Visitors to the Mayan Temple of Kukulkan at Chichen Itza in Central Mexico have long been fascinated by an unusual sound effect of the ancient structure: A mere handclap at the bottom of one of the massive staircases produces a piercing echo, similar to a shriek. To some, the echo sounds eerily like the call of the quetzal, a brightly colored exotic bird native to the region and prized for its long, resplendent tail feathers. The echo effect is so pronounced that it has raised a provocative question: Could the Maya have deliberately designed the pyramid to emit the distinctive sound?
Until recently, this question seemed unanswerable. How, after all, does one prove intent when the architects of a building have been dead for a millennium? But thanks to an emerging new field -- acoustical archaeology -- it may now be possible to shed new light on this and other enduring mysteries once thought to be irretrievably locked in the past. Taking a literal riff on the German poet Goethe's reference to architecture as "frozen music," acoustical archaeologists believe important information about the past can be gleaned from the acoustics of ancient structures.
The unusually sophisticated acoustics of Mayan temples have puzzled visitors for years. And understandably so: In the Great Ball Court at Chichen Itza -- 545 feet long and 225 feet wide -- a whisper at one end can be heard clearly at the other. But sound is an aspect that, until now, has largely been ignored by archaeologists. Nor have acousticians taken much interest in work usually done by archaeologists. But the traditional boundaries that have kept the two fields apart are beginning to blur as a handful of respected acousticians apply their expertise to such acoustical phenomena.
Among them is David Lubman, an acoustical consultant in Westminster, Calif., who frequently serves as an expert witness in civil and criminal trials. That's his bread and butter. His passion is studying the strange acoustical effects of ancient Mayan architecture, particularly at Chichen Itza, a former Maya-Toltec city in the northern Yucatan region of Mexico. Intrigued by the debate surrounding the mysterious chirped echo, he is the first to make scientific measurements of the echo and provide a scientifically credible explanation of its cause.
The science behind the sound turns out to be quite simple. Staircases are periodic elements -- that is, they are repeated at regular intervals in a region of space. The gaps in the step faces constitute a diffraction grating, causing a series of periodic sound-wave reflections, or tonal echoes -- a phenomenon commonly known as a "picket fence effect." Lubman likens the effect to a rainbow. "An optical diffraction grating transforms white light, spreading its frequencies over space," he explains. "An acoustical diffraction grating transforms white noise by spreading its frequencies over time." The chirped echo, in other words, is a rainbow of sound.
Lubman compared sound recordings of a quetzal chirping in its natural rain-forest habitat and the echo. They weren't identical, but he found striking similarities in sound quality, frequency, length and harmonic structure -- striking enough to convince him that the echo was intentionally designed to mimic the quetzal's call.
His discovery sparked considerable excitement and controversy, especially among archaeologists. Other examples of tonal echoes can be found in classical architecture, such as the ancient amphitheater at Epidaurus, in Greece. But these are largely believed to be the result of design defects. Lubman's theory of deliberate design implies that the essentially Stone Age Mayan people possessed a grasp of engineering and acoustical principles far beyond what archaeologists thought possible. If Lubman's theory proves correct, the pyramid at Chichen Itza would be the world's first and oldest sound recording, and the Maya the earliest known inventors of the soundscape -- a concept only recently employed by modern urban artists to create sonic architecture, such as sound parks.
Few doubt that the quetzal held a place of honor in Mayan culture. Mayan priests are believed to have performed their theatrical ceremonies draped in quetzal feathers, accentuating their larger-than-life appearance. Following the Spanish conquest of Central America, the quetzal became a symbol of freedom for the indigenous people of the region, since it was believed that the bird could not long survive in captivity. Although near extinction today, the quetzal is the national bird of Guatemala and the name of its primary unit of currency. And in what some call a critical piece of circumstantial evidence, a Mayan glyph from the Dresden Codex depicts the serpent god Kukulkan with a giant quetzal behind him.
Lubman sees further proof in the pyramid's famous "shadow show." The temple is aligned astronomically so that during the spring and fall equinox, an undulating serpentine shadow projects against the balustrades of the north side of the staircase. "The quetzal sound could have been evoked by a priestly handclap made at a critical moment in the ceremony," Lubman says. "This would reinforce the dramatic impact and religious purpose."
