A model of Stonehenge could help pierce the acoustic secrets of the ancient site, according to scientists who built a version of the megaliths at one-twelfth of their size.
The team stated that the 1:12 model, with a 2.6-meter stone circle, had an advantage over other replicas of Stonhenge, such as the large-scale replica located near Maryhill, in the state of Stonhenge. Washington, because of its laser scanning data. The data collected by Historic England enabled the team to produce an extremely accurate representation.
"The problem with the other models we have is that the stones are not quite the shape and the size, and the way the sound interacts with the stones depends critically on the shapes" said Trevor Cox, professor of acoustic engineering at the University of Salford and part of the team. "The Maryhill blocks are all very rectangular, while the real Stonehenge, when you look at it, is a bit more amorphous because they are made of hand-carved stones.
The new model also allows the team to remove or replace the stones and see how the acoustics of the site would have changed. "We remove stones in stages so that we can examine the effect of each individual element on it," said Cox.
The team exploited the knowledge gained from archaeological work conducted by other experts to replicate the prehistoric monument organization, as it might have been 4000 years ago, including the missing stones. There are less than 100 stones left on the Wiltshire site, but the team's model has 157.
Although the construction of the model can not be compared to that of the real Stonehenge, it was nevertheless a little laborious, said the team. "You print them in 3D, then you make silicon molds, then you incorporate them into a mix of plaster and polymer, then you paint them with car paint," said Cox. "I ruined the floor of my dining room."
The team conducted tests with the set of models inside an acoustic chamber, examining for example speech intelligibility and airborne resonance. Preliminary data had already yielded interesting results – although the reverberation time of high and medium frequency sounds is similar to Maryhill's, low frequency sounds show shorter reverberation times. "If you were to speak in a movie theater, it's probably basically the acoustics we get," Cox said.
He added that the auditory environment of Stonehenge would have been unusual for prehistoric men less and less familiar with reverberant spaces, unless they experienced such effects in a cave. "There would have been a sonic wonder in the past," he said.
While Stonehenge's goal has fueled many debates, Cox says that he thinks that acoustics is a byproduct of the structure that was later exploited. "If you had to organize a ceremony and you had a lot of people to talk to, doing it outside the stones would be much more difficult than if you were doing it in the stones [circle]," he said.
At about 40 cm high, the megalith models are almost exactly the same size as the Lilliputian accessories featured in the famous Stonehenge scene from the film This Is Spinal Tap. They also run the same risk of being crushed underfoot. "You have to be careful when you stick to lintels, which I've done once," Cox said.
Cox said the plans for the team's mini-megaliths remain unclear. "It would be nice to find a permanent home for this, maybe in a museum somewhere," he said. "The answer is boring, it's that in the short term, it will be stored in boxes very carefully."