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

by Trevor Cox

  I was fortunate to have a press pass, which meant I could take out my digital recorder, wait for a moment when I would not disturb others, and clap my hands to reveal the acoustic. In the middle of the giant spirals were large, round arenas about 8 meters (30 feet) across. In these spaces the reflections focused into the middle. This focusing created Gatling gun echoes, as the claps whizzed past me every twenty milliseconds. In some places, stamping my feet made repeated twangs like vibrations propagating up and down a very long spring. As I mentioned in Chapter 5, some were very good whispering galleries, carrying my voice efficiently from one end to the other, with the sound hugging the walls of steel.

  Best of all was Snake, a work made from three long, tall, twisting metal sheets forming two narrow corridors about 30 meters (100 feet) long. The passageways were only about a meter wide, and resonances across the narrow width colored my voice. When I stood in just the right place, with a flat bit of the ceiling high above the sculpture, the sound would ricochet back and forth between the ceiling and the floor. Sound would also go along the narrow channel and be reflected from other sculptures at the end, before being returned as a diffuse echo. Stamping my feet on the floor was very satisfying because in just the right place I could impersonate a rifle shot. I was not the only person enjoying the acoustic distortions; others were calling “hola,” “echo,” and “boo” as they walked around.

  When Peter Cusack asked Londoners about their favorite sounds, often the answers were about mundane and everyday sounds. The favorite-sound question is personal, so the semantic meaning of what is heard usually trumps the raw physical characteristics of the acoustic wave. If you take a moment’s break from reading and just listen, what do you hear? I can hear voices from the office next door, rain falling on the pavement outside, and footsteps in the corridor. Did you also come up with a list of what made the sounds? I thought “voices, rain, and footsteps,” not “mumbling, pitter-patter, and tap tap.” We describe what we hear mostly in terms of sources and metaphorical meanings, not their intrinsic sound.

  But sometimes the physical characteristics of what we hear do matter. Something loud like an explosion triggers a rapid fight-or-flight response. A plane flying overhead might not be as loud as an explosion, but the sheer volume of the noise might still drown out a conversation. A melody is just a sequence of abstract tones, yet it can tap deeply into our emotions, evoking joy, sorrow, and love. But mostly, for everyday sounds, it is the cause of what we hear that matters. Where possible, the brain identifies the source, and our response is then colored by how we feel about what caused the sound. If you hear a bus in a city square, your response is likely to be strongly influenced by whether you want to get on it, or by your attitude toward public transport: are buses a waste of taxpayers’ money clogging up the road or a public good easing pollution and congestion?

  This is why Peter’s question about sonic favorites reveals sounds that, at face value, have little aesthetic appeal: the announcement “Mind the gap!” in the London Underground, the siren of a New York Police Department squad car, or Turkish market stall holders shouting out offers on Turmstrasse in Berlin.

  I am struck by the similarity between the favorite-sound answers and what correspondents told Andrew Whitehouse about birdsong. Many of the stories about city sounds and birdsong are not about the awe-inspiring, surprising, or most beautiful. They are not the sonic equivalent of the Taj Mahal, the Golden Gate Bridge, or the Grand Canyon; instead they are about the sounds that remind us of special places and times, or the sounds likely to be heard in our everyday lives. People often mentioned transportation sounds. After all, getting around a city is such an important part of living and working there. Imagine if the study had asked for favorite images of London; respondents would probably have listed visually appealing or striking attractions such as St. Paul’s Cathedral, the London Eye, or Tower Bridge. The ringing of Big Ben is an exception, a sound that has both aesthetic beauty and deep historical, personal, and social meaning for the British.

  Peter has been running the Favourite Sound Project for over a decade, so some of the original sounds have disappeared. When trains used to arrive in London, there was a staccato cascade of door slams as passengers disembarked. This sound disappeared as the old rolling stock was decommissioned. What replaces these distinctive sounds is similar across the world because of globalization of technologies and products. Regretfully, cities are becoming more sonically similar and less individual, mimicking the visual homogenization of main street.

