Of Sound Mind

From The Wall Street Journal:

Close your eyes. Listen to what surrounds you. At first, perhaps, the low hum of a space heater—a noise so constant that you only notice it when it stops. Then, a more distant sound—the hiss, click, whoosh of the heating system down the hall as it switches on. After a few moments, you untangle other, slighter sounds. The soft click of typing. Footfalls on an upper floor. The squawk of a blue jay outside. “Sound is all around us—inescapable and invisible,” writes Nina Kraus in “Of Sound Mind: How Our Brain Constructs a Meaningful Sonic World.” Our sense of hearing, she tells us, “is always ‘on.’ ” We ignore it at our peril.

According to Ms. Kraus, a neuroscientist at Northwestern University and the founder of its Brainvolts auditory neuroscience laboratory, most people would choose sight over hearing—they would rather live in silence than in darkness. But, she reminds us, it is sound that provides us with our greatest means of communication. She quotes the author and activist Helen Keller: “Blindness disconnects us from things,” but “deafness disconnects us from people.” Sound is also a source of great nostalgic power. Ms. Kraus writes: “The neighborhood birds, the sounds of leaves rustling, the distant church bell, the abrupt hiss-honk of the city bus’s air brakes and the pick-up basketball game down the street. . . . These all impart a sense of place, a place of belonging.”

We live with constant racket, but we have forgotten how to listen. And yet the part of our brain that is given over to sound—what Ms. Kraus calls the“hearing brain” or “sound mind”—is far bigger and more complex than any of our other sensory equipment. Hearing influences how we feel, how we see, how we move, how we think. It makes us who we are.

“At some point deep in our evolutionary past,” Ms. Kraus explains, natural selection gave us the ability to sense pressure changes with our ears. We developed body parts that “turn the air movement caused by a vibrating guitar string or a spoken word” into something meaningful. Both our ability to move and our ability to hear were developed from similar sources: The deep thrum in our chests when we hear a drumbeat, the innate desire to move to a rhythmic tempo—these echo our earliest development. Sound is motion.

The way by which we convert sound waves into electrical brain signals is indeed unusual: Within the inner ear are tiny hairs in a fluid; when external vibrations enter the ear canal, they agitate the fluid and cause the hair cells to bob up and down. Microscopic projections that perch on top bump and bend, causing porelike channels to open. Chemicals rush into the cells, creating electrical signals that the auditory nerve carry to the brain. Ms. Kraus’s descriptions of the process are rich in metaphorical imagery, giving us the sense that an ear is a cathedral with walls, roof and floor, with fountains of living (electrical) water. But while the science is clear, there remains a magical, awe-inspiring sense of wonder that somehow timing, timbre and pitch can become conversation, lyric and song.

Our comprehension of sound also works in the opposite direction, explains Ms. Kraus: not only from ear to brain, but from brain to ear. A few years ago, a meme on the internet featured someone pronouncing a word. Simple—except no one could agree on the word: It depended on your context. How could this be? Ms. Kraus describes a similar experiment wherein an audio “ba” sound is paired with a video of someone expressing a “fa” sound. Close your eyes, and you hear “ba.” Watch the person in the video, and you hear “fa.” What your brain tells you—in this case, from the sense of sight—influences what you hear. To use another of Ms. Kraus’s examples: During one of her classes she often plays a recording of a sentence that has been so distorted that it sounds like “Darth Vader with a toothache doing a Cookie Monster impersonation during a thunderstorm.” Her students will find the recording incomprehensible—that is, until she plays a clear version of the sentence. “When I play the garbled one again, lightbulbs go off all over the lecture hall. Suddenly that garbled mess is completely understandable to every student. Everyone is amazed at how obvious (in retrospect) the garbled sentence was and can’t believe it was ever challenging. What we know has an enormous influence on what we hear.”

Link to the rest at the Wall Street Journal