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Scientists turn to ‘laser accurate’ model to test Stonehenge acoustics

Salford team explores sound qualities of ancient Wiltshire monument using 1:12 replica based on data from scans

A diminutive model of Stonehenge could help crack the acoustic secrets of the ancient site, according to scientists who have built a version of the megaliths at a 12th of their size.

The team say the 1:12 model, with a stone circle spanning 2.6 metres, has an edge over other replicas of Stonhenge, such as the full-scale one near Maryhill,Washington, for being based on laser scan data. The data collected by Historic England allowed the team to produce a highly accurate representation.

The problem with the other models we have is that the stones arent quite the right shape and size, and how 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. Those blocks at Maryhill are all very rectangular, whereas real Stonehenge, when you look at it, they are all a bit more amorphous because they are made out of stones that have been hand chiselled.

The new model also allows the team to remove or replace stones and see how the acoustics of the site would have altered. We are taking out the stones in phases so we can look at what effect each individual element has on it, said Cox.

The team used insights from archaeological work by other experts to reproduce the set-up of the pre-historic monument as it would have looked about 4,000 years ago, including stones now missing. While fewer than 100 stones remain today at the Wiltshire site, the teams model has 157.

While construction of the model could not compare with the building of the real Stonehenge, it was nonetheless a bit laborious, said the team. You 3D print them and then you make silicon moulds out of them, and then you cast them in a plaster-polymer mix, and then you paint them in car paint, Cox said. I ruined my dining room floor.

Prof
Prof Trevor Cox with the scale model of Stonehenge. Photograph: Andrew Brooks/University of Salford

The team conducted tests with the model set inside an acoustic chamber, looking, for example, at speech intelligibility and air resonance. Preliminary data had already given interesting results while the reverberation time for high- and mid-frequency sounds appeared similar to results obtained from Maryhill, low-frequency sounds showed shorter reverberation times. If you were to talk in a cinema, that is probably roughly the acoustic we are getting, said Cox.

He added that as well as being visually striking the auditory environment of Stonehenge would have been unusual to prehistoric people of the time less familiar with reverberant spaces unless, for instance, experiencing such effects in a cave. There would have been a sonic wonder in the past, he said.

While the purpose of Stonehenge has fuelled much debate, Cox says he thinks the acoustics were a byproduct of the structure which were then exploited. If you were going to hold a ceremony, and you had a lot of people to talk to, doing it outside the stones would be a lot harder than if you did it inside the stones [circle], he said.

At about 40cm high, the model megaliths are almost exactly the same size as the Lilliputian props featured in the famous Stonehenge scene in the film This Is Spinal Tap. They are also at similar risk of being crushed underfoot. You have to be careful when you stand over this thing you dont kick the lintels off, which I have done once already, said Cox.

Cox said plans for where the teams mini megaliths will end up remain unclear. It would be nice to find a permanent home for it, maybe in a museum somewhere, he said. The boring answer is in the short term it will go back in boxes to be stored very carefully.

Read more: https://www.theguardian.com/uk-news/2019/jul/11/scientists-turn-to-laser-accurate-model-to-test-stonehenge-acoustics

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