  Andrew Whitehouse found that birdsong heightened some emigrants’ sense of being in an alien country. I got a similar feeling when I traveled to Hong Kong, but with a different sound. My strongest sonic memory was the hubbub of the massed crowds of Filipino women along walkways and crowded into shopping malls. Under the HSBC tower block is a large, covered plaza, which was alive with the high-pitched chatter of females socializing. To Hong Kong residents this is a common sound, as domestic workers gather on Sundays around the city center, lay out their picnic blankets, and socialize with friends. But to me as an outsider, it stood out as something special and unique in Hong Kong.

  Under the tower block, the semi-enclosed space amplified the chatter of the women, enhancing the effect. Indeed, soundmarks can be created by the concrete, brick, and stone of the city because they form spaces that alter sound in surprising ways. The Greenwich foot tunnel from Chapter 4 appeared in the list of London’s favorite sounds because of the way it distorts voices and footsteps.

  When I heard about Italian artist Davide Tidoni, I realized I had found a sonic soul mate, in that he explores the hidden sound effects in urban landscapes. In one of Davide’s projects, he bursts balloons and brings spaces to life. A short, loud, impulsive bang is ideal for revealing sonic features. I was fortunate to see him; he had the free time to visit me because he had been forced to take a day off from working in London. Security guards were objecting to his bursting balloons and recording around the Barbican in London.

  I decided to take Davide on a walk around the canals of Manchester to sample the acoustics of nooks, crannies, and arches first formed during the Industrial Revolution. After lunch we stopped at a shop to buy some balloons before walking to the towpath of the Rochdale Canal. Fully opened in 1804, this was the first canal to cut across the Pennines, the ridge of mountains that separate eastern and western England in the north. Under a dingy, low, arched bridge I placed my digital recorder on the floor, narrowly missing a discarded condom. Davide then inflated a yellow novelty balloon into the shape of a long, bulbous worm with a couple of tentacles sticking out the top. He waited patiently with a pin poised until the thundering cars driving over the bridge quieted. A series of ricocheting twangs followed the sudden bang as the worm burst and the sound bounced around underneath the arch.16

  We had spent a long time over lunch discussing the merit of different types of balloons—hence this attempt with the novelty worm. But after the first test, we reverted to using conventional round shapes, preferring the way their shorter, sharper bangs revealed the acoustics more starkly. Davide explained to me that his sonic exploration is about building a relationship with the spaces he is in. He also told me, “What is striking is to see how apparently the same gesture and sound are perceived in different subjective ways depending on the position of the listener and his emotional state.”17

  Davide uses balloon bursts to raise people’s awareness of spaces and train their sensitivity to sound. Videos of these walks show people initially being alarmed by the loud bang and wincing—even the person who is plunging the pin into the balloon and therefore knows the explosion is coming. Then people smile, giggle, or stare in disbelief as strange tones and echoes are produced; Davide sees these reactions as a “need to externalize the emotions.” On one video a young woman calls out, “Bellissimo!” as she looks up and tries to work out where the sound is coming from. These responses give insight into our hearing. Initially there is a startle response, an uncons
cious reflex that occurs to prevent injury. People blink to protect their eyes and tense their muscles to brace themselves in case they are about to be physically struck. This reflex is incredibly rapid, going through a very short neural pathway in just 10–150 milliseconds. The slower secondary responses, such as the giggling, occur once the brain has had a chance to properly access the situation and realize that there is no real danger.

  Davide has the following wonderful idea of an acoustic gift: “I usually send an invitation to someone that I feel very close to and then we listen together to a place that is particularly meaningful to me.” I am not especially close to Davide, but our journey around Manchester was focused on reaching one place, which, I guess, I gave to him as a gift. Built in 1765, Castlefield Wharf is at the end of the Bridgewater Canal. The waterway is commonly cited as the first canal built in England, designed to transport coal to Manchester at the start of the Industrial Revolution. A nineteenth-century railway bridge spans the canal basin, forming a tall, narrow archway where the sound reverberates for a ridiculously long time. We stood under this brick arch clapping and shouting, bewildered by the lingering sound. This narrow space has a reverberation time much longer than a classical concert hall.

