[Aztlan] Plaster and the general geology of the YukatanPeninsula

[David Lubman]

Last week, Dave wrote:

 >I've often thought that Wayne (he meant this writer, David Lubman) and Greg Sandor (fellow
> listeros) should link up to conduct some VR simulations of acoustical
> properties (e.g., shooting a laser or other item with a known trajectory
> to evaluate its reflective properties depending upon the location of the
> FPS).  Greg could easily add or subtract the now-fallen exterior walls to
> determine the effect upon acoustical vectors.
>
> Love to hear more.
>
OK Dave. Here's a little more about the role of computer simulation.

Architectural acoustic simulation and auralization have long been a hot area in acoustics research. Acoustic simulation and auralization of ancient theaters has become fairly routine in Europe. Mesoamerican researchers will not have read much about these developments on Aztlan.  So I appreciate this opportunity.

Many papers on simulation and auralization of ancient theaters were presented at the recent Acoustics '08 conference in Paris. Most were in a special session on archaeological acoustics that I organized with two European colleagues. One of them, Jens Holger Rindel http://www.odeon.dk/?q=node/1, is particularly active in this field through Odeon, one of several developers of commerical acoustical simulation software.

Despite continuing improvement of that software, measurement, analytical, and heuristic acoustic modeling retain an important place in architectural acoustic research.

My heuristic model for the whispering gallery in the Great Ball Court (GBC) employs "strength factors" to account for sound reinforcement by the temples at each end. According to my current model, their reflective strengths are modest. Far too modest to account for the whispering gallery of the present structure. It would be very valuable for my modeling if I were permitted to measure their present values.

Acoustically, the end temples are essentially theater stages. A widely accepted procedure allows the strength factor, G, in dB (decibels) of theater stages to be determined by measurement. One respected authority* defines the Strength Factor G as:

"A measure of the sound pressure level at a point in the hall, with an omni-directional source on the stage, minus the sound pressure level that would be measured at a distance of 10 m from the same sound source operating at the same power level and located in an anechoic chamber."

*How they Sound - Concert and Opera Halls, Leo Beranek, Appendix 2, p 574, pub. for the Acoustical Society of America by the American Inst. of Physics (1996).

I realize that the temple architecture has changed, for example, because the roofs have collapsed. However, determination of the present G Factors would usefully inform a simulation model to "predict" G for intact temples. The sensitivity of G to incremental architectural changes can also be estimated with the simulation model.

In acoustics as in many other scientific fields, the public tends to believe anything that comes out of a computer, because computers are magical. Veterans know that measurements are useful for guiding the computer simulation. More often than the public realizes, computer simulations are tweaked to agree with measurements.

The point of all this is to use acoustics in the service of archaeology. 

Best regards,

David Lubman, FASA
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http://www.acoustics.org/press/152nd/lubman.html

http://dsc.discovery.com/news/2006/11/27/whispering_arc.html