(angelic music) - The human voice is an absolutely incredible thing.

Like we take these mouth sounds, and combine them into words and sentences, poems, songs, giving them meaning and emotion and power.

I mean, that's amazing.

It kinda makes you sit back and say... (kazoo buzzing) I built these things for like $5, and they can talk too.

Well, they can make vowels.

They demonstrate something that kinda blew my mind when it clicked for me.

Human language is this absolutely complex and profound and artistic thing.

But at its core, it's really just sounds.

And that means we can describe language with physics.

Every spoken language on earth has one thing in common, vowels.

Why does every language use vowels?

Well, today we're gonna unlock this secret of language, why vowels are at the core of every syllable, and probably the first word you ever spoke.

How these vowel sounds are literally built into your body.

And we're gonna do that using physics.

Hey, smart people, Joe here.

This is the Science of Vowels.

(playful music) Now, it's impossible to cover all of linguistics, and how we make the mouth noises we call language in one video.

But let's cover some basics real quick.

Every language is built mainly out of two types of sounds called vowels and consonants.

You make consonants by bringing together two parts of your mouth or throat, like P. Puh, puh, puh.

You bring your lips together and block the air for a second.

Perfect.

S. (hissing) You bring your teeth together while forcing air out, super.

T, tuh, tuh, tuh, that's your tongue tapping on the roof of your mouth, terrific.

Psst, you wanna know a secret?

If you put those sounds together, you make the only word in the Oxford English Dictionary with no vowels, psst.

Now, some consonants you can actually make without using your vocal chords down here.

Ch, cuh, tuh, puh.

But to make a vowel, you have to engage your vocal chords.

I mean, just try.

A, E, I, O, U.

Your vocal chords are vibrating for all of those.

The word vowel actually comes from the Latin word for vocal.

So everyone's taught that there are five vowels in English.

But that's only true if you're just talking about the alphabet.

All of these letters wear multiple hats.

So English actually ends up having about 12 vowel sounds, depending on your dialect.

And 12 is kind of a lot as languages go.

Spanish only has the basic five, which is actually pretty average.

But Danish has like 30 or 40 vowel sounds, which is why anytime I've ever said a Danish name on this channel, it has not gone well.

So every language is a combination of a finite list of possible mouth noises, which are summarized in the international phonetic alphabet.

And within that, every single possible vowel sound is mapped out here.

This is a really cool chart because it actually tells you how vowels are made.

Over on the bottom left, like, ah, you make that sound with your mouth open.

And you can feel your tongue is sort of toward the front of your mouth.

On the top right, you have sounds that are made with the mouth more closed, and the tongue pushed up toward the back of the mouth, like ooh.

Now, unless you read dictionaries for fun, most of those symbols probably look pretty confusing.

So let's really unpack this for a second.

So I can go from a like in May to ah, like in Mama or "Hey brah."

just by changing the shape of my mouth.

Check it out.

(vocalizing) And I can go from E like in feet to ooh like in boot by just moving my tongue back.

(vocalizing) I feel like a human didgeridoo.

And the almighty schwa, well, that's smack dab in the middle, the most neutral mouth and tongue position, the chillest vowel sound of them all.

Uh.

But basically all possible vowel sounds exist on this spectrum, and you can slide through all of them just by changing the position of your mouth, your tongue, your lips.

This vowel map is also why people argue whether Y and even W are sometimes vowels because the sounds they make fit on this chart.

I mean, why?

Why.

Why, those are vowel sounds.

So how do your voice and mouth parts actually create all these different vowels?

That is where the insanely cool physics comes in, because this is a science channel, not a language channel.

So it's probably time we get to the science.

Okay, so this is your vocal tract.

You can think of it as just a tube open on one end and there's stuff down here that makes noise.

If you had to compare your vocal track to an instrument you might pick a trombone.

(trombone tooting) Warning, potentially uncomfortable image of human anatomy coming.

Don't say I didn't warn you.

These are human vocal chords or vocal folds.

When you speak, they vibrate, and by using muscles to lengthen or shorten them as they vibrate they produce lower or higher pitches.

Just how changing the length of a string on a guitar changes the sound.

(guitar jamming) (bomb exploding) When your vocal chords vibrate they don't produce a single tone or frequency.

They produce a bunch of different frequencies and those aren't random.

Say you're singing a middle C. (piano ringing) You're creating a base tone or fundamental frequency at about 262 hertz because your vocal chords are vibrating back and forth 262 times a second.

But your vocal chords are also producing a bunch of little vibrations on top of that big vibration of the fundamental frequency.

(vocalizing) These are known as harmonics.

I really should not sing on camera.

Let's not do that again.

If we just look at the mix of frequencies made right at your vocal chords, it looks like this.

It's got that fundamental base frequency down here with lots of harmonics up here, but it's just buzzy noise.

And obviously this is not what your voice actually sounds like because something happens in between your vocal chords and someone hearing your voice.

All this stuff.

Now obviously shouting down a tunnel is gonna sound different than shouting inside the open.