But does it all add up to intentional design? Samuel Edgerton, an architectural historian at Williams College in Massachusetts, has his doubts. "It's an interesting theory and there's a certain validity to it," he says, citing instances where the Maya are known to have used architecture to denote spiritual symbolism. It is also clear that, in an age without electronic amplification, the Maya designed their buildings with acoustical concerns in mind. "But it's limited, as far as we know, to human sounds. To have it replicate the call of a bird is getting to be a stretch." He believes Lubman may be overstating the relevance of the quetzal to the temple at Chichen Itza. "The quetzal bird had a semi-sacredness to the Maya, but more for its colorful feathers," he says. "There's no solid evidence that it was ever worshiped or transmogrified into a god or deity."
Those native to the region seem less skeptical. While visiting ceremonial centers in Mexico, Chilean archaeologist and ethnomusicologist Claudio Mercado was told by locals that the echo effect is known locally as "la cola del quetzal," or "the quetzal's tail." His colleague, Jose Perez de Arce, a specialist in pre-Columbian musical instruments, heard similar reports while visiting the same regions, lending further credence to Lubman's theory. But George Izenour, a fellow acoustical archaeologist who specializes in the acoustics of Western classical structures, shares the archaeological community's skepticism: "It's all nonsense, but it's charming nonsense."
Edgerton and Lubman agree on one point: The Maya would most likely have discovered such effects by accident, developing their unique acoustical architecture by trial and error over time. "There's no evidence whatsoever in the history of architecture, until the middle of the 16th century A.D., where any builder made drawings to scale on paper a priori and then constructed it afterwards," says Edgerton. "Not that the Maya couldn't have done that; they just didn't." He believes the same is true of the serpentine shadow at Chichen Itza, even though academia's most famous Mayanist, the late Linda Schele, believed the Maya deliberately planned the stunning effect. "It's so unique and so remarkable that the debate is understandable," Edgerton says. "But I have to defend what I know about ancient architecture."
Edgerton admits he would find the theory more convincing if there were more than one instance of such an effect in Mayan architecture. No problem, says Lubman, pointing to similar phenomena reported at the Mayan pyramid at Tikal in Guatemala, and at the Pyramid of the Magicians in Uxmals, Mexico. In fact, one could expect to hear such echoes from any Mayan temple with a stone staircase facing an open plaza. "It's much easier to find reports of these echoes than it is to get archaeologists to investigate them," he says.
Nor are the unusual acoustical effects at Mayan sites limited to tonal echoes. Guides in Tulum on the Yucatan coast will report that the temple there emits a clear, long-range whistle when the wind direction and velocity are just right -- a possible signal to warn of developing storms. Then there are Chichen Itza's "musical phalluses": a set of artillery-shell-shaped stones that produce clear, nearly melodic tones when tapped with a wooden mallet.
"Echo chambers" similar to the Great Ball Court can be found in many European domed cathedrals -- most notably St. Paul's in London and St. Peter's in Rome -- and the large theater near Syracuse in Sicily, known as the "Ear of Dionysus." In each case, the amplification is created by sound waves echoing off the curved surfaces of the dome. But the Great Ball Court has no vaulted ceiling to provide the requisite curved surface for the reflections, and although theories abound, the source of its amplification is still not fully understood. The famed conductor Leopold Stowkowski of the Philadelphia Symphony Orchestra spent four days at the site in 1931, determined to uncover the ingenious design principles behind the effect, hoping to adapt them to an open-air concert theater he was designing. He left empty-handed.
Questions of intent aside, Edgerton recognizes the benefits archaeology could gain from acoustical expertise. Still, he urges a cautious collaboration. "Let us reconstruct from what we know, rather than conjecturing about birds."
The rest of the archaeological community seems to be slowly coming around: Lubman recently presented his first paper at an archaeology meeting, the first non-archaeologist to do so, albeit with traditional "crackpot" placement: dead last in a contributed session. But the response was cautiously positive and he's been asked to contribute an article to a prominent Mayan journal on the topic. Acousticians are responding in kind. Next month's meeting of the Acoustical Society of America will feature an entire session devoted to the work of acoustical archaeologists.
To Lubman, the fledgling field of acoustical archaeology can only augment traditional archaeology's long list of accomplishments in rediscovering our human past. And he remains convinced of his theory about Chichen Itza's chirped echo. "It's ironic that an entity as ephemeral as sound can persist longer than the creators of the space," he says. "Where else in the world have an ancient people preserved a sacred sound by coding it into stone, so that a thousand years later, people might hear it and wonder?"