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

by Trevor Cox

  Placing Sound

  I

  f I were to ask you about iconic images of London, Paris, or New York, you might name famous landmarks like the Houses of Parliament, the Eiffel Tower, or the Statue of Liberty. But what about iconic sounds? How readily can you name soundmarks, those keynote sounds that define a place and make it special? Soundmarks can be as varied as landmarks: in Vancouver, Canada, the Gastown steam clock marks time not with bells but with whistles; on the Orontes River in Hama, Syria, ancient waterwheels called norias let out loud groans as they slowly rotate, and my travels in the southwestern US were punctuated by the dissonant hoots of Amtrak trains.

  For Great Britain, the bongs of Big Ben, the giant bell housed within the clock tower of the Houses of Parliament in London, are a signature sound. In the UK, Big Ben rings in the New Year, has been broadcast at the start of news bulletins for decades, and starts the two-minute silence on Remembrance Day (Britain’s Veterans Day). What makes chimes of bells so special? The answer to this question is partially social (bells have played an important cultural role for millennia), but there is also something special about the sound itself. Listen to a bell chime, and what at first seems a simple ring is actually a very complex sound. Why does it start with a clang? Why does the ringing have a dissonant warble? What role does the anticipation of the strike play in our perception of a great bell?

  These were the questions going through my head as I approached the Houses of Parliament. Winter sunlight was glinting off the gilded ornamentation around the clock faces on the day of my audience with Big Ben. The outside of this Gothic revival tower is a grand Victorian edifice, a popular establishing shot for film directors to portray “now in London,” but the inside is utilitarian. More than 300 stone steps spiral up a narrow staircase to the belfry. The tour took a breather halfway up the tower in a small room that wraps around the staircase. There, our guide, Kate Moss (not the supermodel), told us about the amazing engineering behind the clock’s construction in the mid-nineteenth century.

  The astronomer royal at the time, Sir George Airy, had set exacting standards. The first stroke of each hour had to be accurate to within one second, and he insisted on being telegraphed twice a day so that he could check the timing. Such precision was greater than that of similar clocks of the day, and difficult to achieve because wind pushing on the 3- and 4-meter-long (10- and 13-foot) copper clock hands can change the speed of rotation. Barrister and gifted amateur clock maker Edmund Denison came up with the solution: the Grimthorpe escapement, which isolates the giant swinging pendulum in the middle of the tower from the vagaries of the weather.

  Rested, we climbed more steps before stopping in a tight corridor behind the clock faces. A clunk from the clock mechanism was a signal that the next strike of the bell was two minutes away, so we quickly climbed the final flight of steps up into the belfry. This simple, functional space, with scaffolding and wooden walkways, is completely open to the elements, and a bitingly cold wind whistled through.

  The great bell is 2.2 meters (7 feet) high and 2.7 meters (9 feet) in diameter, and it weighs 13.7 tonnes (about 15 tons). Since we were standing only a couple of yards away from the metal, Kate handed out earplugs to protect our hearing. Four bells in the corners of the belfry produce the famous Westminster Chimes before the great bell is struck. Kate instructed us to listen for the third chime bell, which would signal a good time to put in our earplugs. My anticipation and excitement built during the long pause between the Westminster Chimes on the corner bells and the bongs from Big Ben. A large, 200-kilogram (440-pound) hammer drew back slowly before crashing forward and striking the outside of the bell. Even with earplugs in, the sense of power was visceral. The sound resonated the air in my chest like a pumping bass line in a nightclub.

  With ten strikes to enjoy, I could examine the quality of the bongs in detail. At first there was a clank of metal on metal, which gradually faded into a sonorous ringing that lasted about twenty seconds. While the initial hammer blow created sound with lots of high frequencies, these rapidly died away, leaving a gentler low-frequency ring, which slowly warbled.

  The start of a musical note, the “attack,” can be a fleeting moment, but it is incredibly important. As a saxophonist, I spend a lot of time practicing the correct way to start a note cleanly by coordinating the right air pressure from my lungs with precise use of my tongue on the reed. For a violinist, the attack is about the start of the bowing action; just listen to someone learning the violin to hear what getting it wrong sounds like! The attack is one of the main things that makes a sound individual. Big Ben’s clang is as much a part of its soundprint as the long warble and the Westminster melody.

