2nd Pan-American/Iberian Meeting on Acoustics


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Acoustical Solutions to Archaeological Mysteries at Chichen Itza’s Temple of Kukulkan



David Lubman - dlubman@dlacoustics.com

DL Acoustics

14301 Middletown Lane, Westminster, CA 92683


Popular version of paper 2pAA3

Presented Tuesday afternoon, November 16

2nd Pan-American/Iberian Meeting on Acoustics



Acoustic Archaeology


Without acoustics, archaeology is deaf. Without archaeology, acoustics is blind, and “acoustic archaeology” is merely acoustics. Clearly, convergent facts from both fields are needed for an investigation to be designated as acoustic archaeology.




Figure 1. Temple of Kukulkan at spring equinox exhibiting serpent shadow


Introduction and purpose

Historically, archaeologists have largely ignored acoustical science as a tool for archaeological discovery. This is changing with the advent of acoustic archaeology.


The study reported here, begun in 1998, employs acoustical science to study a problem that has stumped archaeologists for decades. It involves a serpent shadow that appears on the NW balustrade of N staircase of the temple of Kukulkan at Chichen Itza, Mexico. The phenomenon starts exactly at the spring equinox, and continues for about a week. The burning question: Is the equinox shadow the result of intentional design?




Figure 2. Resplendent quetzal


Despite compelling ethnographic ties linking the equinox display to ancient Maya culture, leading Mayanists have found no evidence of intentional design. Without such evidence, the pyramid’s solar orientation (responsible for the equinox shadows) is deemed a meaningless coincidence.

This paper offers evidence for intentionality of the shadow. Evidence is not proof. But, if it is sufficiently convincing, Mayanists must reverse their position and presume the shadow is intentional design.

Evidence for intentionality was found by relating a peculiar aural clue at the temple – a chirped echo –to Maya ethnohistory. The chirped echo is very similar to the call of the quetzal – the venerated bird messenger of the Maya gods, whose spectacular diving behavior at the spring equinox gives it the appearance of a flying serpent. Is the similarity of the shadow to the bird’s equinox behavior an uncanny coincidence? Or is it evidence of intentionality.


Universal cognitive impact of the chirped echo

One might have thought that public interest in the chirped echo would cool since its discovery in 1988. But interest has been sustained for many years and may even be intensifying.  Large groups assembled at the temple to see the equinox shadow often spontaneously organize into synchronized clapping choruses. Synchronized clapping strengthens echoes. For example, a group of ten identical synchronized clappers increase echo strength by 10 dB (decibels), which roughly doubles its subjective loudness. A group of 40 increases loudness by about 16 dB.


Why so much interest in the chirped echo?


The echo is almost universally interesting because of its unconscious cognitive impact on listeners. As children, we learn wordlessly that echoes are delayed replicas of the stimulus. Normally, that is the case.  Such echoes taken in stride.


Not so the chirped echo. Many find it totally unexpected, and only the rare visitor can explain why.  They may not even possess the vocabulary necessary to explain their surprise and feelings.


Given their unconscious expectation of echo behavior, it would seem unnatural, or even supernatural, for an echo to sound radically different than its stimulus. It might seem that one’s handclap was being answered by an unseen sentient being.  Anecdotal evidence suggests that hearing chirped echoes of one’s handclap sometimes evoke numinous (spiritual or spooky) responses.


Who are the responders? It has been suggested that the chirped echo may be especially impressive to individuals susceptible to or currently embracing what are termed New Age beliefs. It may be that that such people are more open to, tuned into, or welcoming of stimuli that evoke spiritual feelings. Perhaps those for whom the experience is unimpressive are seen as “muggles” by strong responders. This is an opportunity for field experiments.


An instructive and way to identify strong responders at Chichen Itza is by watching tour groups brought to the temple to hear the chirped echo demonstrated. As most of the tour group moves on to the next scheduled tourist wonder, one or two individuals stay behind to play with the echo in utter fascination.


Note that the chirped echo can evoke numinous responses in contemporary listeners, even those without cultural ties to the Maya or to other Mesoamerican cultures.  Therefore, it may be a nearly universal cognitive response. It is cognitive because it is a learned response. This learning takes place when children develop experiential knowledge of echoes. The learning that leads to impressed responses, however, seems largely independent of culture.


