Hearing: The Fourth Dimension
By john Kord Lagemann
Our world is filled with sounds we never hear. The human auditory range is limited to begin with: if we could hear sounds lower than 20 vibrations per second, we would be driven mad by the rumblings and creaking’s of our muscles, intestines and heartbeats; every step we take would sound like an explosion. But even within our auditory range we select, focus, pay attention to a few continually “turn off.” But in the process we shut out the glorious symphony of sound in which the living world is bathed.
Everything that moves makes a sound, so all sounds are witnesses to events. Thus sound is a kind of fourth dimension, telling us what is going on, revealing nuances and complexities opaque to vision alone. If touch is the most personal of senses, then hearing-an outgrowth of the sense of touch, a highly specialized way of touching at a distance – is the most social of the senses.
The sound-tormented city dweller who habitually “turns off his audio” loses a dimension of social reality. Some people, for example, possess the ability to enter a crowded room and from the sounds encountered know immediately the mood, pace and direction of the group assembled. Everything becomes more real when heard as well as seen. It is, in fact, quite hard really to know a person by sight alone, without hearing his voice. And it is not just the sound of the voice that informs. Even the rhythm of footsteps reveals age and variations of mood-elation, depression, anger, joy.
For these reasons, hearing has a kind of primacy for the social being called man. A baby responds to sound before the does to sight, smell or taste. This is good evidence that the human fetus listens to its mother’s heartbeats weeks before birth. This may explain why babies are easily lulled to sleep by rhythm, and why their first words are repeated syllables-da-da, ma-ma, gee-gee—that sound like the lub-dub of the heartbeat.
All through life, hearing is a major channel of experience, a more vital stimulus than vision. It is also the watchdog sense. Since there is no sound without movement of some kind taking place, sounds warn us of happenings. When we go to sleep, our perception of sound seems to be the last door to close, and the first to reopen as we awaken. Even as we asleep, the brain is alerted by certain key sounds. A mother wakes at the whimper of her baby. The average person is quickly roused by the sound of his own name.
Watchdog, stimulator, arouser-it is not surprising that modern urban man has turned down and even crippled this most stressful of sense. But hearing can also soothe and comfort. The snapping of logs in the fireplace, the gossipy whisper of a broom, the inquisitive wheeze of a drawer opening all are savored sounds that make us feel at home. In a well-loved home, every chair produces a different, recognizable creak, every window a different click, groan or squeak. The kitchen by itself is a source of many pleasing sounds-the clop-clop of batter stirred in a crockery bowl, the chortle of simmering soup, the conversational maundering of an electric percolator on the breakfast table. Every place, every event has a sound dimension.
The sense of hearing can perhaps be restored to modern man if he better understands its worth and how it works. Most people would be surprised to discover how far the sense can be pushed by cultivation. At a friend’s house once, my wife opened her purse and some coins spilled out, one after another, onto the bare floor. “three quarters, two dimes, a nickel and three pennies,” said our host as he came in from the next room. And, as an afterthought: “one of the quarters is silver.” He was right, down to the last penny.
“How did you do it?” we asked. “try it yourself,” he said. We did, and with a little practice we found it easy. On the way home my wife and I took turns closing our eyes and listening to the sound of our taxi on the wet street as it reflected from cars parked along the curb. Just from the sound we were able to tell small foreign cars from larger American cars. Such games are one of the best ways to open up new realms of hearing experience.
An allied beneficence of hearing is that “extrasensory” faculty of the blind called facial vision. Doctors have long marveled at this sensitivity to reflected sound. About 200 years ago, Erasmus Darwin, grandfather of Charles Darwin, reported a visit by a blind friend, one Justice Fielding. “he walked into my room for the first time and , after speaking a few words, said, ‘this room is about 22 feet long, 18 wide and 12 high’- all of which he guessed by the ear with great accuracy.”
Sound engineers call it “ambiance,” the impression we all get in some degree from sound waves bouncing off walls trees, even people. For a blind person to interpret the echoes effectively he uses a tapping cane preferably with a tip of metal nylon or other substance that produces a distinct, consistent sound. (wood gives a different sound wet than dry.) the metal noisemaker called a “cricket” is equally effective. Animals, both terrestrial and non-terrestrial, also use “echo-location.” The bat, for example emits a very high-pitched sound and picks up echoes from any obstacle, even as thin as a human hair.
The human ear is an amazing mechanism. Though its inner operating parts occupy less than a cubic inch it can distinguish from 300,000 to 400,000 variations of tone and intensity. The loudest sound it can tolerate is a trillion times more intense than the faintest sounds it can pick up-the dropping of the proverbial pin, the soft thud of falling snowflakes. When the eardrums vibrate in response to sound the tiny piston-like stirrup bones of the middle ear amplify the vibrations. This motion is passed along to the snaillike chamber of the inner ear, which is filled with liquid and contains some 30,000 fibers. These fibers are made to bend, depending on the frequency of the vibration –shorter stands respond to higher wavelengths longer strands to lower –and this movement is translated into nerve impulses and sent to the brain, which then, somehow, “hears.”
While we are still under age 30, most of us can hear tones as high as 20,000 cycles per second (c.p.s), about five times as high as the highest C on a piano. With age, the inner ear loses its elasticity. It is unusual for a person over 40 to hear well above 10,000 c.p.s. He can still function, of course, since most conversation is carried on within an octave or two of middle C, or about 260 c.p.s.
Curiously, evidence indicates that people need sound. When we are lost in thought, we involuntarily drum with our fingers or tap with a pencil- a reminder that we are still surrounded by a world outside ourselves. Just cutting down reflected sound can produce some odd results. The nearest thing on earth to the silence of outer space, for example is the “anechoic chamber” at the Bell Telephone Laboratories in Murray Hills, N.J., which is lined with material that absorbs 99.98 percent of all reflected sound. People who have remained in the room for more than an hour report that they feel jittery and out of touch with reality.
One remarkable quality of the human ear is its ability to pick out a specific sound or voice from a surrounding welter of sound, and to locate its position. Toscanini rehearsing a symphony –Chestra of almost 100 musicians, unerringly singled out the oboist who slurred a phrase. “I Hear a mute somewhere on one of the second violins,” he said another time in stopping a rehearsal. Sure enough, a second violinist far back on the stage discovered that he had failed to remove his mute.
We owe our ability to zero in on a particular sound to the fact that we have two ears. A sound to the right of us reaches the right ear perhaps. 0001 second before it reaches the left. This tiny time lag is unconsciously perceived and allows us to localize the object in the direction of the ear stimulated first. If you turn your head until the sound strikes both ears at once, the source is directly ahead. Primitives, to pinpoint the source of a sound, slowly shake the head back and forth. Try it sometime when you hear the distant approach of a car. The sound you hear most often and with greatest interest is the sound of your own voice. You hear it not only through air vibrations which strike your eardrums but through vibrations transmitted directly to the inner ear through your skull. When you chew on a stalk of celery the loud crunching noise comes mainly through bone conduction. Such bone conduction explains why we hardly recognize a recording of our speech.
Many of the low-frequency tones which seem to us to give our voices resonance and power are conducted to our ears through the skull; in a recording they are missing, and so our voices often strike us as thin and weak.
Perhaps hearing will atrophy in a civilization where, increasingly, to much is going on. As a result of this overload, we learn to ignore most of the sound around us, and miss much that could give us pleasure and information. Too bad- because there is a wisdom in hearing which we need.