On Looking: Eleven Walks With Expert Eyes (28 page)

Cities are crowded with sources of sound regularly approaching this threshold of hearing loss. There are biological reasons for why we are so afflicted: our ears are designed to let in the frequencies at which we speak—from a few hundred to a few thousand hertz. Enormous numbers of man-made sounds occur in those same frequencies. We often find high pure tones the most irritating: the screech of a subway turning a tight corner or braking, at 3,000 or 4,000 hertz, or the sound of fingernails on a chalkboard, between 2,000 and 4,000 hertz. These sounds clobber us because
of the shape of the human ear, which allows high frequencies to find their way efficiently to the cochlea. The very design of the ear amplifies these vibrations for waiting hair cells. But it is not just our ears that find the sound distressing; it is our brains. If we know that we are hearing what we have already deemed an “annoying sound,” our bodies react to it as though it is: we have a sympathetic nervous system response, usually reserved for final exams, suddenly appearing lions, and the sight of our beloved. We sweat, and then we notice that we are sweating, and we sweat some more.

As Lehrer and I walked down the street in the wake of the motorcycle’s roar, I noticed myself curling my hair around my left ear to expose it for better listening to what he had to say. This was perfunctory: our hearing is exceedingly sensitive, whether covered with uncurled hair or not. As Lehrer spoke, sound energy was heading down the winding caverns of my outer ear and being conducted through slender bones, making a membrane vibrate and those tiny hair cells dance. The force required to move our dancing ear hairs is so minimal that it would disrupt the tiniest mosquito not at all.

Unlike our other senses, in listening, the normally functioning ear actually makes its own noise, something called otoacoustic emissions. Though we do not generally hear these sounds ourselves, they are suggested to be sufficiently distinctive that they could be used as aural signatures to identify individuals. I inclined slightly toward Lehrer and listened for his. Nothing. Instead, a familiar sound, that of a compact, dense object making quick contact with a softer solid mass—
thwack!
—banged in our canals.

We both turned to our right, detecting the direction of the sound at once, coming from beyond a chain-link fence. A boy was throwing a softball with an older man in a mostly empty schoolyard. Water puddled along the corners of a basketball court; a
set of bleachers sat unused. I reflexively grabbed the chain-link as though it would help me hear better while I peered through it. Sounds of a school playground: is there anything more evocative of childhood? The bounce of different kinds of balls on the court or in hand, the shrill cries of children hopping or running or dodging one another or in hot pursuit, the slap of a jump rope on asphalt, the rattle of a ball off a backboard. In the corner of the yard was a set of playground equipment and, whether I saw them or not, I thought of swings—impossibly squeaky swings, standard-issue rubber seats, bowed by the heavy bodies of children, tracing wide arcs. I have not only sat in uncountable swings, but I now sit my son in the city’s playground swings on a regular basis, controlling the pace of the squeaking by pushing him faster or slower.

Just seeing the playground called forth a memory
(my own son swinging)
and evoked a clear feeling
(how magnificent this little boy is)
that nearly replaced my perception of the sight and sounds right in front of me. Awakened was the memory of the weight of his body as I pushed him, of looking at his cold hands gripping the chain in winter, of wondering how high is too high; and even of my own childhood, wondering what it would be like to jump off a swing and then, one day, after watching other kids do it hundreds of times, letting go, feeling the slice of space that formed between me and the seat, and then falling. It was nothing like my anticipation. It was like being lifted up by a benevolent soft hand.

I closed my eyes and half-shook my head to return to the present. To pay attention to one’s sound memories is to open the door to a closet bursting at the hinges: something is stuffed just inside, on the edge of falling out and into your consciousness. In the present, Lehrer was talking. And I quickly returned my focus to his voice, for he was talking about squeaking sneakers.

“
That
is one of the keynote sounds of the schoolyard,” he said,
referring to Schafer’s idea of those elements of a soundscape that may not be consciously attended to but are characteristic of a space. The ball-tossing boy was wearing orange high-tops, and I tried to match his foot movements to the squeaking I was hearing. It was a basketbally sound. So basketbally, in fact, Lehrer said, that televised pro basketball places microphones on the court itself to pick up the sound of the squeaks. “They know that’s an exciting sound, hearing all those basketball sneakers maneuvering.” The rambunction!

