“What were the sounds of Stonehenge” must be one of the few questions I’ve never heard asked about this iconic monument. After 5,000 years, and innumerable studies and theories as to its origin and use, we still don’t know very much about it. We certainly didn’t know anything about the sounds of Stonehenge. I was born less than forty miles from the monument, have visited it many times, and have read about it extensively but it seems that each time I do there is a new theory about it.
Through the doors of a University of Salford building in Manchester, down a concrete hallway, and inside a foam-covered room, stands a knee-high replica of Stonehenge. These miniature standing stones may give us an augmented understanding of the site. The scale model is at the center of ongoing research into Stonehenge’s acoustical properties, and what its sound might tell us about its purpose.
“We know that the acoustics of places influence how you use them, so understanding the sound of a prehistoric site is an important part of the archaeology,” said Trevor Cox, professor and acoustics researcher at the University.
“We’re gradually finding out more and more about it, but some things we just don’t think we’ll ever be able to find out. We have no way of understanding why people started to build it, and the reason that they continued to work on it may well have changed over the hundreds of years it took to complete,” said Susan Martindale, volunteer manager for English Heritage, the charitable trust that manages Stonehenge.
Thanks to Cox’s recent studies, however, we now know a new and fascinating detail about one of the world’s most enigmatic sites: It once acted as a giant echo chamber, amplifying sounds made inside the circle to those standing within, but shielding noise from those standing outside. This finding has led some to ponder whether the monument was actually constructed as a ritual site for a small and elite group but, again, this is pure speculation.
While conducting a study of “the sonic wonders of the world” 10 years ago, Cox began to wonder whether studying the acoustical properties of Stonehenge might help uncover some of its secrets. “I realized there was a technique in acoustics that had never been applied to prehistoric sites before, and that was acoustic scale modelling,” he said.
Cox set out to create a 1:12 scale replica that he could test inside the university’s semi-anechoic chamber, a room that absorbs virtually all sound, thanks to the geometric foam covering every surface except the floor. To create the replica, Cox first received a computer model from English Heritage, allowing him to better understand what Stonehenge looked like at its fullest configuration, which was about 4,000 years ago.
The model allowed him to create 157 stones, using 3D printing and molding techniques. It took about six months to complete. Once the stones were painted grey, and arranged in the correct distribution according to the computer model, the challenges of the testing process began.
“Everything is a twelfth of the size of the real structure, and that means we have to test at 12 times the frequency,” he said. “You have to get all the loudspeakers and microphones that work at those frequency ranges, and they’re not commonly available.” I don’t understand that but I’m not an acoustics expert!
The results surprised Cox. Although Stonehenge has no roof or floor, sound bounces between the gaps in the stones and lingers within the space. In acoustics, lingering sound is known as reverberation. In addition, Cox’s research found that the stones themselves have an effect on the directionality of voice. In an open, natural environment, like the grassy hill Stonehenge is built on, a speaker facing away from a listener would only be understood about one-third of the time. However, the reflections from the stones at Stonehenge would have amplified the speaker’s voice by four decibels, and that would have increased the number of sentences that could be understood to 100%. These results showed that Stonehenge would have allowed people inside the circle to hear each other quite well, while those outside would have been excluded from any ceremonies taking place.
Cox acknowledges that unanswered questions about the real Stonehenge make it difficult for him to draw definitive conclusions from his work with the scale model. Instead, he sees the acoustics research as another tool to find more clues and build a clearer picture of the site’s qualities. “If we think about human ceremonies, they usually involve some form of sound, whether that’s music or speaking or chanting. And we now know that if they really wanted to be heard, speakers and listeners would have had to have been inside the circle,” he said.
Cox thinks that his discoveries create an even more fascinating mystique for the amazing ability of our ancestors to build the most astonishing monuments, like Stonehenge.
I couldn’t agree more. How on earth could you predict that fifty-ton stones would do that? I suppose that trial and error might give you the answer, but how do you play trial and error with fifty-ton stones. This research gives us a fascinating new insight into Stonehenge – the sounds of Stonehenge – but, as usual with new discoveries at Stonehenge, it opens up a huge raft of questions we never knew to ask before, just adding to the wealth of knowledge we don’t have.
