Was Stonehenge designed for sound?

The BBC and New Scientist Report–A team of academics have revealed the “sonic experience” that early visitors to Stonehenge would have heard. Acoustic archaeology: The secret sounds of Stonehenge

Just after sunrise on a misty spring morning last year, acousticians from the University of Salford, Bruno Fazenda, and Rupert Till of the University of Huddersfield, UK, could be found wandering around Stonehenge popping balloons. This was not some bizarre pagan ritual. It was a serious attempt to capture the “impulse response” of the ancient southern English stone circle, and with it perhaps start to determine how Stonehenge might have sounded to our ancestors.

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Salford’s Dr Bruno Fazenda said they had found the site reacted to sound “in a way that would have been noticeable to the Neolithic man”. He said the research would allow a “more holistic” view of its past. The acoustic experiments could not be carried out at Stonehenge, as the derelict state of the site meant only a “few weak echoes and no noticeable reverberation” could be studied. As a result, the team used a full-sized concrete reconstruction of it in Maryhill, America, which was built in 1929 as a memorial to WWI soldiers.

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An impulse response characterises all the paths taken by the sound between its source – in this case a popping balloon – and a microphone positioned a few metres away. It is simply a plot of the sound pressure at the microphone in the seconds after the pop. The first, strongest peak on the plot represents the sound that travelled directly from the source to the microphone. Later, smaller peaks indicate the arrival of reflections off the stones. The recording and plot shows the impulse response Bruno and Rupert measured with a microphone positioned at the centre of Stonehenge and a popping balloon at the edge of the circle.

This impulse response represents an acoustic fingerprint of the stones. Back in the lab, it can be used to create a virtual rendition of any piece of music or speech as it would sound within the stone circle. All that is needed is an “anechoic” recording of the raw music or speech – a recording made in a reflection-free environment such as the open air or, better, a specialist anechoic chamber such as we have at Salford. The anechoic recording and the impulse response can then be combined using a mathematical operation called convolution.
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“We thought that doing this would bring an element of archaeology that so far hasn’t been looked at.

“This type of research is important because now we can not only see ourselves surrounded by the stones using virtual reality, but we can also listen how the stone structure would have enveloped people in a sonic experience. It is as if we can travel back in time and experience the space in a more holistic way.”

Dr Fazenda said that the data collected did not “unequivocally reveal” if the site was designed with acoustics in mind, like a Roman amphitheatre. But he added that it did show “the space reacted to acoustic activity in a way that would have been noticeable to the Neolithic man”.

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