  Eight months after hearing Big Ben’s crisp attack, I heard the complete opposite at a sound artwork. There are only a few examples of permanent sonic art in the world, and three of them are wave organs—in San Francisco in the US, Zadar in Croatia, and Blackpool in England. Blackpool is the archetypal British seaside resort, with its fish-and-chip shops, amusement arcades, and miles of sandy beach. It divides opinions: some see it as a mecca of lowbrow fun; others, as the epitome of tackiness.

  It was a typical English summer’s day when I visited: I had to wear a waterproof jacket to protect me from the cold wind rushing off the Irish Sea, and there were only intermittent glimpses of the sun. The organ stands behind a parking lot next to the promenade, with the UK’s tallest and fastest roller coaster generating distant screams from across the road. A narrow, rusting sculpture, 15 meters (50 feet) tall, shaped like a fern in spring beginning to unfurl, forms the most visible section of the wave organ (Figure 8.1). The sculpture is a popular spot to stop and light up a cigarette because it offers shelter from the wind. When I first arrived, the organ was only letting out the occasional groan. “Sounds like a moaning cow,” remarked a young woman as she walked past.

  Figure 8.1 The high-tide organ in Blackpool.

  High up in the rusty fern, I could see a few organ pipes, just like the ones you might see in a church. To get a better sense of what was going on, I climbed onto the tall seawall. Trailing down the concrete sea defenses was a set of black, plastic pipes that disappeared into the water. As the sea swells up, it compresses air in the plastic pipes, pushing the air up to the organ in the fern. Just as happens in a church organ, the air forced into the bottom of an organ pipe by the sea waves meets a constriction just below a rectangular slit in the side of the tube. The fast jet created there causes the air in the main part of the pipe to resonate, creating the tone.

  For any organ, the air needs to get up to speed quickly so that the pipe can start speaking cleanly. In this case, however, with the artwork being driven by water waves that flood and ebb irregularly, the notes often start tentatively and die away erratically—hence the groaning and moaning.

  The Blackpool organ is an aural rendering of the tidal conditions, a “musical manifestation of the sea,” according to the plaque on the side. So I waited around to see what would happen as the tide receded. After about half an hour, the water’s edge had dropped, and the movement of the water was more vigorous in the plastic tubing. The organ pipes that are tuned to higher-frequency notes began to play. The overall effect was now like a lazy orchestra of train whistles, or a slow-action replay of a nightmare recorder lesson.

  In another half hour the water’s edge only just covered the plastic pipes, and the organ was positively energetic. It produced random notes rapidly in an almost rhythmic pattern. The organ pipes were tuned so that the notes could blend together, but overall the sound reminded me of the simplistic computer-generated music I had made as a teenager—not something that many people would listen to for a long time, because the pattern of notes was too random. As discussed in Chapter 7, music works by subverting our expectations. Our brains enjoy hearing the unexpected, but only within reasonable limits. Listeners need an internal schema in their head for how things should be, that can then be subverted as the music progresses.1 The random notes from
the tide organ were just too unpredictable. As one of the artists who designed the work, Liam Curtin, said, “It will be an ambient musical effect and not a popular melody.” Furthermore, the organ never reprises its tune. Says Curtin, “On stormy days the performance is wild and frenzied and on calm days the sound is softer.”2 After a while the organ fell silent, as the sea dropped below the level of the plastic pipes on the beach.

  The attack of a sound helps us identify the source, whether that is a groaning wave organ, a conventional musical instrument, or Big Ben. Listen to trumpets, bowed violins, and oboes with the early parts of the notes artificially removed and they sound very similar, something like an early synthesizer from the 1980s. The initial scrape of the bow on the string, or the puff of air that parts the reed of the oboe, gives vital cues as to which instrument is playing. In the case of Big Ben, the rapid change in frequencies after the hammer has struck as it settles into a bong is the first cue that we’re listening to a bell.