I wondered if the engineers ever ramped up the sound for greater effect.

“Oh, absolutely!” said the sound engineer.

We lingered a while by the schoolyard. Two teenage boys entered from stage right and headed for the basketball court stage left. One leapt up, his hand extended for the rim, the other added the twang of a dribbled basketball to the space. It hit us like the smell of a ripe melon in our faces. I asked Lehrer why the sounds were so crisp and ringing here. It would not be a good place to hold a chamber music concert, but it was full of bright, loud sounds.

“It’s all pretty simple physics,” he claimed. All sound travels at the same speed, around eleven hundred feet per second. So if one takes into account the distance from the sound source to the surrounding surfaces, and looks at what those surfaces are made of, the result is a decent approximation of what the listener will experience. In this space, with three brick walls and an asphalt surface underfoot, “It’s very reverberant.” The softball tossers were close to the back wall; the basketballers were near a side wall. Their proximity to the walls reinforced the sounds they were making. “If you listen,” Lehrer said, “you can hear the early echoes, when the sound really snaps. . . . You won’t hear the echo off that [first] wall as being a separate sound; it just reinforces the original sound, making it sound louder.” For the other walls, another eighty feet
away, we estimated, it would take seventy milliseconds for the sound to reach it and come back to our ears, making a second sound—“which is perceptible: it sounds like
TIH-ka
.”

The reason we could not distinguish the sounds of the basketball or the softball from their first, early echoes is that the near walls were less than twenty or so feet away. The human ear does not have the acuity to distinguish similar sounds made less than forty milliseconds—less than 1/20th of a second—apart. The sounds blur together, making a single larger sound cloud. Lehrer takes advantage of this auditory phenomenon in his live-sound work when he needs to control the “articulation” or the intelligibility of the sound system: if he uses a speaker in a theater to amplify the sound from the stage, it had better be set up so that the audience hears the sound from the speaker synchronized with the sound onstage. Given the way our ears work, though, there is room for error—about forty (or less) milliseconds’ worth—which means that a speaker can be set about fifty feet away and few people will hear the sound as echoing.

The amount of reverberation of sound in a space like this schoolyard is what Lehrer called the “wetness” of the space. This space was pretty wet. (And full of puddles, too, by coincidence.) Wetness is something a sound engineer can manipulate in a recording, turning it up or down for effect. Deep inside the museum a half an hour earlier we had walked through small rooms with carpets on the floors and weavings on the walls: these were “dry” rooms. The driest rooms are studios, acoustically “dead” rooms with minimal reverberation, which allows the sound mixer to control the sound effects himself, rather than leaving it to the room to define the sound. The wetness of a room, and the kinds of early reflections and echoes one hears, are, Lehrer said, “what makes rooms sound like ‘rooms’ to us—why a bathroom sounds different from a living room, sounds different than the kitchen.”
It has to do with the size of the space, the distance to the walls, the objects within, and the surfaces of those objects.

Despite my familiarity with rooms, this was a kind of noise I had never listened for. Nonetheless, I could at once assent that yes, it seemed likely there was a definitive bathroomlike sound—hence, all the singing that goes on in bathrooms but not in dining rooms. Of course, we do think about these sounds when they are dissonant with what we see. Should a kitchen scene in a movie have a “bathroom sound” to it, the audience might notice something is off. Sound engineers compile and keep catalogs of specific room sounds, each with the right set of reflections and reverberations and frequency content. “I have my ‘bathroom preset,’ ” Lehrer said, “and we plant the actor’s voice”—recorded not in the bathroom but in a dry room in a studio somewhere—“into that reverb unit. What comes back is something that gives you the sense that the person is in the bathroom.”

I vowed to listen for my office sound when I returned home. I wondered if it made a sound without me in it.

