Stonehenge and an interference pattern, so he put up such a pattern in an open area with two flutes "droning the same note" to find what would it sound like.

"The quiet regions of destructive sound wave cancellation, in which the high pressure from one flute cancelled the low pressure from the other flute, gave blindfolded subjects the illusion of a giant ring of rocks or 'pillars' casting acoustic shadows," Waller said.

After traveling to England, he demonstrated that the landmark does actually radiate acoustic shadows that resemble the similar pattern of interference.

"My theory that musical interference patterns served as blueprints for megalithic stone circles - many of which are called Pipers' Stones - is supported by ancient legends of two magic pipers who enticed maidens to dance in a circle and turned them all into stones," Waller noted.

TagsSound, Prehistoric art, art, Rock Art Acoustics, Supernatural, Ancient cultures, Ancient people, ancestors, Stonehenge, Stampede