Many of the bluestones at the prehistoric stone circle in Wiltshire, England make 'distinctive (if muted) sounds' when hit with small hammerstones, say researchers.
Built between 3100 BC and 1100 BC, the monument is made up of bluestone, sarsen and Welsh sandstone – some of the stones reach as high as 30 feet and weigh up to 25 tons.
But the purpose as to why and how the rocks got there remains a mystery.
In a study titled "Stone Age Eyes and Ears: A Visual and Acoustic Pilot Study of Carn Menyn and Environs, Preseli, Wales" published in the cross-disciplinary journal Time and Mind, researchers from the Royal College of Art, London suggest that some of the bluestone rocks at Stonehenge were lugged all the way for hundreds of miles because of their unique acoustic properties.
In many ancient cultures, so-called ringing rocks were believed to contain spirits or have magical properties, Paul Devereux, researcher and an author of the paper told the Monitor. It is possible that the architects of Stonehenge may have held similar beliefs, he says.
The source of origin for many bluestone rocks in Stonehenge have been traced to the Carn Menyn in Preseli Hills, Wales, roughly 160 miles from Stonehenge. A village in the area, Maenclochog, whose name means "bell or ringing stones," used bluestones as church bells until the eighteenth century.
The late British archaeologist and "rock gong" pioneer Bernard Fagg had suspected the presence of ringing or musical rocks on or around Preseli. He also suggested that it was possible that there was a sacred link between these sounds and the Neolithic monuments or landscapes found within the region. The researchers at the Royal College of Art wanted to test how many rocks were actually "ringing rocks" and what kind of sound they produced.
After conducting percussion tests on thousands of bluestones at Carn Menyn, researchers found that a a large number of rocks produced metallic sounds like a bell, gong, or tin drum when struck with hammerstones, Dr. Devereux says.
After obtaining permission from English Heritage, which protects England's historic environment, the scientists started testing the bluestones at Stonehenge.
They found that a handful of them did "make distinctive (if muted) sounds" which is an indication that, had there been enough resonant space, they would be fully "lithophonic." The fact that the bluestones were supported in concerete or were fixed to the ground, did not provide them with enough room to vibrate and produce sounds that were produced by the ones found on Carn Menyn, researchers noted in a Royal College of Art press release.
Moreover, many of them had markings which indicate that they had been struck in the past, according to the paper.
Many theories of Stonehenge have emerged in the past. Earlier studies had suggested that Stonehenge was probably used as a burial site or it might have been an ancient astronomical observatory.