From the Telegraph via Daily Swarm:

Mr Till, an expert in acoustics and music technology at Huddersfield University, West Yorks., believes the standing stones had the ideal acoustics to amplify a “repetitive trance rhythm”.

The original Stonehenge probably had a “very pleasant, almost concert-like acoustic” that our ancestors slowly perfected over many generations

And there's a Washington connection:

The most exciting discoveries came when he and colleague Dr Bruno Fazenda visited a full-size concrete replica of Stonehenge, with all the original stones intact, which was built as a war memorial by American road builder Sam Hill at Maryhill in Washington state.

Although the replica has not previously gained any attention from archaeologists studying the original site, it was ideal for Dr Till's work.

He said: "We were able to get some interesting results when we visited the replica by using computer-based acoustic analysis software, a 3D soundfield microphone, a dodecahedronic speaker, and a huge bass speaker from a PA company.

"By comparing results from paper calculations, computer simulations based on digital models, and results from the concrete Stonehenge copy, we were able to come up with some of these theories about the uses of Stonehenge.

"We have also been able to reproduce the sound of someone speaking or clapping in Stonehenge 5,000 years ago.

"The most interesting thing is we managed to get the whole space (at Maryhill) to resonate, almost like a wine glass will ring if you run a finger round it.

And finally, some footage of their research: