The Sound Book: The Science of the Sonic Wonders of the World (10 page)

David Lubman, however, says it's “hard to believe it wasn't intentional, hard to believe it wasn't noticed.”
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And he goes further, explaining that the acoustic phenomenon is connected to the light shadows that are cast on particular days. At the equinoxes, a zigzag shape appears down the side of the staircase—a distinctive shadow forming a tail for the serpent statues at the bottom of the stairs. His explanation is that around the spring equinox, the quetzal bird undertakes a spectacular diving display, and it looks like a flying serpent. At the bottom of the staircase is the head of the serpent, at the exact point you need to clap to make a chirp. So the echo helps explain the visual display.

I think there are three possible scenarios. First, the Mayans deliberately built their pyramids to make serpent shadows and chirping staircases. Second, it was not deliberate design, but the Mayans noticed that their pyramids chirped and then incorporated the sound into ceremonies. Third, and least romantic, modern guides noticed the chirp and made up this tall tale to entertain tourists.

Unpacking which of the three scenarios is correct is difficult. It is like examining the orientation of ancient structures to the stars and sun. It is easy to prove that places are astronomically aligned in an interesting way, but proving that such alignment was deliberate is impossible.
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We can learn from modern examples where documents exist to resolve arguments. There are whispering galleries in the US, Europe, and Asia where you can hear ghostly voices apparently emerging from within the walls (more on this in Chapter 5). With so many places built that have this acoustic effect, it is tempting to assume deliberate sonic design. But most are accidents of design, and none appear to have been exploited for rituals and ceremonies—even the ones within cathedrals.

I find it hard to believe that Mayan pyramids were deliberately designed to chirp, but I am open to the idea that the sound might have been exploited in ceremonies. Whichever account of events you believe, an important thing to try at Chichén Itzá is to test the chirp and wonder whether, a thousand years ago, Mayan priests did the same, summoning the quetzal bird, a messenger from the gods.

The wind, playing upon the edifice, produced a booming tune, like the note of some gigantic one-stringed harp. No other sound came from it . . . overhead something made the black sky blacker, which had the semblance of a vast architrave uniting the pillars horizontally. They carefully entered beneath and between; the surfaces echoed their soft rustle; but they seemed to be still out of doors. The place was roofless . . . “What can it be?”
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This dramatic description of Stonehenge comes toward the tragic end of Thomas Hardy's
Tess of the d'Urbervilles
, where Hardy refers to that famous ring of stones as “a very temple of the winds.” Disappointingly, the wind-driven drone has fallen silent, probably because many stones were removed and rearranged in the twentieth century. But even without the “booming tune,” the sound of stone circles can surprise because, as Hardy observes, they can have an unexpected indoor quality.

Stonehenge is one of the most iconic prehistoric sites in the world, so naturally it has attracted curious acoustic archaeologists. There have been many suggestions for why ancient denizens built Stonehenge. Ignoring the ridiculous speculation that it might be a UFO landing site, most sensible ideas involve rituals.
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Across cultures, human rituals involve sound, whether for celebration or for mourning, so it is probably safe to assume that speech, music, and other sounds were played within stone circles.

My colleague Bruno Fazenda and musicologist Rupert Till went through a standard acoustician's ritual of bursting balloons one morning at Stonehenge just after sunrise. Bruno told me that the sunlight catching the mist and clouds cutting through the circle of stones stunned him with its beauty. But he was less impressed by the sound. When he stood in the middle and clapped his hands or burst a balloon, he could hear only a faint echo from the partial remains of the sarsen circle (the iconic uprights that are capped with horizontal stones). Unfortunately, modern-day Stonehenge is very different from its ancient counterpart, and not just because of the polluting noise from the nearby road. With many stones removed or rearranged, the modern acoustic is a poor imitation of any past sonic glories.

To go back in time to hear the past acoustic, Bruno and Rupert decided to travel nearly 8,000 kilometers (5,000 miles) because, extraordinarily, there is a full-scale replica of Stonehenge in Maryhill, Washington. Constructed by a wealthy American named Sam Hill to honor his fallen companions in World War I, the monument was completed when the altar stone was dedicated on July 4, 1918. On a trip to England, Hill had been told about possible human sacrifices at Stonehenge and had decided that a copy of the prehistoric monument would be a fitting tribute to the suffering and loss of servicemen from Klickitat County.
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Bruno and Rupert made detailed field measurements at the Maryhill monument one hot and dusty summer, annoying dog walkers and tourists with loud drumming and chirps as they tried to capture and understand the acoustic. They rose early in the morning so that they could get going before the winds had a chance to pick up and create too much buffeting noise on the microphones. Fortunately, the monument was carefully constructed as a faithful replication of one of the old layouts of Stonehenge. Still, some differences between the monument and the original Stonehenge remain: the concrete blocks at Maryhill are too perfectly square and have a finish reminiscent of a 1970s textured ceiling, whereas each Stonehenge stone has individual character from the way the stones were shaped. From my knowledge of designing acoustic reflectors for concert halls, however, I would doubt this made a vast difference to the sound within the circle.