  Many large bells warble. Six months after hearing Big Ben, I heard a distinct warbling effect when the Great Stalacpipe Organ played its hymn in Luray Caverns (see Chapter 2). The complicated shape of a stalactite close to me created two notes of almost the same frequency. The resulting tremor, known as beats, is caused by a simple addition of the sound waves, as illustrated in Figure 8.2. One note I analyzed had sound at 165 hertz and 174 hertz. These are close enough in frequency that a note at the average of 169 hertz is heard, with a loudness that rapidly changes at a rate given by the difference in the frequencies (9 hertz). A subtle warbling was added to the stalactite ring, adding a touch of sci-fi spaceship to the musical note.

  Figure 8.2 Two notes adding together to cause beats.

  Guitar players can use beats to help tune their instruments. They press the low string at the fifth fret and leave the next string open, plucking both notes simultaneously. If the two notes are slightly out of tune (that is, not at the same frequency), they will produce a warbling, which is caused by beats. Correctly adjusting the tension in one of the strings brings the two sounds closer in frequency. With a difference of about 1 hertz, the beats are slow enough to impersonate by saying “wowowowowow.” The beats get slower and slower as the notes become nearer in frequency, until they disappear altogether when the strings are in tune.

  For a bell, symmetry, or rather lack of it, causes the warble. If the bell does not form a perfect circle, it rings with two similar frequencies that beat together. When casting a new church bell, a Western foundry would normally want to avoid such a tremor. But in Korea, the effect is seen as being an important part of the sound quality. The King Seongdeok Divine Bell, cast in AD 771, is better known as the “Emille.” “Emille” means the sound of a crying child, and legend has it that the maker had to sacrifice his daughter to get the bell to ring.3 Big Ben beats distinctly because it creates two frequencies stemming from imperfections, with one flaw clearly visible. A large crack opened up on one side shortly after the bell was first installed. George Airy instructed that the bell be turned so that the crack was away from striking point, that a lighter hammer be used, and that neat square cuts be made at the ends of the crack so that it would grow no further.

  The slowly decaying ring of Big Ben produces a less dulcet tone than long notes played on wind, string, and brass musical instruments. A note is actually made up of a combination of sounds at different frequencies. There is a fundamental plus additional harmonics (overtones), which color the sound and change the timbre.4 Low notes on a clarinet sound “woody” and quite unlike a saxophone, even though both the clarinet and the saxophone are wind instruments driven by single reeds. The clarinet is a cylindrical tube, so it produces a different pattern of harmonics than does a saxophone with its conical bore. Comparing the harmonics of musical instruments and bells can help explain the differences in the sounds.

  Figure 8.3 presents an analysis of a note played on my soprano saxophone, showing the fundamental peak to the left and a whole set of spikes to the right that represent the harmonics neatly and regularly spaced in frequency. In contrast, the analysis of Big Ben’s ringing shown in Figure 8.4 reveals a forest of irregularly spaced spikes. The interplay between these harmonics is one reason a bell has a dissonant, metallic sound.

  Figure 8.3 A single saxophone note. (Sometimes the fundamental is called the first harmonic, in which case the subsequent peaks would be labeled second, third, fourth, . . . harmonics.)

  Figure 8.4 The ring from Big Ben.

  When two notes being played together appear to be fighting each other and clash, this is dissonance. At the core of Western music is the switching between tension-filled dissonance and harmonious consonance. A good example is the sung “amen” at the end of hymns, where the notes sung under the “a” feel unfinished, and the sound resolves only when the notes switch to those accompanying “men.” This feeling of tension being resolved is something we tend to enjoy.

  When two notes are played simultaneously, the sounds merge as they enter the ear canal. How we respond to the combined sound is partly dictated by how the harmonics align in frequency. For a simple interval like a perfect fifth (see Figure 8.5), where the notes sound pleasantly consonant together, the two sets of harmonic frequencies are nicely spaced.

  For a dissonant interval like a major seventh, however, the pattern of harmonics from the two notes is uneven (see Figure 8.6), with some peaks being close together. In the inner ear, where vibrations are turned into electrical impulses, sounds of similar frequency are actually analyzed together in ranges called critical bands. If two harmonics end up in the same critical band, but not at exactly the same frequency, then a rough, dissonant sound results.

