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

by Trevor Cox

  To Deborah

  Contents

  Prologue

  1 The Most Reverberant Place in the World

  2 Ringing Rocks

  3 Barking Fish

  4 Echoes of the Past

  5 Going round the Bend

  6 Singing Sands

  7 The Quietest Places in the World

  8 Placing Sound

  9 Future Wonders

  Acknowledgments

  Notes

  Index

  THE SONIC WONDERS OF THE WORLD

  Prologue

  “Is it safe?” A noxious odor was invading my nostrils as I stared down the open manhole. The metal ladder disappeared into the darkness. I had assumed a radio interview on the acoustics of sewers would involve an official and authorized visit. Instead, it started with a walk into a London park on a summer’s evening. Bruno, the interviewer, produced a large key from his knapsack, opened up a convenient manhole cover, and invited me to climb down. Was it legal to wander around the sewers without permission? What if the tunnel suddenly flooded? What about a canary to warn of poisonous gases? Meanwhile, strolling commuters ignored us as we gazed into the gloom.

  I repressed my anxieties and climbed gingerly down the ladder to the sewer about 6 meters (20 feet) below. This was a storm drain built in Victorian times, a long cylindrical tunnel lined with bricks. The floor was treacherous and slippery, and the odor made my skin crawl. I clapped my hands as best I could with rubber gloves on and started to count in my head very slowly—“one, two, three, . . .”—timing how long it took the sound to die away. After 9 seconds a distant rumbling echo returned to me. Sound travels a kilometer (about a half mile) every 3 seconds, so my clap had traveled a round-trip of 3 kilometers (1.9 miles). Later on, far away down the tunnel, we discovered the staircase off which the sound had bounced; it was draped in disgusting debris.

  I found it difficult to avoid head-butting the stalactites hanging from the low ceiling. Sadly, these were not brittle rock, but crusty, fatty deposits clinging to the bricks. These foul stalactites broke off, worked their way down the back of my shirt and scraped my skin. Since I’m tall, my head was very close to the ceiling—the worst place for the revolting stalactites, but the optimal position for observing an unexpected acoustic effect. As the radio interview started, I noticed my voice hugging the walls of the cylindrical tunnel and spiraling into the distance. Speech spun around the inside of the curved sewer like a motorcyclist performing in a Wall of Death. While every other sense was being overwhelmed with revulsion, my ears were savoring a wonderful sonic gem. This impressive spiraling toyed with me as I tried to work out what was causing the effect. It was so different from anything I had experienced before that I started to doubt what I was hearing. Was it just an illusion, with the sight of the cylindrical sewer fooling my brain into thinking the sound was curving? No; when I closed my eyes, the reverberance still embraced my voice and twisted it around the tunnel. What was causing the sound to stay at the edges of the sewer and not cross into the middle? I have worked in architectural acoustics for twenty-five years, yet the sewer contained a sound effect I had not heard before. I also noticed that Bruno’s voice was embellished with a metallic twang as it echoed in the sewer. How was that possible in a place devoid of metal? We were surrounded by bricks.

  During those hours listening to the sewer, I had an acoustic epiphany. My particular expertise is interior acoustics—that is, the way sound works in a room. Most of my work has focused on discovering ways to mask or minimize unwanted sounds and acoustic effects. Not long after completing my doctorate, I pioneered new ways of shaping room surfaces that now improve the sound in theaters and recording studios around the world. Above the stage of the Kresge Auditorium at the Massachusetts Institute of Technology, you can see the gently undulating reflectors I designed to help musicians hear each other. For a rehearsal hall at the Benslow Music Trust in Hitchin, England, I designed corrugations to adorn a concave wall in order to stop sound reflections from all being focused onto a single point in the room and thereby altering the timbre of the musical instruments.