  Though celebrated by many, the ringing of bells is also a common cause of noise complaints. One case involved the Church of All Saints in the village of Wrington, England. Built in the late fifteenth century, the church has a square tower housing a peal of ten bells. It had marked every quarter of an hour day and night for a century, but in spring 2012 the bells fell silent after local government officers declared them to be a statutory noise nuisance. Fortunately, a compromise was reached whereby the clock chimes only hourly overnight.18

  Sound artworks have to be carefully located to prevent similar complaints. I discussed this question with Angus Carlyle, an expert in sonic-arts practice at University of the Arts London. He suggested, “We seem very tolerant of very visible ugliness in the built environment. We also tolerate a mixing and mashing together of visual style in architecture . . . But my hunch is that there would be much less sympathy for an equivalent density of creative sound interventions.”19

  Retired academic Tony Gibbs made a similar point when I phoned him. I called Tony because he has written one of the few academic books on sound art. He argued that the sonic equivalent of large public artworks would have to make a similarly bold acoustic statement—in other words, make lots of noise. As Tony explained, “We as a public, as a culture, don’t like massive noises . . . to persuade people that they should regard noise as art is a big ask.”20 For a monumental piece of visual art, such as the 120-meter-high (400-foot) narrow Spire of Dublin, if people don’t like its appearance they can simply look away. Screening out sound art would involve reaching for earplugs.

  It is a shame that there are relatively few public sound artworks, because some of the most iconic images in the world are sculptures: the Statue of Liberty in New York, the Great Sphinx guarding the pyramids in Egypt, and Christ the Redeemer towering above Rio de Janeiro. In recent decades, governments have turned to public art as a way of bringing communities together, attracting tourism, and aiding or symbolizing regeneration. Striking works have resulted, like Antony Gormley’s Angel of the North. With a wingspan wider than that of a jumbo jet, this giant, rusting figure towers over Gateshead in England. Is it possible for artists to create the sonic equivalent of this giant work—permanent public sound art that comes to define a place? Something that would rival Big Ben for its iconic sound? Angus Carlyle saw no reason why sound art could not create an “iconic rapport between place and the heard,” however, he felt that sound art was too much in its infancy and would have to establish greater prestige before it could attract permanent commissions.21

  Would public sound art be more accepted if, instead of a loud noise, it produced something more tuneful? Just outside the city of Lancaster in California is a soundmark that creates a rendition of Rossini’s “William Tell Overture.” Strangely, no electronics are involved. This is a musical road. It creates the melody from wheel vibrations. It is a bit like a rumble strip, the line of ridges off the side of a major road that create a buzzing sound alerting drivers to danger. The musical road uses grooves cut in the asphalt rather than the bumps you get in rumble strips, but the sound is made in a very similar way. The pitch of the notes depends on how fast you’re driving and the spacing between the grooves, with close spacing giving a high note, while corrugations spaced farther apart lower the frequency. The road near Lancaster takes the rumble strip one step further by changing the spacing between the grooves in a pattern to create a tune.22

  The corrugations were first cut for a car ad, possibly inspired by the dozen or so musical roads that exist in Korea and Japan, or the Asphaltophone, which was created by Danish artists back in the 1990s. I decided to visit Lancaster to hear the musical road for myself.

  It was on a Saturday in June, six months after popping balloons in Manchester, that I turned west off Route 14 onto Avenue G. This is a flat, featureless road a few miles out of the city. After a short distance, a white road sign near a line of trees announced, “Musical Road Presented by City of Lancaster. This Lane .” As my tires rolled over the first few notes, I smiled at this magnificently silly creation. Every time a tire hits a groove in the road, a short sharp vibration travels through the tire, into the suspension, and then into the body of the car. Inside, you hear the sound radiated by vibrations of the cabin interior. The road plays eight bars from the “William Tell Overture.” The “March of the Swiss Soldiers” is a frantic gallop, and the road plays the first phrase from the main melody.