  Dissonance and consonance are also exploited in sound art. Harmonic Fields is an artwork by French composer Pierre Sauvageot, which I visited six months before my trip to Big Ben. As I approached by bus, I could see a forest of wind-driven musical instruments atop Birkrigg Common, a hill near Ulverston in the English Lake District. In medieval times the raised location would have been a good spot for a castle, but now it is a prime location for catching the prevailing westerly winds. Leaving the bus behind, I walked up the hill with some trepidation. The air seemed very still, and I feared the instruments would be silent. But as I approached a tall scaffold with baubles hanging from drooping metal branches, I was relieved to hear it hum.

  Figure 8.5 Two combined saxophone notes that sound consonant.

  Figure 8.6 Two combined saxophone notes that sound dissonant.

  Harmonic Fields is a huge artwork with hundreds of different musical instruments. It has few visual charms—just industrial-looking wires, orbs, and scaffolding set out here and there in a confusing pattern. The artist requests that visitors do not take pictures but rather concentrate on the sounds. I slalomed through lines of vertical bamboo poles, which whistled like a panpipe ensemble on opiates. They made sounds like a flute; as jets of wind hit the edges of slits in the wood, the air column inside the bamboo resonated. I walked the length of a wire that looked like a zip line, pausing to poke my head into a drum, which was attached to the middle. The drum amplified the vibration of the wire, producing a tone just above middle C, a note in the center of a guitar’s range. But the hum was not constant; it waxed and waned, sounding like a wet finger being run around the rim of a large wineglass.

  My favorite piece was very simple and unassuming. Plastic strips were strung between tripods like clotheslines. When I first walked over to it, I kept looking up for the helicopter overhead that was ruining my recording, until I realized the “whop-whop-whop” was actually coming from the strips themselves, which were acting as a giant Aeolian harp.

  When wind passes over a wire, the air above and below has to speed up to get around. A fast-moving stream of air flows away behind the wire, moving into the space just behind the wire, switching between two states: first the airstream from above fills the space, and then the stream from below. This alternating airstream causes the wire to vibrate back
and forth and create a tone.5 The same phenomenon happens on a vast scale as air flows past islands, as can be seen from satellite pictures of clouds like the one in Figure 8.7. For the Aeolian harp, both the frequency and the loudness of the sound change as the wind speeds up and slows down, so the tone is forever altering.

  Figure 8.7 Satellite image of clouds showing airflow around Alejandro Selkirk Island, Chile. (The island is in the top left of the image. The whorls behind it are oscillating wakes, a visual demonstration of turbulence.)

  I once presented a radio program titled “Green Ears” about sound in the garden, and all the experts I interviewed hated wind chimes. For those gardeners, some parts of Harmonic Fields would have been like wind chime hell, where a forest of glockenspiels rang with the maniacal strikes of mallets driven incessantly by turbines. Pierre Sauvageot sees the whole work as a musical composition, “a symphonic march for 1,000 [A]eolian instruments and moving audience.”6 Hence, the wind instruments are carefully tuned to play particular notes, which combine to produce in some places sweet harmony and in others, a malevolent dissonance like a swarm of insects.

  Because consonance and dissonance underpin music, they have also played a central role in the debate over why humans have evolved to like music. Thomas Fritz of the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, wanted to see how people who have not been exposed to Western music responded to consonance and dissonance, so he traveled to Cameroon in Africa to study the Mafa people. The Mafa are located in the extreme north of the Mandara mountain range. The most remote settlements have no electricity supply and are culturally isolated by pervasive illnesses such as malaria. The Mafa make ritual sounds, and Thomas once played an example for me. It sounded like a dissonant chorus of old car horns, but actually the noise came from vigorously blown flutes. Thomas compared the responses of the native Africans to Westerners, playing both groups a variety of music styles from rock and roll to the Mafa’s ritual sounds, including versions of all the pieces that had been electronically processed to make them sound continuously dissonant. Both groups showed a preference for the less dissonant original pieces over the manipulated versions.