[Aztlan] Raindrop effect at all Mesoamerican pyramids?

[David Lubman]

Listeros:

David Hixson posted this item on 9/29/09 and repeated below:

Wayne Van Kirk wished me to forward this recent news article to the list...

"Mayans 'played' pyramids to make music for rain god"

http://www.newscientist.com/article/mg20327266.200-mayans-played-pyramids-to-make-music-for-rain-god.html?DCMP=OTC-rss&nsref=online-news

This 22 September New Scientist article was written by Linda Geddes. There were 40 reader comments at the NS website at last check. It is based on a paper recently published in Acta Acustica united with Acustica, DOI: 10.3813/AAA.918216

The article provides a great opportunity to add some archaeology to archaeological acoustics. Mesoamerican experts have the best resources and understanding to answer questions raised in this paper. I will attempt to describe it's acoustical thesis neutrally, withholding my own opinions.

The article is one of several papers by the authors about the "raindrop effect", so named by the second author (Declercq) who discovered it at the temple of Kukulkan at Chichen Itza in 2002. The effect is said to resemble the sound of a raindrop falling into a bucket. The sound is stimulated by footfalls on the staircase, and is heard only very close to the surface of the staircase.

A key question: Is the"raindrop effect" a feature of all Maya pyramids and all Mexican pyramids as its authors claim? (Perhaps the authors meant all staircased limestone pyramids.) 

The authors explain the sound as result of evanescent waves related to the corrugations.

One critic suggested a explanation based on a simpler heuristic, two-dimendional drum model. According to the simpler model, the raindrop effect is essentially a drum sound that would be expected on "hollow" pyramids such as the temple of Kukulkan, but not on filled or "solid" pyramids (those with airspaces beneath their staircase.) The simpler heuristic model envisions the staircase as a more or less homogeneous rectangular elastic membrane fixed at its four boundaries (two balustrades and at the top and bottom of the staircase) but free to flex when stimulated by footfalls in mid-staircase. Obviously, the staircase could not drum if there was no airspace underneath. He offered anecdotal evidence of an uynidentified pyramid (possibly at Copan) at which the raindrop sound was absent until an archaeologists tunnel was dug into it.

A simple one dimensional reduction would be a violin string or better, an elastic rod, held taught at both ends

Ths subject paper responds to the unstated criticism with new tests at Teotihuacán's pyramid of the moon which demonstrated the existence of the raindrop effect on a solid (no airspace) pyramid (?) The authors offer this as proof that the raindrop effect exists on all pyramids.

Mesoamericanists, please comment!

David Lubman
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