Ancient appliance of acoustics revealed

Thu, Feb 16, 2012, 00:00

Researchers are finding increasing evidence that ancient civilisations used specific spaces and building designs to produce powerful acoustic effects.

It is likely that these places were used as ritual spaces and places where oracles communicated with the gods.

Evidence for these “auditory illusions” was offered today in a session at the American Association for the Advancement of Science’s annual meeting in Vancouver, entitled: “Archaeoacoustics: The sounds of the past”.

Early civilisations would have had no understanding of sound waves and would have had no simple explanation for unusual acoustic effects, suggested Steven Waller, who has studied dozens of standing stone sites across Britain.

A person able to cause or reproduce these effects could therefore have produced an impressive display for those coming to a ritual site, he said.

He showed how a simple auditory illusion could be created quite easily by having two matched sound sources and causing sound wave interference.

He made separate recordings of two pipers playing an identical note and then made a third recording while walking around the pipers. Instead of hearing a continuous tone, the sound rises and falls as sounds from the two recordings interfere with one another.

Miriam Kolar of the Centre for Computer Research in Music and Acoustics at Stanford University presented her examination of the 3,000 year old Chavin de Huantar site in Peru. She argues that its builders knew how to create unusual acoustic effects and constructed buildings that delivered them.

She described the site’s Lanzon monolith, which has a long corridor with an opening at the far end. This in turn looks out onto the Circular Plaza, a sunken area where a sound effect could be created.

This civilisation used conch-shell trumpets. If a conch shell is blown in the corridor it produces a very powerful blast of sound in the plaza below, she said. Her PhD thesis, which involves studying the effects, suggests the site was important for public rituals and may have been where an oracle performed and made predictions.

David Lubman, an acoustics consultant, looked at how sound could be manipulated to produce auditory effects at the Mayan Chichen Itza site in Mexico. Two locations on the site have been discovered where unusual sound effects can be achieved.

In one, a simple hand clap can be transformed into a chirp-like sound similar to that made by a bird species important in Mayan culture.