The Sound Book: The Science of the Sonic Wonders of the World (32 page)

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.
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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.”
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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.

M
any 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.
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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.

T
he 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.
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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.