  I swung the car around and headed back to have another go. Over the next hour, I drove over the grooves half a dozen times trying my microphone in different places. I got the best recording from inside the glove compartment. In this location, the microphone was close to vibrating bits of the interior trim that made the tune louder, while being sealed away from the high-frequency wind noise created as the car cut through the air. Cruise control was useful to set a steady pace, ensuring that the tune did not speed up or slow down as I drove over the road.

  As the tire and bodywork of the car are vibrating, they radiate sound outside the car as well as inside. Even with a normal, ungrooved road, tires make noise as they roll over the pavement, and considerable research effort goes into reducing this sound. When I stood on the shoulder, I could clearly hear the melody from passing cars, with the added pleasure of seeing the smiles on the drivers’ faces and hearing the pitch of the notes slide about. I stood where the grooves of the first note started, and as a car started the tune and disappeared into the distance, it was as if the first note was sighing as the pitch dropped by three semitones. This is the Doppler effect, which is commonly heard with police sirens and fast-moving trains. As the cars drove away from me on the musical road, the sound waves stretched out and the frequency dropped. I would have liked to make more recordings, especially when two cars at different speeds were playing the road, because the result was a clash of renditions at unequal pitches. However, it was so windy that it was difficult to stand up, and the gale blowing across the microphone created too much noise for decent recordings.

  Figure 8.10 Grooves in a musical road.

  I have replayed the musical road to lots of people, and many struggle to recognize the tune, even though it is a very famous piece of classical music and was the theme music for The Lone Ranger. The problem is the tuning of the notes, with most being at the wrong frequency. As physicist David Simmons-Duffin explains in a humorous blog post, the designers mucked up the tuning because they got the spacing of the grooves wrong.23 For the lowest note, which starts the tune, the distance between the front edges of adjacent grooves averaged out at about 12 centimeters (4¾ inches), as illustrated in Figure 8.10.24

  Down the road thirty-six notes later, the tune reaches its high point, with a note that should be an octave above the first. An octave is a doubling in freq
uency, so the car tire needs to hit the grooves twice as often, which means the distance should be halved to 6 centimeters (2⅜ inches). But on the road the spacing is actually 8 centimeters (3⅛ inches). This means that, instead of an octave, the musical interval is closer to what musicians call a perfect fifth. When you are taught musical intervals, you learn to associate them with particular tunes. So instead of hearing the big leap from the first two notes of “Somewhere over the Rainbow,” drivers hear something like the first two notes of the theme music for the film Chariots of Fire.

  If the interval had been exactly a perfect fifth, then the tune would have simply been disappointingly wrong, but the melody was excruciating to listen to because the sound’s frequency was between musical notes, so the road was out of tune.25 Forcing notes to be at particular intervals and disallowing sounds with frequencies between is vital for most music. In theory, an instrument like a trombone with its sliding valve can produce any frequency within its playing range. But such a free-for-all is unlikely to produce beautiful music. The octave interval is found in nearly all musical cultures.26 A doubling in frequency is readily processed by the human brain because two notes separated by an octave share the same neurological pathway. This is also true for some other animals. Rhesus monkeys can be trained to recognize simple strong melodies that are transposed by an octave, such as “Happy Birthday to You.”27

  The octave is then subdivided into more notes. In Western music, octaves are divided into twelve smaller intervals called semitones, with melodies usually using a subset of these that make up a musical scale. But in Asian music such as gamelan, things are different. The sléndro scale divides the octave into five notes and creates a sound similar to playing just the black keys on a piano; the pélog scale uses seven uneven intervals. Therefore, the notes found in melodies are not just about some innate processing in the brain; it also comes down to what you have learned by listening. The musical road may have produced frequencies that did not match any notes I know of, but maybe there is a culture where it is perfectly in tune.