The outer sarsen circle at Stonehenge.
Acoustics at Stonehenge
Stonehenge was constructed over many centuries. During this time its appearance changed significantly and so did its acoustic properties. While it is difficult to reconstruct the behaviour of sound in Stonehenge's earlier phases when it was mostly constructed using timber posts, it is possible to explore the monument as it stands today. Although many stones have fallen or been removed altogether, this arrangement was constructed between 2500 and 1600 BC.
In collaboration with acoustician David Keating, the first acoustic exploration of Stonehenge was conducted in 1998. An omni-directional loudspeaker was placed at the centre, and a series of measurements recorded along a straight line leading out towards the Heel Stone and Avenue.This revealed the fundamental sonic properties of the monument.
David Keating (left) and me conducting archaeoacoustic fieldwork along the primary axis of Stonehenge in 1998. The results of these recordings show how the standing stones enhance the behavior of sound in contrast to a control recordings made in an open environment.
Interpreting the acoustics of Stonehenge
The contrasting acoustic experiences between the inside and outside of Stonehenge may have restricted the number of people who could fully participating in activities at the centre. An audience outside the monument would not have clearly seen or heard events within and, as the higher frequency sounds are blocked by the stones, the sounds they heard may have been unusual and distorted. In contrast, an audience occupying the confined interior would have heard amplified sound, and this was especially effective for voices. Fieldwork also revealed that the size and close spacing of the sarsens allows resonances to form.
David Keating (on the left) and me undertaking acoustic fieldwork at the centre of Stonehenge. This view emphasises how the outer sarsen circle blocks both sound and vision.
Many thanks to Historic England (formerly English Heritage) for permission to conduct fieldwork at Stonehenge.
Further reading
Watson, A. 2006. (Un)intentional sound: acoustics and Neolithic monuments. In G. Lawson and C. Scarre (eds) Acoustics, space and intentionality: identifying intentionality in the ancient use of acoustic spaces and structures. McDonald Institute for Archaeological Research Monograph.