New research offers “Soundhenge” discoveries

SALISBURY, England – Pagans in the U.K. who regularly do rituals at Stonehenge have often commented on the unusual acoustics at the site: there seems (anecdotally) to be something about the henge which is conducive to conducting sound in a particular way.

Druids at Stonehenge

Inside the circle, it’s easy to hear what people are saying, but those who have (for whatever reason) remained outside the henge itself say that even quite loud rites are barely audible – even though the monument today is very different to how it would have looked when it was intact, due to erosion and damage. Obviously, many of the original stones have now fallen.

Lately, the scientific and archaeological establishment has turned its attention to this issue, and further interest has been provoked in this ancient monument by the discovery of the shafts around the site

New research, reported in the October Journal of Archaeological Science, has recently been undertaken by acoustics engineers led by Professor Trevor Cox from the University of Salford, and it suggests that the huge stones behave rather like an amplifier.

This increases the decibel count of sounds generated within the henge by between 10% – 20% (this is up to 10 decibels, described as a “significant increase” in sound pressure), in comparison to less enclosed environments. Even though the henge almost certainly did not possess a roof, sounds inside the circle seem designed to be much less audible to those standing outside it, just as ritualists have reported.

Researchers made a 1:12 scale model of the henge as it would have looked when it was still intact: based on a model provided by Historic England, who are responsible for the upkeep of the monument. The model, created via silicon moulds and a 3D printer, was as large as possible given the size of the testing chamber. The precise surface topography of each stone was recreated, to provide as accurate a test as possible, and acoustic testing techniques, usually used on scale models of theatres and opera houses, were then applied.

The researchers found that sounds – represented by a series of chirps moving from low to high frequencies – lingered within the henge, so the structure would have enhanced voices, for example. There was no echo. In general, reverberation time is in the region of 0.4 seconds in a living room, around 2 seconds in a concert hall and about eight seconds in a large space such as a cathedral. In the henge, it is estimated to have been around 0.6 seconds.

“Constructing and testing the model was very time consuming, a labour of love, but it has given the most accurate insight into the prehistoric acoustics to date. With so many stones missing or displaced, the modern acoustics of Stonehenge are very different to that in prehistory,” says Professor Cox.

We do not know exactly what kind of rituals were conducted at the henge. The people who built it were an oral culture: they did not write anything down, and thus our theories about them must remain in the realms of extrapolation and speculation. However, we do know that both drums and wind instruments were used in Europe at this time and it is reasonable to posit that some kind of instrument may have been used in Stonehenge, along with the human voice.

The new findings on the acoustics suggest that ceremonies in the henge were intended for participants only, and were not designed to be heard far outside the circle itself. Any instrument producing a strong reverberation, such as a drum or the big bronze horns known as ‘lurs,’ would have been particularly effective for generating sound effects within the circle. 

These new findings do not answer all the questions that have been posed about the acoustics of Stonehenge, but ‘Soundhenge’ has proved a talking point among those Pagans who have experienced the acoustics of the site, and those scientists who have done research into the monument and its soundscape before, such as musicologist Rupert Till of the University of Huddersfield.

He says that further research is required into echo effects and into the “Stonehenge hum” – a feature noted in the monument in strong winds. Archaeologist Timothy Darvill of Bournemouth University says that the new research shows that “sound was fairly well contained within the monument and, by implication, [Stonehenge] was fairly well insulated from sounds coming in.”

Moreover, researcher Andrew Collins, along with chartered engineer Rodney Hale, has recently been undertaking research into the newly discovered shafts around the monument.

Collins says, “”Rodney Hale suggests that for the pits to function as sound resonators the deliberate introduction of wind would have been necessary. Wind crossing the lip of a shaft inducing the so-called Helmholtz effect would have generated oscillations or vibrations, with air traveling to the bottom and back up again reinforcing this process. The efficiency of such structures could have been enhanced by the creation of a roof-like feature with holes (like the design of an ocarina), or by the introduction of instrumentation. This might have included rhythmic drumming, the sounding of horns, the presence of cords strung between posts catching the wind, or the employment of bullroarers.”

The research carried out by Collins and Hale is ongoing and likely to produce further theories about the role of these mysterious shafts in the Stonehenge landscape.

The U.K. Pagan community has responded to the new research with interest: Druidic groups, in particular, regularly undertake rituals at the henge and may be inclined to do some experimentation of their own with the acoustics, now that we know a little bit more about them.

The Pagan community is also following the research into the Durrington shafts: the most recent big discovery of the henge landscape.

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