  In recent years I have been researching how poor acoustics and high noise levels in classrooms affect learning. It seems obvious that pupils need to be able to hear the teacher and have a certain amount of quiet to learn, yet there are architects who have designed schools that are acoustic disasters. My bête noire is open-plan schools, where doors and walls are dispensed with, resulting in the noise from one class disturbing others because there is nothing to impede the sound. The Business Academy Bexley in London opened in 2002 and was short-listed for the prestigious Royal Institute of British Architects’ Stirling Prize. The open-plan design caused so many noise problems, however, that the school and local education authority had to spend £600,000 ($0.9 million) installing glass partitions.1 Part of my research into schools involved playing noise at pupils as they tried to complete simple tasks involving reading comprehension or mental arithmetic. In one test, playing the babble of a noisy classroom at a cohort of fourteen- to sixteen-year-olds lowered their cognitive abilities to those of a control group of eleven- to thirteen-year-olds who were working in quieter conditions.

  I am currently working with colleagues to improve the quality of user-generated content online. I started the project after getting frustrated listening to distorted and noisy soundtracks on Internet videos. We are developing software that will automatically detect when an audio recording is poor—for instance, checking whether there is wind noise whistling past a microphone. The idea is to alert users to poor sound conditions before they start recording, or to use audio processing to weed out some of the interference, just as a digital camera looks for flaws and automatically adjusts exposure time and focus. But before we can write the software, we are grappling with people’s perceptions of audio quality. When you record your child playing in a school concert, does the quality of the recording matter very much? My personal feeling is that audio distortions can be much more important than visual ones. A blurry video with a clear recording of a loved one singing captures that special moment much better than a clear video in which the lyrics are unintelligible and the voice distorted.

  But as I splashed about in the sewer, I realized that distortions can sometimes be wonderful. Despite having studied sound intensely for decades, I had been missing something. I had been so busy trying to remove unwanted noise that I had forgotten to listen to the sounds themselves. In the right place a “defect” such as a sound focus, or the metallic, spiraling echo in the sewer, could be fascinating to listen to. Perhaps ugly, strange, and distorted sounds could teach us something about how acoustics works in everyday situations or even how our brain processes sound. By the time I emerged out of the sewer through a manhole in a leafy suburban street, I decided I wanted to find more such unusual acoustic effects. And not just the ugly ones. I wanted to experience the most surprising, unexpected, and sublime sounds—the sonic wonders of the world.

  Somewhere on the vast Internet I imagined I would be able to find a list of other strange sounds to experience. But after a lengthy shower scrubbing away the odorous memory of the sewer, and a few hours online, I realized it would not be so easy. The dominance of the visual has in fact dulled all of our other senses, especially our hearing. Our obsession with sight has led us to produce loads of images of bizarre and beautiful places, but surprisingly few recordings of wonderful sounds. Like the Soundkeeper in Norton Juster’s classic children’s book The Phantom Tollbooth, I sense among my fellow citizens a lack of appreciation of subtle sounds and an increase in discordant noises.2 B
ut rather than lock away sounds and enforce silence as the Soundkeeper does, I wanted to seek out, experience, and celebrate wonderful aural effects. What fascinating sounds are out there if we just “open” our ears? While there are many books on unwanted noise and how to abate it, there are not many on how to listen better—something acoustic ecologists call ear cleaning.

  Open [a] book now and gently open the pages and just listen to the sound . . . that’s a very complex sound . . . first there is the sound of the thumb or finger as it brushes against the edge of the paper before you turn the page and then there is the sound of the page as it turns.3

  This is Murray Schafer, the grandfather of acoustic ecology, demonstrating how even a simple object, such as the book in your hands, can make many different sounds. It is “full of possibilities,” he writes. This quote from an ear-cleaning exercise comes from a Canadian radio program from the 1970s. No cotton swabs are involved, however; listeners improve their hearing skills by changing how their brains process sound, not by physically cleaning their ears.

