The Sound Book: The Science of the Sonic Wonders of the World

by Trevor Cox

  From a Western viewpoint, the story seems simple. We find dissonant sounds unpleasant because the bias is “hardwired” into the brain, and this preference underpins music compositions. But in recent times, some scientists have pointed out that many cultures actually embrace dissonance. I once interviewed Dessislava Stefanova, leader of the London Bulgarian Choir, for a BBC radio program. She and a colleague demonstrated the technique of “ringing like bells.” They sang two notes that set up the strongest dissonance I have ever heard. Analysis of the sound shows that the notes occupy the same critical band of the inner ear, with a frequency spacing to maximize dissonance. But instead of resolving this dissonance to consonance, the singers just left it hanging in the air. They were enjoying the dissonance and felt no need to resolve it.

  Weighing the current evidence, I believe humans initially find consonance pleasant and dissonance unpleasant, but this innate preference can be changed by music that we hear during our lives, starting with what we hear in the womb during the third trimester. This raises the question of why we find consonance pleasant to start with. What evolutionary drivers might cause this preference? Although news articles frequently ascribe human characteristics to evolution, peering back through the ages with any scientific certainty is usually impossible. But this impediment has not prevented us from speculating. One theory is that the response is a by-product of the auditory system’s being trained to understand speech in noisy places.7 After all, there is a close relationship between speaking and singing, with the vowel sounds being virtually sung during talking. This theory could also fit with the view of experimental psychologist Steven Pinker. He famously described music as “auditory cheesecake,” something that is pleasurable but has no adaptive function, coming as a by-product of other evolutionary pressures, like learning language.

  I find it hard to believe that music serves no evolutionary purpose. Charles Darwin thought music was a sexual display, an equivalent of the elaborate courtship calls of animals such as the superb lyrebird of Australia. The male lyrebird builds a stage in the rainforest from which he pours out the most remarkable song that is an amalgamation of things he has heard. He impersonates the calls of about twenty other species, including whipbirds and kookaburras, and even mimics the sounds of camera shutters, car alarms, and foresters’ chainsaws. But while music is often about love and sex, it goes way beyond that to an abstract art dissociated from reproduction. When I went to the performance of John Cage’s 4′33″, I got a strong sense of a collective endeavor with the rest of the audience. Robin Dunbar at the University of Oxford argues that music making plays an important role in social bonding, and the ability of humans to work collaboratively is one of our reasons for evolutionary success.8 Music also plays an important role in developing bonds between parents and babies, from soothing lullabies to the exaggerated intonation in motherese (baby talk), which helps babies learn to speak a language.

  Whatever the origins of our love of music, it is known to have a strong effect on us. It activates more of the brain than any other known stimulus. Music we like excites the reward centers that release the chemical messenger dopamine. A similar response is seen with other pleasurable activities, like sex, eating, and drugs. Did my brain respond in this way to the bongs of Big Ben? Neuroscientists have yet to study in detail our response to bell sounds and other soundmarks. But given our emotional relationship to natural sounds and other familiar noises, I would expect there to be a neurochemical relationship between soundmarks and pleasure, even for the mildly dissonant warble of Big Ben.

  Important and powerful institutions, such as town halls, churches, and monasteries, use bells to signal time, to herald the start of religious services, and to mark important historical events. Bells might be rung to warn communities of danger, call men to arms, celebrate military victories, or honor the passage of lives through christenings, marriages, and funerals. Alain Corbin, who studied the role of bells in rural France in the nineteenth century, makes persuasive arguments that the sonic footprint demarcated a local community’s territory both socially and administratively. Bells were used to mark the end of the workday, so townsfolk had to stay within earshot.9

  While church bells are heard worldwide, they are usually just chimed, where the mouth of the bell hangs downward and the clapper bounces back and forth inside. Bell ringers use a different set-up to create the quintessentially English sound known as change ringing, which originated in the sixteenth century and can be heard every weekend at churches throughout the country. Change ringing produces peals of sound in rhythmic patterns from a set of bells, like an ancestor of minimalist compositions by Steve Reich or Philip Glass.

  I have always wanted to know more about change ringing, so one autumn afternoon a couple of months before my trip to Big Ben, I headed down to a church close to my home. St. James’ is a Gothic-style village church serving one of Manchester’s leafier suburbs. Ignoring the jam-and-cake stall outside the front door, and the exhibition on weddings in the nave, I climbed up an extremely tight spiral staircase, ducked under a very low doorway, and entered the ringing room. Hanging through holes in the ceiling were six thick ropes, each with its own woollen grip, or “sally.” Paul, one of the regular bell ringers, eruditely explained the practice of change ringing. Another of the regular ringers, an enthusiastic fellow named John, had a tabletop model that he demonstrated to me. I could also see what was happening above in the belfry via a webcam.

