Join us today as we answer the question: what is sound? We’ll go on a journey of sound, together. We’ll shrink down to microscopic levels—200 times smaller than a grain of sand—to follow the path that sound takes.
Imagine that you’ve been shrunk down to a microscopic size. You’re transported to a dark, wet place just sort of floating around. There’s some other stuff floating around you, and with your special glasses you can see that they’re elements: some oxygen here, some nitrogen there.
Then something starts to…change. You start moving in one direction. And it’s not just you: so are all of these elements that you were floating around with. You fly around a few corners, through some tunnels, where are you?
You keep moving. Then you start to notice there’s some shaking. It’s not an earthquake, no; it’s much more organized than that. And all of a sudden you’re not just floating anymore: you’re bumping around. Some oxygen comes from the left, nitrogen from the right, carbon and other stuff here and there.
Turns out, you’ve hit the vocal chords.
It’s the vocal cords where speech really starts. They’re muscles in someone’s throat that are controlled by the brain and designed to precisely vibrate at certain frequencies.
At this stage, the sound is a vibration.
And you start to move at a certain frequency. Back, and forth; back, and forth. There’s a pattern to it, and if you had a stopwatch you’d be able to tell that you’re going back and forth a few hundred—maybe a few thousand—times every second.
But you don’t have time to count, because you start to see a light up above. It’s the end of a tunnel: you’re nearing the mouth.
And then you’re surrounded by light. And so much more than light: the oxygen and nitrogen that kept you company just a second before are now joined by so many other things. You bounce into some dust, and the dust bounces off of you. Then the dust bounces into something else in the air, and it bounces off of something else. A chain reaction. Vibrations are going off in every direction, some fast and some slow; in front of you, behind you, all around you.
There’s a whole lot of bouncing going on, and each time you hit something new it bounces at the same frequency you do.
Where are you going?
You think for a second, as you’re there bouncing through the open air. But quick—there’s not much time left. You see a massive object approaching. Will you hit it? Not yet! But you find yourself headed straight into a black pit. One second you’re in the sun, and the next fraction of a second it starts to get darker and darker and darker until.
Boom. You stop. Well, kind of. It’s like you’ve ran into a trampoline. You’re sort of caught by this massive, stretchy, wall. And in another fraction of a second it moves forward at the same frequency you had been bouncing around through the air.
The vibration pushes against the ear drum.
You’ve reached the ear drum.
If you were a normal piece of dust you wouldn’t be able to go any further, because the ear drum makes an airtight seal. But since you’re special, you transport yourself straight through the ear drum. You end up in a faintly lit chamber and feel the air convulsing all around you. You think of your headlamp for the first time, and turn it on. And you look around.
They’re like the pistons of an old steam locomotive: back and forth and back and forth. One connects to the next and they flex in a glorious unison.
The ear drum’s movement has caused the bones to move.
They’re the ossicles. The smallest bones in the body! The three of them—the hammer, anvil, and stirrup—are there and you grab on and climb along. From one to the next you feel them move, to and fro. They move with the same energy that you had vibrating through the air.
And you move on forward until you’ve reached another wall: it’s the oval window,. It looks much like the ear drum, except it’s much smaller and much thinner. The stirrup pushes up against it, and they vibrate in sync. And you vibrate through it just like you did the ear drum.
But wait, what is this? You’re on the other side, and you’re not surrounded by oxygen any more—you’ve plunged into a liquid.
Welcome to the cochlea.
The moving bones have turned back into vibrations—through liquid, this time.
The liquid is vibrating, like the air was. Back and forth, again, back and forth.
And as you flow through these vibrations you look down. Or up? It’s not clear. But what is clear is that you’re moving in one direction, and you’re slowing down. It seemed like everything was moving so fast at the beginning, and it was: the fast vibrations were high-frequency sounds. But now those ones have fallen off, and so too do you feel yourself falling off.
Where are you going? You look down and your headlamp shows a massive floor that’s vibrating every bit as fast as you are. You swim towards it. This tissue that you’ve found, it’s called the tectorial membrane. You climb around it and on the other side find what look like tiny hairs. You’re still shaking around, so to steady yourself you reach out—you grab one of the hair cells and it starts to move with you.
The vibrations have turned into electrical impulses.
And wham! It’s like you’re transported into a digital world. No longer are you bouncing around objects, now it feels like you’re consumed with energy and everything around you is glowing.
Welcome to the auditory nerve. Zoom, you zoom along in one direction and it seems like almost as soon as you’ve started, you’ve ended.
The electrical impulses have turned into hearing.
You’re in the brain, and you don’t quite know what to make of it. Scientists still today don’t know how exactly the brain turns electrical impulses into the sense of hearing.
So you look around and see all sorts of different explosions or flashes and you’re feeling transported into a magical world—a bigger world—that would rival the best fireworks show you’ve ever seen. You’re starting to get bigger. You start to fill out your surroundings, becoming a brain—a head—a body. You are a body, you’re a person, and you’re you: before you were shrunk down.
And you finally realize what all the vibrating and bouncing and lights were: they were sound.
And you hear your name, as if for the first time.
Even though this seems like a lot of work, sound moves fast. So fast, in fact, that in the time it took to read this story a sound could have traveled around the Earth—twice.
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