Sound Reflection

I'll try to collect some info on sound reflection.

I just came back from trip to Mexico. We visited the ancient Mayan city of Chichen Itza.

On my first visit to the Mayan ceremonial city of Chichen Itza in January 1998, I discovered that an echo from the staircase of an ancient temple may prove to be, in effect, an intentional sound recording. I am an acoustical scientist and Chichen Itza has long been known for acoustical anomalies. So, when I went on vacation [AW1] in the northern Yucatan where the city’s ruins are located, I took along some simple portable sound instruments and a digital tape recorder.



The site’s most famous structure is its massive limestone temple in the form of a truncated pyramid. Named El Castillo (the Castle) by the Spanish conquistadors arriving centuries after the Maya had mysteriously abandoned the city and returned to the Guatemalan jungles, the pyramid dominates the open, grass-covered plaza on which it resides. On each of its four sides a steep staircase leads up to a small temple on the summit. Two of these staircases are restored. Many climbers who reach the top find that the steps’ unusually high risers and narrow treads make for a treacherous descent.



If you stand in front of El Castillo and clap your hands, you will hear a remarkable echo—a distinct chirp that swoops downward in pitch by almost an octave. Tour guides and tourists like to clap their hands to hear the echo, greatly annoying the archaeologists working there.



I stood in front of the temple and, like other tourists, clapped my hands and marveled at the echo. Unlike other tourists who listened and promptly forgot, I sensed that this echo was more than just a “mystery” to tantalize tourists. I made tape recordings of the initial impulse (the handclap) and the resulting chirped echo and noted the amazing similarity of this echo with the call of the sacred quetzal bird.

This description is accurate and it's from relatively old article "On the Ancient Origins of Sound Sculptures" by David Lubman and Brenda Kiser.

It's truly an amazing phenomenon for a physisist to observe. Our tour guide, Alfredo, said that he's going to clap in front of the pyramid and that it will echo as an eagle's cry. I thought it'll vaguely resemble some bird sound, but the effect was very impressive. It actually sounded like eagle cry to me. All our group clapped together with a giude, and it was much louder. He suggested that in ancient times they would gather hundreds people and do it together.

I was thinking about the explanation all this time and thought that I found one. Google search gave me the following links. I ordered some articles through our library. If the explanations are different from mine, then I'll go ahead and proceed with my own simulation. I was going to record a clap at home, then pass it through a certain transformation based on my theory of the phenomenon, then compare the results with recorded quetzal's chirp. That's the plan for a next week.

David Lubman's research

THE ACOUSTICS OF MAYAN TEMPLES by WAYNE VAN KIRK

Archaeological acoustic study of chirped echo from the Mayan pyramid at Chichen Itza, in the Yucatan Region of Mexico ... Is this the world's oldest known sound recording?



Repetition Pitch glide from the step pyramid at Chichen Itza

A theoretical study of special acoustic effects caused by the staircase of the El Castillo pyramid at the Maya ruins of Chichen-Itza in Mexico.

Archaeological acoustic study of chirped echo from the Mayan pyramid at Chichén Itzá (A)

A full simulation of the Quetzal echo at the Mayan pyramid of Kukulkan at Chichen Itza in Mexico (A)

Theoretical interpretation of a case study: Acoustic resonance in an archaeological site (A)