Maya expected to have strong cognitive response to quetzal sounds and images

Given numinous responses to the chirped echo by non-Mesoamericans, response must have been even more powerful to ancient Maya and some of the modern Maya as well, for whom the sound also has deep cultural meanings. 


As this author has often explained, the chirped echo closely matches the primary call of the quetzal, a bird with deep cultural and nationalistic meaning to the ancient Maya, and to many modern Maya as well. The quetzal was regarded as the messenger of the gods.


The equinox shadow appearing on the west balustrade of the north staircase at spring equinox strongly evokes the quetzal to highland Maya. Starting exactly at the spring equinox (mating season) the male quetzal rises one thousand feet above the forest canopy, folds its wings, and spectacularly dives straight down. While doing so, its long tail feathers undulate in the turbulence. This drama seems to be recapitulated by the descending serpent shadow. An examples showing the importance of quetzals to Maya nationalism, the quetzal appears on the national flag of Guatemala, 60% of whose native born have Maya ancestry.




Figure 3. The coat of arms on the Guatemalan national flag and its paper currencies have quetzal iconography


Acoustic evidence suggesting intentional design of the chirped echo

When the chirped echo at the temple of Kukulkan was first reported in 1998, doubting archaeologists quickly pronounced the echo “an artifact of reconstruction”, though no supporting evidence accompanied their statement.  Their assertion is easily refuted by applying elementary logic to observational (acoustic) evidence. To understand this, the reader must have some familiarity with temple geometry.


The temple of Kukulkan is a four-sided stepped pyramid. Its sides host identical long, continuous staircases reaching from the ground to the top platform. The north and west staircases were reconstructed by archaeologists (http://tinyurl.com/N-W-staircases). East and south staircases remain unreconstructed ( http://tinyurl.com/east-staircase).


All four staircases exhibit identical chirped echoes in response to handclaps. However, chirps from the unreconstructed staircases, though audible, are considerably weaker. Weakened chirped echoes are precisely what acousticians would predict from the disordered and crumbling state of unreconstructed staircases. Strong echoes are produced by orderly arrangements, and by covering stones with smooth dense plaster.




Figure 4. Reconstructed north and west staircases (above) yield the strongest chirped echoes [GNU documentation license]




Figure 5. Unreconstructed east staircase (above) and west staircase yield weaker but qualitatively identical echoes [GNU documentation license]


That the chirped echo is audible at unreconstructed staircases is remarkable. Fortunately, the rubble preserves traces of the spatial periodicity of the original staircase. A notable property of the human auditory system is its ability to identify tones in noise even at low signal-to-noise ratios. The tone detecting ability of human hearing, together with the partially preserved spatial periodicity of the shamble staircases have preserved the chirped echo.


Acoustical conclusion

 Since both reconstructed and unreconstructed staircases exhibit qualitatively identical chirps, it follows that the chirps are not artifacts of reconstruction


The chirps are qualitatively identical today. But were they present and identical many centuries ago when the temple was in active use? The answer is decisively yes, as shown below!

Proof that the original staircases exhibited qualitatively identical chirps in ancient times

Proof was found by exercising a simple mathematical model of the “impulse response” of the original staircases.  This model was reported and demonstrated by the author at the 1st Pan American/Iberian Meeting on Acoustics in 2004. Details were shown in subsequent oral presentations by the author, and in a recent conference paper in Paris ( http://tinyurl.com/Acoustics-08 ).


The impulse response method can simulate sounds heard wherever the stimulating sound (e.g., handclap) and impulse responses are known. This proof, that the chirped echo was built into the original design of the temple of Kukulkan, may be the first successful application of impulse response methods to acoustic archaeology.


(An elementary discussion of impulse response methods with application to acoustic archaeology at Stonehenge, by acoustician Trevor Cox, appears in the magazine New Scientist, 27 August, 2010.)


The acoustical argument shows decisively that the chirped echo was present in the original design.


This line of argument may suggest, but does not and cannot prove intent by its ancient designers.  How to do so? Enter archaeology (and by extension, cultural anthropology)



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