The view across the standing stones at Avebury from the top of the earthwork 'henge'.
Acoustics at Avebury
This enormous monument is poorly preserved, and much of what we see today was re-constructed by Alexander Keiller in the 1930s. To consider how sound might have moved around this vast arena of earth and stone, we have to see through the confusion of medieval buildings, fences and a modern roads.
Archaeoacoustic fieldwork is possible where original fragments remain. In 2001, John Was used noise generators to explore how Avebury's earthwork henge influences the movement of sound. While much of the ditch has silted up, sections of the bank stand several metres high and seem to be reasonably well preserved. It was possible to demonstrate that sounds made inside the henge could not have been clearly heard from outside, as they are blocked and filtered these earthworks. In the same way, sounds in the wider landscape would be difficult to hear inside the monument.
For an audience excluded outside the henge, events taking place within would have been obscured both visually and audibly, potentially creating a sense of mystery.
The standing stones
Inside Avebury's earthwork are large standing stones that can reflect sound. An especially interesting feature is the Cove, an open-sided arrangement of three large monoliths. This would have allowed sound to project out in one direction while mostly being blocked in others. It seems possible that the Cove could have acted rather like the stage in a theatre by creating a visual backdrop and enabling voices and other sounds to be more clearly audible from certain directions.
Two views of the Cove within Avebury
There are three stone circles with the henge at Avebury, and the two Inner Circles may have been the most acoustically dynamic. While this is difficult to measure today because of medieval buildings and trees inside the henge, parallel experiments at the Ring of Brodgar in Orkney have shown how a circular arrangement of standing stones is very effective at generating echoes. In addition, archaeologists have noted that the stones chosen for the two Inner Circles at Avebury are larger and broader than those used elsewhere, improving their potential to reflect sound.
Stones of the Southern Inner Circle within Avebury.
An interesting acoustic quality of circular spaces is the way in which echoes change in relation to the locations of the listener and the sound source. If both are close to the centre, sounds will be reflected simultaneously from all sides of the circle and return as a coherent echo that surrounds the listener. Away from the centre, echoes become irregular and indistinct as sounds reflecting from the perimeter stones return at different times. This creates an acoustic focus within each circle.
The idea of an acoustic focus is interesting because the central areas of both the Inner Circles at Avebury are distinguished by unusual stone settings where people might have gathered. The centre of the northern Inner Circle is marked by the Cove (see above), while the southern Inner Circle was the setting for one of the largest stones at Avebury, the Obelisk, which has sadly not survived.
Watson, A. 2001. Composing Avebury. World Archaeology 33(2), 296-314.