Science: ancient soundscapes

Lanzon Gallery at Chavin, Physics Today

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This headline, "Uncanny acoustics at a Peruvian archaeological site," at AIP's Physics Today caught my attention because it's unusual to hear a scientist use the word uncanny.

According to Encyclopedia Brittanica architectural acoustics is known to have been studied and applied for 2000 years. Miriam Kolar's research as part of the Chavín de Huántar Archaeological Acoustics Project has pushed the knowledge envelope back a thousand years. Similar research has been done at Stonehenge. In fact you can purchase apps for Apple and Android in which reproduce conditions there.

Below is a video illustrating the sound dynamics of Stonehenge, posted by Rupert Till.

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Returning to the Peruvian archaeological site, Kolar describes the effects of the chamber:

Present-day pututu musicians playing in the narrow, stone-lined corridors, alcoves, and rooms of Chavín have reported sensing their instruments “pulled into tune,” almost as if an unseen presence were guiding their playing. If two musicians blow on their shell horns close together, they may sense their instruments coming into sync with each other. What could account for that seeming phantom force?

While playing a shell horn, a musician’s lips vibrate in sync with the oscillations of the air in the shell’s spiraled interior. A player can modify the instrument’s tone by increasing the frequency of his or her lip vibrations, changing the shape of the air column inside the instrument by inserting a hand in the shell’s opening, or changing the shape of the vocal tracts. Those actions are all intuitive performance techniques.

Kolar explained that the small, enclosed spaces inside Chavín’s massive stone buildings have strong naturally occurring resonance frequencies, which can couple with the resonance of the pututu and the musician’s own lips and vocal tract. The acoustic coupling guides the musician and the instrument into a matching sound with the room. Both musician and listeners sense the eerie effect.

This is an ancient pututu. Note that it's modelled after a large conch shell.

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Chavin pututus, Stanford Chavín de Huántar project

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Acoustic couplers like the one below were used in the early days of using modems to connect to a network. And resonance is a powerful effect, known to bring down bridges.

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Acoustic Coupler, Wikimedia

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--Marge