Prehistoric cave paintings, canyon art and structures such as Stonehenge may have been inspired by spooky noises believed to be from the spirit world, a scientist has claimed.
Sound waves reflecting off a cliff face or cave wall can produce echoes that give the impression of a voice calling from within the rock, said US expert Dr Steven Waller.
Echoes of clapping could also sound similar to hoof beats or a herd of stampeding animals.
"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 Dr 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."
Stonehenge and other megalithic sites may be linked to the haunting effects of sound patterns, said Dr Waller, who spoke at the Acoustical Society of America's annual meeting in Indianapolis.
He believes this may have influenced the positioning of the Stonehenge rock slabs.
"Sound can easily lead to auditory illusions of the supernatural," he said. "This leads to the question: what other illusions are we living under due to other phenomena that we are currently misinterpreting?"