Aaron Watson Archaeology Research
Standing Wave Resonance
Standing waves are an acoustic effect that occurs at many enclosed monuments, including Camster Round and Maeshowe. They are produced as sound waves interact while being reflected between walls. These waves are either enhanced or cancelled, significantly changing the nature of the sound. The effect is most apparent with continuous notes or tones, and can be generated with either the voice or musical instruments.
To generate standing waves, the pitch of continuous notes or tones is gradually adjusted until a distinct change is heard. The sound then expands to create a rich ‘landscape’ of sound that can be explored by the listener.
As the listener passes through the complex patterns of interacting sound waves, there can be some rather extraordinary effects. The sounds might become louder with distance from the source, for example, or even disappear altogether. Some frequencies even resonate parts of the body. Sounds can become detached from their source and move around the chamber. It is even possible to hear the movements of other people within the monument as their body mass induce subtle modifications upon the waves.
Interpreting Standing Waves
In the modern world we can rationally explain standing waves, but this is unlikely to have been a Neolithic understanding. Acoustic physics is largely founded upon 19th and 20th century theories of sound waves, and the mathematical principles that underlie them.
Instead, we need to imagine how the people who built and used stone monuments might have understood such effects. Standing waves have been recorded at a variety of ancient sites by Paul Devereux and Robert Jahn, who suggested that the effect could be evoked by ritual chanting.
See their paper: Devereux, P. and Jahn, R.G. 1996. Preliminary investigations and cognitive considerations of the acoustical resonances of selected archaeological sites. Antiquity 70: 665-6.