Scientists have known for a long time that sound waves coming from opposite directions can cancel each other out, creating areas of relative quiet. This is not just a laboratory effect, but can be observed, for example, if two pipers play their pipes as they walk around a field.

Now an acoustic researcher has theorized that the unusual layout of the ancient uprights at Stonehenge was designed to mimic this effect. Steven Waller of Rock Art Acoustics USA laid out his theory about the monument before the American Association for the Advancement of Science on Thursday.

Waller described an experiment in which blindfolded test subjects walked into a field where two pipers were playing and were asked to report whenever it sounded as though there was a barrier between them and the music. The result was that "they drew structures, archways and openings that are very similar to Stonehenge."

Waller did not choose pipers for his experiment arbitrarily. He notes that stone circles are traditionally known in Great Britain as "piper stones" and also cites a legend that "Stonehenge was created when two magic pipers led maidens into the field to dance and then turned them to stone."

Waller is part of the growing science of what is known as "archaeoacoustics," the study of the ancient utilization and manipulation of unusual sound effects at sacred sites. Another current article on the subject describes recent findings at the Peruvian ceremonial center of Chavín de Huántar.

According to the leader of that study, "At Chavín, we have discovered acoustic evidence for selective sound transmission between the site's Lanzon monolith and the Circular Plaza: an architectural acoustic filter system that favors sound frequencies of the Chavín pututus [conch-shell trumpets] and human voice."

The article explains that "central to the purpose of this careful arrangement of sound and architecture and the resulting dynamics is the sensory effect that the sound is designed to have on humans within earshot, which some scholars theorize creates the intended "state of mind" for religious or worshipping purposes."

In other words, the intention was to use a combination of sound and stone architecture to produce altered states of consciousness. Perhaps that was the function of the carefully chosen and positioned rocks at Stonehenge, as well.

Photo by Danny Sullivan from Flickr