So because I am a Terrible, Horrible, No Good, Very Bad person, this is my first Linguistish post in donkeys years, and for that I profusely apologise. This is actually a revision thing for me, as I have a phonetics exam coming up and need to understand how phonation works, so I thought I’d kill two birds with one stone and everything.
I also have now watched all of Shadowhunters, so I have some reviews of that to do. Hurrah!
On with the post.
Part I: Pho-no-shun
I’m so unoriginal I used a similar pun in my Phonetics 101 post, but whatever. Shoot me.
When we speak, our vocal folds vibrate. Vocal folds are thin sheets of muscle that stretch across the larynx, from the thyroid cartilage at the front (think of a person’s Adam’s apple) to two knobbly cartilages at the back of the larynx called the arytenoid cartilages.
As we saw, many English speech sounds can be either voiced (with vibration of the vocal folds) or voiceless (without vibration). For example, the difference between /b/ and /p/ is purely in the voicing, as they are both bilabial (place of articulation) and plosives (manner of articulation). So, the vocal folds are not always vibrating during speech, but they often are.
How do we make the vocal folds vibrate? This is where theories of phonation come in.
phonation: the process by which we turn moving air from our lungs into vocal fold vibrations
Part II: Take a minute to catch your breath
That’s all very well and good, but how do we get the air moving out of our lungs in the first place? Since this is a Linguistish post, not a…Biologish (?) post, I’ll try to keep it simple.
There are muscles around our ribs called the intercostals. We have two sets – internal, and external. During inspiration (breathing in), the external intercostals and the diaphragm contract, while the chest wall and lungs expand.
(On a side note, when I used to have singing lessons, my teacher always told me to breathe in reverse. Normally, my tummy goes in and my shoulders go up when I breathe in, and my tummy goes out and shoulders relax when I breathe out. She wanted me to do it the other way – let your tummy expand when breathing in so you ‘get more air’ and keep your shoulders down.)
During expiration, the external intercostals and diaphragm relax, and the internal intercostals, chest wall and lungs contract. Because the air is moving from the lungs out of our mouths (for most English speech sounds), they’re called pulmonic egressive sounds.
pulmonic: to do with the lungs
egressive: exiting or leaving
Part III: Myoelastic what now?
Now we’ve reached the point where we have air leaving the lungs and reaching the vocal folds. Things start to get interesting/fun/boring here, depending on your point of view. The myoelastic aerodynamic theory goes as follows:
The vocal folds are elastic, so naturally close. Behind the closure of the vocal folds, air from the lungs builds up. This build up leads to increased air pressure.
The increase in air pressure forces the vocal folds apart, and all the built up air accelerates through the gap. The increase in air speed causes the pressure to drop – this is known as the Bernoulli effect.
Bernoulli effect: as air speed increases, air pressure decreases
A combination of the drop in air pressure and the elasticity of the vocal folds causes them to snap shut. Once more, air builds up behind the closure. This continuous closing, build up, opening and release causes a really, really, quick cycle to happen. Far too fast for us to process, without recorded footage being slowed down.
And, ta dah! That’s how our vocal folds vibrate.