Scientists Map Stonehenge’s Soundscape

A new analysis of a small-scale acoustic model of Stonehenge suggests that people who spoke or played music inside of the ancient monument would have heard noticeable reverberations, reports Bruce Bower for Science News. The findings are published in the October issue of the Journal of Archaeological Science.

To assess the prehistoric circle’s amplifying effects, scientists at the University of Salford’s Acoustic Research Center 3-D-printed 27 unique stones measuring one-twelfth of the originals’ size. Then they used silicone molds and plaster to create copies of the rocks, stopping upon reaching 157 total, or the estimated number of standing stones present at Stonehenge some 4,200 years ago. Finally, the team tested the model in a room with walls that absorbed sound to gauge how the blocks reflected noise and created a unique acoustic experience.

Four-directional speakers placed in five locations around the model—which lead author and acoustical engineer Trevor Cox dubbed “Stonehenge Lego,” according to Science News—chirped out a range of high pitches. (The team used pitches at twelve times the frequency of normally experienced noises because the sound waves had to be shrunk down to scale, just like the model monument.)

Microphones placed across 20 locations in and around the model, meanwhile, showed that sounds reverberated longer inside the stone circle than outside of it. In other words, writes David Keys for the Independent, Stonehenge “acted as a giant amplifier,” making it easier for individuals visiting the monument to hear conversations or music performed within the structure. On the flipside, the researchers point out in their paper, the circle’s acoustics would have kept noise from the surrounding landscape out—and made it difficult for passersby to overhear what was happening inside.

“The results show that music, voices or percussion sounds made at the monument could only really be heard by those standing within the stone circle, suggesting that any rituals that took place there were intimate events,” says co-author Susan Greaney, an archaeologist at the University of Cardiff and historian at English Heritage, in a statement. “It’s exciting to see how modern techniques of laser scanning, 3-D printing and acoustic modelling can tell us about the distant past.”

Cox and his colleagues found that sound reverberated in Stonehenge Lego for at least 0.6 seconds, and closer to 0.8 seconds at lower frequencies. For comparison, sound reverberates for just under half of a second in a normal living room and for around eight seconds in a cathedral, per Science News.

The team’s reverberation time was noticeably longer than those recorded in previous studies of a concrete Stonehenge replica in Maryhill, Washington state.

“The problem with the other models we have is that the stones aren’t quite the right shape and size, and how the sound interacts with the stones depends critically on the shapes,” Cox told the Guardian’s Nicola Davis in 2019. “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 chiseled.”

Though Stonehenge’s ancient visitors likely experienced noticeable reverberation within the completed monument, the study’s authors emphasize that acoustic innovation probably wasn’t its Neolithic builders’ primary goal. Historians don’t know exactly why Stonehenge was created, but its alignment with astrological phenomena and signs of use as a cemetery point toward a ceremonial past.

“Constructing and testing the model was very time consuming, a labor of love, but it has given the most accurate insight into the prehistoric acoustics to date,” says Cox in the statement. “With so many stones missing or displaced, the modern acoustics of Stonehenge are very different to that in prehistory.”

Future research may examine other aspects of Stonehenge’s acoustic characteristics, including the kinds of echoes it creates and the way that its stones hum in strong winds.

The new study “shows that sound was fairly well contained within the monument and, by implication, [Stonehenge] was fairly well insulated from sounds coming in,” Timothy Darvill, an archaeologist at Bournemouth University, tells Science News.

Listening to the sounds reverberating “must have been one of the fundamental experiences of Stonehenge,” he adds.

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Theresa Machemer is a freelance writer based in Washington DC. Her work has also appeared in National Geographic and SciShow. Website: tkmach.com