The fascinating new theory about the origin of Stonehenge – 05/06/2023 – Science

Passing through the doors of a university building, crossing a concrete corridor and entering a room covered in foam, we find a miniature replica of one of the most mysterious monuments ever built in the world: Stonehenge.

The replica is not open to the public, but it could give the millions of people who visit the real site each year a better understanding of the imposing stone structure covered with lichens, built some 5,000 years ago.

In fact, this scale model is the center of ongoing research into the acoustic properties of Stonehenge, which is trying to discover what the structure’s sound might tell us about its purpose.

“We know that the acoustics of places influence how they are used. Therefore, understanding the sounds of a prehistoric site is an important part of archaeology”, according to professor and researcher of acoustics Trevor Cox, from the University of Salford in Manchester, UK.

Stonehenge is the best-known and most architecturally sophisticated stone circle in the ancient world. But archaeologists still don’t know who built it, or what it was used for.

There are theories that suggest it was used as a burial ground, a place of healing or even a celestial calendar, as the spaces in the outer stone ring are in perfect alignment with the summer and winter solstice.

But as time goes by, the huge monument built on a grassy hill in the Wiltshire countryside of southwest England remains a mystery.

“We’re gradually discovering more and more about it, but there are some things we don’t think we’ll ever be able to find out,” says Susan Martindale, volunteer manager for the English Heritage organization that manages Stonehenge.

“We have no way of understanding why people started building it – and the reasons why they continued working on it may well have changed over the centuries leading up to its construction,” she explains.

But thanks to Cox’s recent studies, we’ve learned fascinating details about one of the world’s most enigmatic places. Stonehenge served as a giant echo chamber, amplifying the sounds generated inside the circle for those inside it and blocking out the noises of those outside the circle.

This discovery has some people wondering if the monument was actually built as a ritual site for a small elite group.

This breakthrough took a decade to make. Researching “the sonic wonders of the world” 10 years ago, Cox began to wonder whether studying Stonehenge’s acoustic properties could help unlock some of its secrets.

“I realized that there was a technique in acoustics that had never been applied to prehistoric sites before, and that was acoustic scale modeling,” he says. “I’m the first to make a scale model of Stonehenge or any other prehistoric stone site.”

REPRODUCING OLD SETTINGS

Cox decided to create a 1:12 scale replica that could be tested inside the university’s semi-anechoic chamber – an almost soundproof room that absorbs virtually all noise thanks to the geometric foam that covers every surface except the floor.

To create the replica, Cox was initially given a computer model by English Heritage, which allowed him to better understand what Stonehenge looked like in its complete configuration, around 4,000 years ago.

“If you visit Stonehenge today, it’s a magnificent site, but many of the stones are missing or have fallen to the ground,” he explains. “It is [configuração] it is a specific provision. In fact, from about 2000 BC until now, it has changed a lot for about a millennium.”

In all, the process of creating 157 stones using 3D printing and modeling techniques took about six months to complete. Cox remembers that, during this period, his dining room floor was covered with bits and pieces of the project, in a tireless effort to achieve the quality of real stones at scale.

When the stones were painted gray and arranged in the correct distribution according to the computer model, the challenges of the testing process began.

“Everything is 1/12 the actual size, which means we need to test with the frequency multiplied by 12,” according to Cox. “You need to have speakers and microphones that work in these frequency ranges and they are not normally available.”

To perform each test, Cox and his team placed speakers around the rocks and played the various frequencies they were interested in measuring.

Microphones in the room collected data on how the stones affected the sound. And with mathematical processing, Cox was able to create a computer model that simulates the acoustic properties of Stonehenge and can distort the voices or music to give an idea of ​​how they would have sounded inside the circle.

The result was a surprise. Although Stonehenge has no floor or roof, the sound bounces between spaces in the stones and stays within the circle. In acoustics, this phenomenon is known as reverberation.

“We know that music is enhanced by reverb, so we figured that if music were played, it would just sound a little more powerful and impactful within the circle,” explains Cox.

One of the most notable findings from Cox’s research is the effect of stones on voice directionality.

In a natural open environment, like the grassy hill where Stonehenge was built, a person speaking with their back to the listener would only be understood about a third of the time. But the reflections from Stonehenge’s stones would have amplified the voice by four decibels, increasing the sentence comprehension rate to 100%.

These results demonstrated that Stonehenge would have allowed people inside the circle to hear each other very well, while those outside the circle would have been excluded from any ceremonies that took place inside.

Cox’s research adds new information to a growing body of evidence that Stonehenge may have been used for rituals reserved for a select group of people. One of the studies even indicated the possibility that a hedge was grown to obstruct the view of people who were not participating.

“The research definitely provides more information about how Stonehenge may have been used,” continues Cox. “Even if you turn your back, there are always reflections on the stones to reinforce your voice, so it really doesn’t matter if you can’t see the person speaking. It would be really good for speech communication.”

Cox relates Stonehenge’s acoustic properties to the difference between standing in an empty movie theater versus a cathedral.

People used to walking in and out of buildings might find the difference not very noticeable, but Cox points out that the Late Neolithic people who built Stonehenge were not used to the acoustics of large walls and enclosed spaces. They probably found the effect mesmerizing.

POWER AND FASCINATION

After Cox published his initial findings in 2020, he and his colleagues began grappling with new questions — how people inside the circle might change the acoustics, for example.

The team recently completed a new set of measurements, placing up to 100 small wooden dolls around the model.

“We know that people inside would have altered the acoustics, as we absorb sounds,” he explains. “We want to quantify what the change might have been when more people entered the circle, as there were probably people inside the circle during the ceremonies.”

This latest research also takes a closer look at how listeners heard sounds coming from different angles, as the way we perceive sound changes when it comes at us from the side or the front. Sound reflections from the sides, for example, increase the quality of music in a concert hall.

Cox hopes to publish the new findings later this year after reviewing his new dataset.

He acknowledges that unanswered questions about the real Stonehenge make it difficult to draw definitive conclusions about his work with the scale model. But he considers acoustic research to be another tool to find more indications and form a clearer picture of the site’s qualities.

“If you think about human ceremonies, they usually involve some form of sound, be it music, speech or chanting. And we know that if they really want to be heard, people should stay within the circle,” explains Cox.

“Now, the problem with acoustic archeology is that the sound disappears, so we can’t always be sure what was done there.”

While Fox’s day-to-day work focuses on improving sound for people with hearing loss, he now frequently responds to requests to discuss his Stonehenge research.

“One of the things about this work is you realize how powerful it is for people, how people really connect with it and how fascinated they are with everything to do with Stonehenge,” he says.

“I think it creates a mystique for our ancestors’ remarkable ability to create the most amazing monuments.”

read the original version of this report (in English) on the BBC Travel website.