Lehrer and I reluctantly turned from the schoolyard and headed down the street. Passing under a low scaffolding, I remembered Gordon hearing the sound of the enlarged awning with her probing cane. Lehrer heard the change, too. We paused and smiled with the assumption of shared recognition at a clutch of tourists walking in the other direction. They did not appear to understand why these crazy people were giddy at the scaffolding. As we approached an avenue, the air became thicker with sounds: people moving and chattering, birds overhead, eighteen-wheelers and buses roaring downtown. A metal pipe dropped somewhere and banged three bangs before settling.

Among the rumbles and crashes, crowd noises and traffic, I felt impressed that I could hear and understand every word that Lehrer was saying—and he, I. Psychological science names this
the “cocktail party” effect: the ability, demonstrated most characteristically when at a noisy party, to distinguish what the attractive person in front of you is saying from the general din of the room. We do this terrifically well, as a species. Even better, if someone three conversations to our right happens to mention something of interest to us—such as our name, or the name of someone we know—we are often able to tune right over to that conversation, like a perfectly smooth radio dial.

How we do this is still somewhat of a mystery, but one clue comes from “auditory restoration,” or, less jargonly, perceptual filling-in. You have almost certainly experienced this phenomenon without knowing it. When you are listening to, say, a friend talking, it is rarely in a perfectly quiet environment. Regularly, other sounds are louder than and intrude on the speech sounds coming out of your friend’s mouth. We only notice this when the noises drown out all speech; most of the time, noise might mask what the person is saying, but we do not miss a beat. Our brains spontaneously fill in the gap, constructing the sound that was missed. We do not even have the experience of missing it, so smooth is the filling-in.

If you are skeptical, consider the visual blind spot, which prompts the visual analogue of our auditory restorative process. By “blind spot,” I do not mean the metaphoric blind spots we all have for the elephants right in front of us. I mean the hole in our visual field created by the anatomy of the eye. The retina, at the back of the eye, is slathered with photoreceptors that convert light to electrical signals. There are so many that any light that hits our eyes will inevitably hit one of these receptor sites; with our eyes open and daytime in front of us, we spontaneously and immediately create an image of a full, dynamic visual scene. But. Just one thing. Right in the middle of the retina there is a small hole. In a strange design twist, this hole is the necessary exit route for
the nerve cells from the eye: the tunnel through which the optic nerve, ushering all the visual information that has hit the retina into the brain, leaves the eye. Where there is a hole, though, to let the wiring through, there are no receptors. So any light that hits that part of the retina is not noticed by our eyes or our brains. We
should
see a small black hole in front of us every time we open our eyes. We do not see that hole, however, because our brains, clever tissues, swoop in to pick up the slack. Our brains
fill in
the hole with what it expects to be there. We are constantly, fluidly making up what we see.

Given our ability to “see” things our eyes do not see, it should not be surprising that we “hear” things our ears do not hear. Still, this feat of auditory filling and sorting is nothing compared to that accomplished by other animals. Take bats. For most species of bats, which, though not blind, evolved to navigate by echolocating, tuning in to a conversation on a noisy street would be child’s play. Echolocating bats
see
the world by
hearing
it, and they hear it by emitting high-frequency calls from their nose or mouth and then listening for the sounds to bounce back to them, all while maneuvering at high speeds. The intensity and the speed at which the sounds come back allow bats to construct a picture of their environment on the fly. Their sound vision is acute: it enables them to catch their prey—usually insects themselves working hard to avoid detection—on the wing.
⁵
It allows them to distinguish soft objects from hard; note whether an object is far, near, or very near; even distinguish between types of trees. New York City’s little brown bats must successfully discriminate the broad-leafed London plane from the maples and oaks. Even more incredibly, all this parsing and organizing of the sounds of the world happens
while dodging branches and swooping in on prey. Bats need to adjust their picture of their environment as they move, and they do this by instantaneously changing the rate, pitch, and loudness of their calls according to what they are hearing. Then they are faced with a further challenge: as social animals, bats are always around other bats—all calling and flying themselves. Sometimes thousands of them flit about together in a small space. How they distinguish the sounds of other bats calling from their own echoes, and from the warnings and solicitations that are a normal part of bats’ communication with one another, still puzzles researchers. It does appear that once in a while their strategy is just to go quiet.