  Each rope connects to a bronze bell in the belfry through a hole in the ceiling. Although the six bells in St. James’ form the first notes of a major musical scale, melodies are not the goal. A team of half a dozen campanologists pull the ropes and ring the bells in different orders following a mathematical pattern. Opposite Paul was a whiteboard covered in bewildering grids of colored numbers connected by lines, showing examples of the order in which the bells were to be rung. As Paul explained, ringing the bells is a disciplined and regimented process with, “ears open, eyes wide on the white board.”10

  John and Paul can precisely control when a bell tolls because it is mounted on a large wheel that allows it to rotate a full circle. Before ringing, John used his rope to turn the bell upside down so that the opening pointed upward. There it waited until he pulled the rope again, tipping the bell over; it then turned a full circle before finishing pointing upward again. Another tug on the rope then turned the bell in the other direction for a full rotation in reverse. The bells are incredibly heavy, and John explained to me that I had to work with it rather than fight against it. Since I had never done this before, I got to do half the job, the back stroke. John would pull the bell around once, and then I would pull it back the other way. The rope dangled down between my legs and I held the sally like a cricket bat. When John pulled the rope and created the forward rotation, the inertia of the bell pulled my arms above my head; I tried to pull it back but completely mistimed my effort and struggled to heave the bell around. After a few more attempts, I hit a rhythm. When the bell just starts tipping in the right direction, a long, gentle pull will bring it around full circle.

  Wanting to know more about people’s responses to peals of bells, I turned to sound artist Peter Cusack, who started exploring the general public’s response to sound in London about a decade ago. His investigative technique is deceptively simple. He just asks, “What is your favorite sound of London, and why?” As well as identifying stuff for Peter to record, the question reveals personal stories about the sounds. The Favourite Sound Project has been expanded and run by others, to involve cities around the world, including Beijing, Berlin, and Chicago.

  In London, respondents to Peter’s question often mentioned Big Ben, but not always the actual sound of the bell. People remembered the time between the strikes—the moment of anticipation before the next bong, when the auditory cortex increases activity as it directs attention waiting for the sound—something I experienced intensely in the belfry. The sound of Big Ben on the street is quite different because the i
mpact is diminished by traffic noise. When the great bell first tolled about 150 years ago, Londoners could hear it from farther away than is possible today. Iconic sounds are much more localized nowadays because of the blanket of noise in our cities.

  Cockneys are the working-class people from the East End of London famous for their rhyming slang, saying “apples and pears” to mean “stairs,” “plates of meat” for “feet,” and “trouble and strife” for “wife.” To be a true Cockney you have to be born within the sound of the bells of St. Mary-le-Bow Church. But an acoustic study implies that Cockneys could soon be “brown bread” (dead), because the area over which Bow Bells can now be heard is so small that it contains no maternity hospitals.11 A hundred and fifty years ago, London was as quiet as the countryside is nowadays, with a level thought to be 20–25 decibels in the evening, and it is estimated that the bells could have been heard up to 8 kilometers (5 miles) away. Nowadays, the noise from roads, aircraft, and air conditioners mean that the London sound level is usually about 55 decibels, and the bell tolls travel audibly across a mile at best.

  Six months before I heard Big Ben, I found myself only 500 meters (550 yards) from St. Mary-le-Bow, listening to a sound sculpture called Organ of Corti (Figure 8.8). Designed by Francis Crow and David Prior, it aimed to sculpt and recycle environmental noise such as the traffic sounds that mask the bells of London. Organ of Corti was made from ninety-five transparent, vertical acrylic cylinders, each about 20 centimeters (8 inches) in diameter and rising to a height of 4 meters (13 feet). Named after the part of the inner ear within the cochlea that responds to sound, the sculpture reminded me of a giant child’s plastic toy, with the forest of translucent cylinders distorting the bodies of people walking through.

  The sculpture’s design exploits a scientific discipline that was sparked by another artwork. Installed in Madrid in 1977, Eusebio Sempere’s Órgano is a large, circular forest of vertical steel cylinders. Not until the 1990s did measurements by Francisco Meseguer, of the Institute of Materials Science in Madrid, and his colleagues reveal that this minimalist sculpture shapes sound. Meseguer normally works on photonic crystals, tiny structures that alter light. Shine white light onto one of these crystals, and some colors become trapped inside and do not pass through to the other side. If you pick up a peacock tail feather and twist it around in your fingers, you will notice how the color changes. Microscopic periodic structures create this iridescence. In nature, the most striking colors on butterfly wings, squid bodies, and hummingbird feathers are made by photonic crystals and not pigments.

  Figure 8.8 Organ of Corti.

  A conversation with acoustics expert Jaime Llinares made Meseguer realize that if photonic structures were scaled up, they would make a sonic crystal, stopping sound at particular frequencies from passing through. In 2011, I showed that sonic crystals also reflect some frequencies intensely, mimicking the iridescence of butterfly wings (unfortunately making an unpleasant sound).12 Órgano was just the right size for Meseguer and Llinares to test out their idea, being about 4 meters (13 feet) across, with the cylinders regularly spaced about 10 centimeters (4 inches) apart.13

  Meseguer placed a loudspeaker on one side to produce noise. A microphone on the other side confirmed their hypothesis: there were band gaps, frequencies of sound that did not go through the array of cylinders. The effect is caused by interference, a phenomenon first explained by British physicist Thomas Young in 1807. Young was a child prodigy who could speak fourteen languages before he was nineteen and first trained as a physician. His classic double-slit experiment, which is still used in schools to teach physics, is illustrated in Figure 8.9. When a monochrome light is shone through two slits, a pattern of light and dark appears on a screen. In some places waves from the two slits arrive with their peaks and troughs aligned and there is constructive interference, giving a bright patch. Sometimes the two waves are misaligned and they cancel each other out, leading to a dark patch caused by destructive interference.