Sound bounces around and stuff but there's something more going on here.

Your vocal tract is a very special kind of sound filter and the reason for that is thanks to resonance.

Have you ever blown across the top of a bottle?

Sort of whistles, right?

(bottle whistling) And if you blow across the same bottle with some liquid in it, it makes a different whistle.

(bottle whistling) That's because for a tube with one hole at one end which your voice basically is, the length of it, the space inside, the shape of that space allows certain frequencies to be heard over the others.

Those frequencies get amped up.

That's resonance.

This is how each tube in a pipe organ works.

It's how Lizzo's flute works.

It's how these hilarious whistles work.

(whistle sliding) This one's shaped like a wiener dog.

(air swooshing) (glass crashing) (cat meowing) Your vocal tract is just an open-ended tube too, so it has resonant frequencies.

And whenever you vibrate your vocal chords all this vocal tract stuff filters the sound.

So some of the resonating frequencies stand out louder than all the others.

These amplified frequencies are called formants.

Now, people with bigger bodies and heads have bigger voice tubes.

So the sounds that resonate are lower than people with smaller bodies and tiny heads.

Professional singers train to lengthen their vocal tract to create richer, deeper sounds.

And it's also why your voice sounds so weird when your nose is stuffed up.

I mean part of your resonance tube is blocked.

And we can change which frequencies stand out as we change the shape of our vocal tract by moving our tongue, shaping our lips, opening and closing our jaws.

I mean, I'm doing it right now.

We can change which formants get amped up.

And here's the big mind blowing secret.

This is how vowels are formed.

Vowels are made of physics.

For instance, if you say (vocalizing) your jaw is relatively closed.

Your tongue is high up in your mouth.

In this position there's more space in your throat.

So long wavelengths have room to resonate.

And we see this lower frequency formant here.

Also, when you say E, the front of your tongue is creating a tight space for the sound to pass through.

So only high frequencies can resonate here, and we get a high second formant.

We can do this with any vowel shape.

If you say, ah, well, there's not as much space in the back so only short wavelength resonate there and you get a higher frequency first peak.

But up here, ah, your tongue is flat there's more room than E. So longer frequencies can resonate and you get a lower second formant.

These two bumps, these two frequencies that are amplified by resonance, that's all a vowel is.

Whatever these two lower peaks are, whatever pair of resonant frequencies some given mouth shape amps up, that's what we hear when we hear vowels.

That is so weird.

And these aren't the only two formants your voice makes.

These higher ones are what makes your voice sound like you and not someone else.

But given just those two peaks we can pretty much tell apart every possible vowel sound.

(kazoo buzzing) And that is why these things sound like vowels.

You know, for any one of these the white tube is more open than this black part.

So they're just different length resonators with different shapes.

Like this one makes the sound ah.

It basically goes from small to big, which is not that much different than how your mouth and tongue position are shaped when you make the vowel sound ah.

Or this one, it makes the vowel sound ooh.

And if you feel and think about for a minute what your vocal tract is shaped like, it's not that different.

It's small, big, small, big, small.

That's all vowels are.

These roughly match how closed and open different parts of your vocal tract are when you make these sounds.

And it's so strange that when we hear certain special pairs of resonant frequencies, just these two certain amped up sound peaks, they sound like vowels.

When you talk, you don't even have to think about this.

Your body just does it.

I cannot be the only one whose mind is blown by this.

This is why a wah wah pedal on the guitar sounds like vowels.

(guitar jamming) The electronics in the pedal are boosting certain frequencies, basically creating different combinations of formants that to our ear sound like vowels.

(imitating guitar) Hm, who needs a guitar?

So if talking just requires this simple tube that resonates in weird ways, why don't any other animals talk like us?

I mean, especially primates, right?

Since they're so similar, they've got mouths and tongues.

They can move 'em around.

Well, many primates actually do have all the machinery to make some of the same vowels that we do.

And some of them even do produce vowels.

I mean gorillas, they can make oohs and ahs like (imitating gorilla).

I'm pretty sure they actually say that.

There's even these baboons that can combine two vowels into a call that kind of sounds like wahoo.

(baboon vocalizing) They do it better.

Parrots and songbirds also use their mouths and tongues a lot like we do to create vowels and even combine them to make different calls.

(parrot cawing) But a lot of our ability to make and understand language has to do more with the way our brains are set up to interpret these sounds.

It's not just about making sounds.

And as far as we can tell other animals' brains just aren't wired to use vowels the same way that we do.

I love that even though we have these advanced brains wired to create amazing things like conversations and sonnets and constitutions out of language, at the heart of it there's this really simple and beautiful bit of physics.

I wanna leave you with one thing to think about.

In almost every language, some of the most special words are built almost from pure vowel physics.

Some of the first vowels babies learn to make are ah and uh type sounds because that's what comes out when your mouth just hangs open.

Add a simple consonant sound to those and you get words like Mama, Papa, Dada and baba, words that are used for parents and caregivers in languages all over the world.

That's really special and it's built into us all thanks to physics.