  Schafer tells his listeners to remove all distractions—“like eating, drinking or smoking: well smoke if you have to but don’t let it distract you”—to control your breathing and close your eyes to “amputate the visual sense.” The experience could be disconcerting, because although the radio script is reminiscent of a meditation CD, the bossy narration is far from soothing. The recording reminds me of a scene from an old black-and-white espionage film in which a villain is trying to brainwash the hero.

  Despite the unnerving tone, the program includes some intriguing exercises: invent an onomatopoeic name for the sound of a hardback book being slammed shut (thump or thud does not quite work), or predict and then imitate the sound of a piece of paper being scrunched up and thrown against a wall. Nowadays you might have to choose something different to play with—an e-book reader being dropped in the bath?

  Schafer is evangelical about ear cleaning, believing that children should do it to improve their sonic sensibilities, and that people who shape our sound world, such as urban planners, should undergo the process regularly. In his seminal book The Soundscape, Schafer suggests some other ear-cleaning activities you could try. The technique he uses most often is to get people to declare a moratorium on speaking for a day, while eavesdropping on sounds made by others. He wrote, “It is a challenging and even frightening exercise,” and successful participants “speak of it afterward as a special event in their lives.”4 But my colleague and fellow acoustic engineer Bill Davies believes this is taking it too far: “If you want to give people an acoustic epiphany,” he told me, “then a short journey on a soundwalk is a better way of going about it.”5

  A soundwalk can be a simple activity. All one has to do is stroll for a couple of hours without saying a word, focusing intently on the sounds of the city or countryside. I first did this with an eclectic group of thirty engineers, artists, and acoustic ecologists. We formed a slow-moving strung-out crocodile weaving through the streets of London. The cacophony of cars, planes, and other people starkly contrasted with our own enforced silence. I felt like an extra in an old B movie, part of a procession of possessed humans being summoned by some alien force—silent zombies walking toward impending doom.

  This particular group was re-creating a soundwalk that Murray Schafer and colleagues had first carried out in the 1970s. We followed a set of prescribed exercises—from trying to count the number of propeller aircraft heard flying over the formal gardens in Regent’s Park (pointless nowadays, though you can still count jets), to trying to suppress a loud noise by consciously ignoring it. I chose the loudest sound around, a pneumatic drill that was hammering away on Euston Road.

  Ignoring a pneumatic drill proved very hard to do; indeed, at first it seemed impossible. Trying to disregard the pounding noise immediately made it more obvious because of the way our hearing works. Seals might be able to close their outer ears when diving, but humans have no way of physically shutting out sound. We have no “earlids,” and there is no auditory equivalent of closing our eyes or averting our gaze. Our hearing is constantly picking up sounds. We cannot physically stop the eardrum, the tiny bones in the middle ear, or the tiny hair cells in the inner ear from vibrating. Inevitably, the inner ear generates electrical signals, which travel up the auditory nerve into the brain. Fingernails scraping down a blackboard or the climax to a Beethoven symphony, good sounds or bad—the ear sends the audio upward. The brain then has to work out which sounds are important and must be paid attention to, and which ones can be safely ignored. Something noisy and abrupt, like the roar of a tiger or the squealing of car brakes, catches our attention immediately so that we can fight or take flight. When we hear something less threatening, we have to think and decide which sound we want to attend to.

  Auditory attention was first researched after the Second World War, as the military tried to understand why fighter pilots sometimes ignored crucially important audible messages.6 A typical experiment had people listening on headphones and saying aloud the words they heard through one of their earphones. Simultaneously, researchers played a distracting message in the other ear. After this test, subjects could recall very little about the distracting message. Scientists would make changes to the distracting speech—switching talkers or language, and even playing the sound backward—yet most people failed to spot the changes.7 Although many of us believe we listen to multiple sounds simultaneously, and even believe that women are better than men at such multitasking, these tests demonstrate that such an ability is an illusion. We listen to one thing at a time and rapidly change our attention from one sound to another.

