So this is pretty wild. We've heard our fair share of radical explanations for the mysterious layout of Stonehenge's iconic boulders, but we've never heard one quite like this. A new theory maintains that the prehistoric architects of Stonehenge were inspired by patterns of acoustic interference, which the builders would have regarded as "magical auditory illusions."
The theory is being championed by U.S. scientist Steven Waller, who specializes in archaeoacoustics — a research field dedicated to the acoustics of archaeological sites and artifacts, with a particular emphasis on prehistoric music.
Based on his independent research, Waller claims that the arrangement of the stones match up with the regular spacing of constructive and destructive audio interference, which Stonehenge's planners may have heard in the presence of two instruments playing the same note simultaneously.
The Guardian's Ian Sample writes:
In Neolithic times, the nature of sound waves – and their ability to reinforce and cancel each other out – would have been mysterious enough to verge on the magical, Waller said. Quiet patches created by acoustic interference could have led to the "auditory illusion" that invisible objects stood between a listener and the instruments being played, he added.
To investigate whether instruments could create such auditory illusions, Waller rigged two flutes to an air pump so they played the same note continuously. When he walked around them in a circle, the volume rose, fell and rose again as the sound waves interfered with each other.
"What I found unexpected was how I experienced those regions of quiet," Waller told Sample. "It felt like I was being sheltered from the sound. As if something was protecting me. It gave me a feeling of peace and quiet."
Waller then recruited volunteers, blindfolded them, led them in a circle around the instruments, and asked them to sketch out any obstacles they thought might have been positioned between them and the flutes while they were ushered around the instruments. Many of the volunteers drew pillars. One even drew an archway.
If you've ever seen concentric ripples originating from two nearby points in a pond, then you have an idea of the type of interference pattern Waller is talking about. For him, this pattern — taken together with his independent research — is enough evidence to assume that "the stones of Stonehenge cast an acoustic shadow," a theory he described at a meeting of the American Association for the Advancement of Science in Vancouver. But others aren't convinced.
"The main structure is a replica in stone of what was normally built in wood," explained archaeology professor Timothy Darvill. "They used the same techniques. The positioning of the main components is all about the construction of a framework, a building if you like..."
A cool idea? Definitely — but it still feels like a reach... and it'll probably take more compelling evidence if Waller wants it to gain any serious traction.