Small Talk 29 - Hearing and Sound
Do you know what's the most popular of the Small Talk essays so far? According to number of page views, it's Small Talk 13 - Smell. By quite a bit, actually. I'm not sure why—maybe it's because people are interested in the senses. So, based on that conjecture, let's talk about another sense: Hearing.
But first, I should correct some errata in the Smell essay, where I said there were five human senses. In a recent conversation with an occupational therapist, I learned that we now recognize eight senses. In addition to the OG five, there are: proprioception (body position in space), vestibular sense (balance), and interoception (sense of your internal body states). What's more, this lovely occupational therapist is married to a professional musician and sound engineer with a degree in digital signal processing. He agreed to help me write this Small Talk, and so you are reading the first such collaboration.
Now, humor me for a second and close your eyes and listen. Try to register all the sounds you hear at this moment. Quite likely, there are many, and they're different pitches, volume, and direction. What's going on exactly? Well, while smell is profoundly chemical, hearing is remarkably... mechanical.
The outer, fleshy part of your ear, called the pinna, is shaped to capture sound waves in your environment. It channels the waves through the narrow ear canal where they collide with the eardrum, a thin membrane about the size of an eraser head. (Not to be confused with Eraserhead, which is more related to the last Small Talk on Surrealism.) The sound waves make the eardrum vibrate, and it passes these vibrations on to three small bones.
Let's pause there. You may remember this from fourth grade science, but it warrants some amazement: we hear because we've evolved three tiny, delicately-connected bones, which serve no purpose but to translate the vibration of sound waves into the cochlea. For the record, the three bones are called: the malleus, the incus, and the stapes. Up to this point, hearing is really just a simple machine.
Inside the cochlea is where things get weird. It's a fascinating organ, about the size of a jelly bean, shaped like the spiral of a snail's shell. (Another example of the Fibonacci sequence in nature.) When the stapes bone pushes against the cochlea, fluid inside the organ ripples in waves. Bundles of hair-like structures, called stereocilia (a good album name) move with the waves, and they transfer that energy as electrochemical signals to the auditory nerve, which connects to the brain. And there, hearing happens. We won't go farther today—except, one more neat detail. Stereocilia conduct different frequencies of sound, depending on where they are in the cochlea. At the base, they detect higher-pitched sounds. The ones farther up the spiral detect lower-pitched sounds.
That's the gist of how hearing works. But it leaves open the important question: What is sound, exactly? You may recall the old philosophical prompt: If a tree falls in a forest where there are no people, does it make a sound? This has always seemed strangely obvious to me, and therefore not really a puzzle—of course the tree makes a sound. Because sound exists independently of humans. I like to think most of us have moved past that degree of solipsism.
Sound is a basic phenomena of physics. A sound, like the toot of a trumpet, creates pressure against the particles of air that surround it. The blast initiates a pattern of alternating higher and lower pressure, or wave, that moves through the air. Sound that vibrates more times per second will have a higher frequency, and therefore a higher pitch. Frequency is measured in hertz (Hz), where one Hz is one cycle of sound per second. Humans can typically hear sounds between 20 Hz and 20,000 Hz. On a piano keyboard, middle C is 262 Hz. It's a very pleasant note. (Some sounds are much less pleasant—but we'll get to that.)
Pitch is different from volume, which is the intensity or amplitude of the sound wave. We might think of it as the force of the pressure that makes the wave. You can play that pleasant C note on a ukelele. Or you can play it on an electric guitar through an amp cranked up to 11. In both cases, the C note is still 262 Hz. But the guitar is playing at much higher decibels (dB), the measure of amplitude (or volume).
Just one more bit of physics: All sounds travel at the same speed when they're in the same medium (like air or water). This is, of course, the speed of sound. Here's a fun thought experiment: If you took a rigid pole that extended the distance to the moon, and pushed a large red button on the surface of the moon, would it happen instantly? That is, did you just do something faster than the speed of light? The answer, of course, is no. The force you put on the rigid pole would travel down the pole at the speed of sound. It would take as long to push the red button as it would for someone on the surface of the moon to hear you playing the C note on a trumpet. (Which doesn't work, unfortunately, because there is no medium between Earth and the Moon to carry the trumpet sound.)
People agree, generally, on what sounds are pleasant and which are annoying. Research suggests people respond positively to the sound of water flowing, to thunder, and to a baby laughing. Just to name a few examples. Most people dislike the sound of a fork scratching glass, a gas-powered leaf blower, and a baby crying. The unpleasant sounds have some things in common—notably, they all include the frequency of about 4,000 Hz. And indeed, audio engineers often remove 4 kHz frequencies from recordings, because they know this range causes 'ear fatigue.' That is, it's annoying.
Most sounds we hear are a blend of frequencies. When you play that C note on a guitar, you'll get the 262 Hz, but the vibration of the string will also produce higher and lower frequencies. These 'overtones' are what make the C note on the guitar sound different from a C note on a trumpet or in a human voice. And human voices are a particularly rich blend of frequencies. Here's a good illustration: older people with hearing loss often can't hear higher frequencies, and so they struggle particularly with women's voices—which usually have higher-pitch overtones. This is why grandpa always says 'Huh?' to grandma when she asks a question from the kitchen.
Many non-human animals have a different sense of hearing. Bats produce and hear ultrasonic (above 20,000 Hz) sounds for echolocation. Elephants rumble at low frequency pitches, below 20 Hz, to communicate across hundreds of miles. Dogs typically hear much higher frequencies, which is why a dog whistle works. But dogs and other mammals share a basic ear anatomy with humans—theirs is just refined in ways that accommodate different kinds of hearing.
If you think the world is getting noisier, you're right. Just 250 years ago, at the founding of the United States, the world was remarkably quiet. There were no cars, trains, planes, steam-powered factories, air conditioners, data center hum, or those ubiquitous gas-powered leaf blowers. It's nice to think about what it must have been like taking a walk through the countryside, with only the sound of birds, crickets, and the wind.
Nevertheless, noise complaints are about as old as history. In the Epic of Gilgamesh, a god vows to exterminate mankind because human racket disturbed his sleep. Since then it's been one long struggle for quiet. In 1972, Richard Nixon of all people authorized the Environmental Protection Agency to enact noise pollution controls. Not long after, the Reagan administration (shocking, I know) shut it down. And life keeps getting louder.
Today in the upper Midwest, the forecast calls for storms. That means we'll have a little relief from the 4kHz sounds and can look forward to some pleasing ones—like the rumble of distant thunder, rain falling on the roof, water running into our rain barrels. And we'll be grateful for hearing and all the other senses that enable us to witness this marvelous life.
Have a good one,
Kipling Knox
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Written in collaboration with Al Knox (of The Night Painters). With thanks to Hannah Knox, OT.
Photo credit: Max, © 2026 Haley Salay