“Maryhill is quite awesome, a beautiful architectural place on the banks of the Columbia River. It is also a valuable archaeological model, a window into the past, giving you a sense of what it would have been like standing in the original Stonehenge,” Bruno explained to me.
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He also described how his footfall on the gravel changed as he entered the circle, giving a striking, unexpected sense of being inside a room. Exactly the same feeling described by Hardy in
Tess of the d'Urbervilles
.

At first the results of the acoustic measurements surprised me. Burst a balloon at Maryhill, and the sound will ring and reverberate for over a second, a decay time more in common with a school hall than an outdoor space. Given that there is no roof and there are spaces between the stones, I naturally assumed sound would rapidly disappear up to the heavens, but actually, some sound stays bouncing around horizontally among the stones. However, the acoustic is subtler than that of a booming school hall because the reflections are quieter; you have to listen carefully to notice the difference. Nevertheless, these reflections would have been helpful during rituals. As Bruno explained, “It is a surprisingly good place for speech, because reflections reinforce your voice and you can talk to people even from behind some of the inner stones.”
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Whereas the insides of the stones at Stonehenge have been carefully and meticulously worked to make a smoother, more concave shape, the outsides are often quite rough. Pioneering acoustic archaeologists Aaron Watson and David Keating have suggested that the purpose of smoothing the stone interiors might have been to focus the sound.
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However, Bruno heard no distinct echo caused by focusing from the rings of rocks in the Maryhill monument. The outer sarsen stones might have produced a focused echo on their own, but reflections from the inner ring of stones hid whatever echo there might have been. The ear combines reflections that arrive at roughly the same time. At Maryhill, the sounds bouncing off the inner and outer stones arrive too close together to be perceived separately, rendering inaudible any possible echo.
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Bruno and Rupert had hoped to hear a whispering-gallery effect around the circle of stones, but the gaps between the stones ruin this effect. Neither did they hear bass drones or Hardy's “temple of the winds”—even when a gale was blowing through the stones in the afternoon.

T
he chance to experience an ancient resonance like the one that eluded Bruno Fazenda at Stonehenge is what drew me to the Neolithic burial mound at Wayland's Smithy. I also had a less noble motivation: a curiosity to sample a chamber that featured in an infamous academic publication. In 1994, Robert Jahn and collaborators carried out what they described as “rudimentary acoustical measurements” inside six ancient structures.
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What they found was that the chambers contained acoustic resonances.

Just like a Roman wine jug, a beer bottle contains air with a particular resonant frequency, which is why you can make a flutelike hooting sound when you blow across the top of one. More specifically, when you blow across the mouth of a bottle, a small plug of air in the neck begins vibrating back and forth against an air spring created by the rest of the vessel. Blowing across the mouth of another bottle, identical except for an elongated neck, sounds a lower-frequency note. The elongated neck means that a longer plug of air is oscillating, and because this greater quantity of air is heavier, the resonant frequency is lower.

Paul Devereux, one of Jahn's collaborators, claimed in a 2001 book that the ancient structures had specific resonant frequencies that enhanced the human voice in an intentional way.
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This assertion irked acoustic scientist and mathematician Matthew Wright, who noted that all enclosed spaces, such as bathrooms or burial chambers, have resonances—rarely as dramatic or obvious as that emanating from an empty beer bottle, but still powerful enough to fool you into thinking you are a great singer while showering. Wright composed a conference paper entitled “Is a Neolithic Burial Chamber Different from My Bathroom, Acoustically Speaking?”
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I decided to put Wright's research to the test by analyzing the balloon bursts from Wayland's Smithy and measurements I made in my bathroom (Figure 2.3). Both plots are jagged lines, with distinct peaks and troughs. The peaks represent the frequencies where there are resonances. Any singer will find notes at these frequencies sounding richer and fuller than normal. If you were to sing a note a little above 100 hertz in one of these places, you would excite a resonance that would reinforce and enrich the sound. Move up to about 150 hertz (a musical interval of a perfect fifth, the leap between the first two notes of the
Star Wars
theme), and the valleys in the graphs at that frequency show that there is no prominent resonance to reinforce your voice, so it would sound thinner. The 100-hertz resonance is conveniently located toward the bottom of my vocal range, ideally suited for impersonating Barry White singing “Can't Get Enough of Your Love, Babe” (a song slightly more appropriate in a bathroom than in a burial mound).

The peaks in the plots demonstrate how acoustically similar the bathroom and burial mound are. Burial chambers and bathrooms are similar in size, big enough to get into and lay a body down, whether for disposal of the dead or for a soak in the bath. This means they both have resonances that are in a frequency range useful for enhancing singing.
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Matthew Wright's paper concluded that it is unlikely that acoustics influenced the design of burial chambers. After my own scientific exploration, I'm afraid I agree. The cross shape of the Wayland's Smithy has no discernible affect compared to a simple box. Either kind of small room would have blessed our ancestors with resonant frequencies that would have added a booming quality to chanting and singing, if that is what they did around the decomposing bodies of their kin.

Because we listen through twenty-first-century ears, which have become accustomed to hearing reflections from and within buildings most of the time, it is easy to forget how unusual the acoustics of burial chambers and stone circles would have been to our ancient ancestors. Whatever drove the design of Stonehenge, Wayland's Smithy, and other prehistoric sites, we must rediscover our ancestors' listening skills to really understand the archaeology. And that begins with listening to animals.

Figure 2.3 Resonances in two small spaces.