Centuries before the first speakers and subwoofers, ancient Americans—intentionally or not—may have been turning buildings into giant sound amplifiers and distorters to enthrall or disorient audiences, archaeologists say.
Temples at the ancient Maya city of Palenque (map) in central Mexico, for example, might have formed a kind of "unplugged" public-address system, projecting sound across great distances, according to a team led by archaeologist Francisca Zalaquett of the Universidad Nacional Autónoma de México. (See an interactive map of the Maya civilization.)
Zalaquett's team recently discovered that Palenque's Northern Group of public squares and temples—built around roughly A.D. 600—is especially good at projecting the human voice as well as sounds like those that would have been made by musical instruments found at the site.
The Maya built many types of musical instruments, including rattling gourds filled with seeds or stones, turtle shells played with deer antlers, as well as whistles, ocarinas, modified seashells, and other wind instruments, said Zalaquett, who presented the Palenque findings at a recent meeting of the Acoustical Society of America in Cancún, Mexico.
Performers and priests may have stood atop these temples or in specialized projection rooms, which still exist, to broadcast songs and chants throughout the squares. The Maya are known to have to held public rites to commemorate enthronements, births of nobles, and war victories as well as to honor deities, Zalaquett said.
The "amplifiers" would have been the buildings themselves, and their acoustics may have even been purposely enhanced by the strategic application of stucco coatings, Zalaquett's findings suggest. Measurements at some of the buildings still bearing stucco suggest it may have changed the absorption and reflection of sounds.
"We think there was an intentionality of the builders to use and modify its architecture for acoustic purposes," Zalaquett said in an email.
Using modern sound-measuring instruments and a 3-D computer model of the site, the team concluded that sounds made atop a Northern Group temple can be heard clearly for at least the length of a football field (about a hundred yards or meters).
(Get the full story of the rise and fall of the Maya in National Geographic magazine.)
The Maya apparently weren't the only ancient Americans to use architecture to manipulate sound, another research team suggests.
In the Peruvian Andes, for instance, a stony underground maze may have been designed not only to amplify sound but to disorient minds.
Beneath Chavín de Huántar (map), a 3,000-year old ceremonial center that predates the Inca, lies a roughly half-mile-long (one-kilometer-long) complex of underground rooms and twisty corridors, all connected by air ducts.
(See pictures of Chavín de Huántar.)
While excavating the so-called Gallery of the Labyrinths (see computer reconstruction), researchers noticed that the galleries played strange acoustic tricks with the human voice and with sounds made by instruments discovered at Chavín, including marine-shell trumpets that create an animal-like roar when blown.
"If you walk and talk in the galleries, you hear your voice changing as you go through," said archaeologist John Rick, who also presented his team's findings at the acoustics meeting.
"You don't have to do a research project to know something strange is going on," said Rick, of Stanford University.
For example, some rooms and their interconnected spaces multiply echoes and bounce them back at listeners so rapidly that sounds appear to emanate from every direction at once, Rick's team found.
"The sound reflects very rapidly from all the different surfaces of the stone, which is very irregular," said team member Miriam Kolar, a researcher at Stanford University's Center for Computer Research and Acoustics.
The effect, as well as the complicated floor plan, can be so disconcerting and disorienting that the team speculates the labyrinth was intentionally designed to confuse people inside.
Psychoactive drugs may also have been used to heighten the effect, based on evidence at Chavín. For example, stone sculptures seem to show people in the maze transforming into animal-like deities with the aid of drugs.
And based on depictions found on artifacts at the site, the team thinks the inhabitants used the psychoactive San Pedro cactus. The plant, native to the region, is still used locally in shamanistic rituals, Rick said. (See a picture of an Andean artifact depicting a healer with a San Pedro cactus.)
Grinding stones and tubes of bone found at the site may also have been used to create drugs, he added. The team thinks the latter could have been used to snuff up powdered doses.
Based on these and other clues at the site, the team thinks the maze was used to as part of an initiation rite into the Chavín religion.
"The elite people from all over the central Andes would have come to Chavín to obtain the symbols and the validation that entering the cult of Chavín would allow," Rick said.
In an effort to recreate the auditory effects at Chavín as realistically as possible, the team has created detailed 3-D computer acoustic models of the maze.
"Because there aren't records that can tell us what people did in these spaces, we hope to [use the models] to perform experiments," Stanford's Kolar said.
For example, "if 50 people were in the labyrinth of galleries all singing, what would the effect be? And how loud could that get? We can test all of these questions in our models."
Archaeologist Chris Scarre, said the idea of the Maya and other ancient cultures creating acoustic effects using architecture isn't surprising. After all, temples and plazas were often "stage sets" for vast ceremonies.
"That's the kind of world in which these things are happening," said Scarre, of the University of Durham in the U.K., who wasn't involved in either of the acoustic-archaeology projects.
"In that kind of context, if you can create a mysterious sound that seems otherworldly, you've created something that is a very powerful and intriguing element in the ceremony."
It's unknown whether the builders of Palenque and Chavín intentionally designed the sites with auditory effects in mind. But maybe it doesn't matter, Scarre said. Ancient peoples, he reasoned, didn't have to understand how an effect was created to exploit it.
"Perhaps they started building structures that were designed in traditional ways," he said, "and then accidentally produced these effects."