  Figure 8.9 Thomas Young’s double-slit experiment.

  The same effect can be demonstrated with sound if you use a loudspeaker and a screen with the slits farther apart. You can go further and add more slits in the screen, and even many perforated screens spaced out one in front of the other. If you then remove the screens and place a cylinder where each slit was, you have made yourself a sonic crystal like Eusebio Sempere’s sculpture. As in the double-slit experiment, what is heard passing through the forest of cylinders is determined by constructive and destructive interference, with sound of some frequencies getting trapped inside, rattling back and forth between cylinders and failing to emerge.

  As soon as people discovered that sonic crystals block sound, experimenters began testing their use as noise barriers. But crystals attenuate only a few select frequencies. Consequently, solid barriers made of wood and concrete are nearly always more effective at stopping broadband noise. A colleague of mine at Salford, Olga Umnova, has been experimenting with an acoustic black hole that absorbs a wider range of frequencies. The black hole is made by gradually decreasing the diameter of the cylinders at the edge of an array of crystals. The result is an outer shell that guides the sound to the core, where it can be removed using conventional absorbants.14 Sonic crystals have also caught the media’s attention as a way of making the sound equivalent of Harry Potter’s cloak of invisibility. Normally, we can sense the presence of an object by hearing the sound reflecting from it. The “cloak of inaudibility” surrounds the object, gracefully bending acoustic waves around it so that it cannot be heard. Unfortunately, sonic crystals are often too big to be practical, because sound waves are quite large, especially compared to light.

  Organ of Corti had some of its acrylic cylinders missing to form a sinuous path through the middle of the sculpture. Being a regular array of cylinders, the artwork should have amplified certain sound frequencies and attenuated others. But I had chosen a bad day for listening in London. Workers were digging up the road using jackhammers, and as I tried to listen for subtle changes in the noise, the power tools stopped and started randomly, making it impossible to tell what the sonic crystal was doing.

  Later that summer the sculpture was placed near a weir on the River Severn in England. The more constant noise from the waterfall made it easier to hear the sound being sculpted. Francis Crow told me that the effects were most obvious as you exited the sculpture. Walking into the structure, the forest of cylinders subtly removed selected frequencies from the noise, but such absences could be hard to hear. Walk out of the artwork and these removed frequencies reappeared and could be heard. This makes sense, because our ears are designed as an early warning system to listen for new sounds, not subtle absences.

  Francis explained to me that some of the motivation behind the work was to change how people listen: “It’s hearing what’s already there but framed through the structure.”15 It was the sonic equivalent of Skyspace, a series of works by James Turrell. These are large rooms where visitors view the sky through an aperture in the ceiling, framing light and space. Organ of Corti was framing how we listen to sound. Appreciating the work takes time; near the weir, people tended to linger and enter a meditative state. One visitor took this idea to an extreme and spent over half an hour inside the sculpture, commenting, “I made my own symphony.” Another described the subtle ebb and flow inside as “disorienting.” It is difficult to experience sound art quickly. A brief glance at a piece of visual public art is likely to yield more than a brief encounter with a sonic artwork.

  Many minimalist sculptures distort sounds. Several of Anish Kapoor’s artworks are large, concave light mirrors. I went to see Her Blood (1998) at the Manchester Art Gallery in England. The work is made from three huge, concave dishes 3.5 meters (11 feet) in diameter propped vertically against the gallery walls. Two were highly polished mirrors; the third was stained deep red. As visitors walked toward a dish, the visual reflection of their figure was distorted. Some distance away, they could see thems
elves smeared across the lower half of the dish; as they walked closer, suddenly their image formed rings going completely around the dish. At this position they were at the focal point for both light and sound. Attendants had noticed the way the reflection distorted voices, and they were encouraging visitors to speak at the dishes.

  The concave dishes of Her Blood did not behave much differently than the radome in Teufelsberg. In contrast, Richard Serra’s giant works at the Guggenheim Museum in Bilbao, Spain, produced an astonishing diversity of sounds. It was like having a giant sound-effects unit to play with. The Matter of Time (2005) is an installation of seven giant sculptures made from spirals, serpentine ribbons, and sinuous curves of rusting steel that rise many yards overhead. The brown metal walls rise at angles, forming narrow passages that twist and turn, sometimes closing over in an inverted V, disorienting a sense of space and balance as you walk through. It is like being in a giant steel maze; around the corners I expected to bump into Alice from Wonderland.

  When I visited, the gallery echoed with the hubbub of chattering schoolchildren. As I entered some of the works, I could hear the effects of going into a partial enclosure: the ambient noise quieted, and my ears sensed the quick reflections from the steel walls. The sound was being reframed as happened with Organ of Corti.