  Consequently, back on Euston Road the only way to quiet the pneumatic drill was to focus very hard on another sound. I used two strangers having a boisterous conversation outside a pub. Trying to actively suppress the drill just made it louder, but switching my attention elsewhere meant I could exploit the brain’s amazing cognitive ability to suppress background noise.

  During the hours focusing on the soundscape around me, I heard the fleeting melody of birdsong, an unexpected hush in the piazza outside the British Library, an auditory sense of enclosure as I entered the tunnel under Euston Road, and the subtle squelching of an underinflated bicycle tire on pavement. Interesting sounds suddenly became more obvious and audible. I was amazed to hear how different railway stations sounded; the throb of idling diesel trains in King’s Cross made that station seem more authentic than St. Pancras or Euston. Of course, it was not all positive; the clatter of cheap rolling suitcases being dragged along platforms and sidewalks proved intensely annoying.

  Acoustic ecologists have amazing ears for such sonic subtleties, but soundwalking and ear cleaning can help anyone learn to consciously tune in to such previously overlooked delights. We have at our disposal immense cognitive power to analyze sound—after all, listening to and decoding music and speech is an incredibly complex task—yet it is something we take for granted. A soundwalk reveals that there are sounds in our everyday life that, if we choose to listen to them, will surprise us with their diversity and uniqueness. Even something as mundane as footsteps encompasses a huge range of sounds, from the clack-clack of high heels on marble, to the squeak of sneakers on a gym floor. If we can unconsciously learn to recognize colleagues approaching unseen along a corridor from the rhythm of their walking, what else might we be able to accomplish with dedicated effort? Our ears play an immensely important role in how we perceive the world. In this book I hope to show how we can filter things differently, to move us away from our overreliance on the visual, showing how diverting our attention in this way can enrich our enjoyment and understanding of the spaces we inhabit.

  Acoustic ecologists are also concerned with aural conservation. Soundscapes do not need to be preserved in aspic, but we need to make sure that great sounds are not lost through neglect—not just calls from endangered species, but also other sounds that are important to us. Not long after my first soundwalk, I interview
ed artists in Hong Kong for a BBC program about endangered sounds. They lamented the loss of the bells in the tower at the Star Ferry pier in Kowloon in 2006, which used to play the Westminster Chimes. Redevelopment and well-meaning renovations can ruin precious acoustic effects, as happened about a century ago in the US Capitol in Washington, DC, when architects altered the dome and dulled the focusing that used to distort the speech of senators. Acoustic scientists and historians have only recently begun documenting, preserving, and reconstructing the acoustics of a very few important places. Combining the latest methods for predicting architectural acoustics, three-dimensional sound reproduction, and new archaeological research, scientists have begun to reveal some of the ancient sounds of Greek theaters and prehistoric stone circles.

  Another major threat to the sonic landscape is the smog of transportation noise. Underwater, baleen whales have to sing louder to overcome shipping noise. In cities, birds such as great tits have changed their tunes to be heard above the traffic. Of course, humans suffer as well: Nearly 40 percent of Americans want to change their place of residence because of noise, 80 million EU citizens live in unacceptably noisy areas, and one in three UK citizens have been annoyed by neighbor noise.8 Unintelligible announcements in train stations, restaurants where you have to shout to hold a conversation, and annoying mobile phone ringtones—we unnecessarily suffer a large number of acoustic deficiencies.

  Some of these sound excesses are of our own making. Many of us take a large daily dose of music and speech through headphones that isolate us from the sound of our environments. It has become part of our daily routine: compared with only five years ago, youngsters spend 47 more minutes a day listening to music and other audio.9 We drive around in cars cocooned in our own portable and controllable soundscape. But then we miss out on simple sonic pleasures: not just the twitter of a bird singing out defiantly against the roar of traffic, the laughter of schoolchildren in a playground, or a snippet of overheard gossip from strangers passing in the street, but the wonderful and unique acoustics of the places we wander through each day. City districts can be visually ugly, but even there, a dingy corner covered in graffiti can harbor the most extraordinary zinging sound effects.