Articulatory Phonetics 101: Airstream Mechanism

This is Part 9 of a series covering the basics of articulatory phonetics, the study of how humans physically produce speech sounds. For the full list of posts, see the Articulatory Phonetics 101 Index.

There will eventually be a video for this post, once I figure out how to produce the videos in a way that isn’t terrible.

Cast your mind back to the first post in this series, where I said…

The physical production of a speech sound begins with an intake of breath.

Well… I lied.

You may have heard of the click consonants of languages like !Xhosa, or maybe the ejective consonants of Georgian, or the implosive consonants of Sindhi.

With clicks, ejectives and implosives, the air flows differently through the vocal tract. These consonants have a different airstream mechanism.

With all the consonants we’ve been studying, all the consonants of English, the airflow starts with increased air pressure in the lungs forcing air outwards through the vocal tract. This is the pulmonic egressive airstream mechanism: it’s the diaphragm and the lungs that drive the movement of the airstream, and the air moves out of the vocal tract. Hence: pulmonic egressive.

Now, let’s look at click consonants. Listen to this sound, and try to copy it.

Got it? This “tsk” sound is probably a sound you’ve made before, but you might not have known that it’s a speech sound in other languages. (I’m assuming you’re primarily an English speaker, of course.) This is the dental click. Let’s examine what happens here.

Now, when you start to make the sound, two things happen simultaneously. The back of your tongue rises up to touch the velum, and at the same time, the tongue tip rises up to touch the back of the teeth. We’ve now formed a closure in not one, but two places: one at the velum, one at the teeth. Now we have a little pocket of air between the palate and the tongue.

Next, what happens is, we lower the tongue just slightly, without moving the two closures at the velum and the teeth, so the air pressure in the air pocket drops.

Then, we release the dental closure, and air rushes into the mouth to fill the low-pressure space. That’s what happens when you produce a click. Because this airstream mechanism is initiated by the tongue, it is a lingual mechanism (from the Latin word “lingua”, meaning “tongue”), and because air is drawn into the vocal tract rather than being forced out of it, we call it an ingressive airstream. The airstream mechanism of click consonants, therefore, is called the lingual ingressive airstream mechanism.

They don’t have to just be dental, either — they can be bilabial, alveolar, alveolar lateral, or palatal as well.

What about ejectives like /k’/?

Well, try it — can you copy the sound you’re hearing?

What is happening here is that first, you’re closing your glottis to form a glottal stop, and at the same time you raise the back of the tongue to touch the velum, forming a velar closure. Now, we have a pocket of air in the pharynx.

You see where this is going!

The next step is to raise the glottis. This increases the air pressure in the air pocket. Then, you release the velar closure, and the compressed air is released out of the vocal tract — pretty forcefully! The airstream is initiated at the glottis and pushes air out of the vocal tract, so we call it the glottalic egressive airstream mechanism. To indicate that a consonant is ejective, we mark it with an apostrophe, as in /k’/.

One more — implosives like /ɓ/.

If you don’t speak a language that has implosives, they might not seem very remarkable to you — like a slightly different-sounding stop. However, about 13% of the world’s languages have contrastive implosive consonants (source: Wikipedia), so we definitely need to examine them closely.

The articulation of an implosive consonant starts like that of an ejective: there’s a closure at the glottis and at the point of articulation — in this case, the lips. Now, we have the same air pocket as we did with ejectives. But this time, instead of raising the glottis, we lower it. This reduces the air pressure in the oral cavity, and then, when we release the bilabial closure (which is how linguists say “opening the mouth”), air is pulled into the vocal tract. This is — you guessed it — the glottalic ingressive airstream mechanism. There are only a limited number of consonants that can be produced this way, and the ones with an IPA symbol are the voiced bilabial /ɓ/, dental /ɗ̪/, alveolar /ɗ/, palatal /ʄ/, velar /ɠ/ and uvular /ʛ/implosives.

These are the four airstream mechanisms found in the world’s languages. We do use other airstream mechanisms to communicate — for example, a gasp is a pulmonic ingressive airstream mechanism — but crucially, these four are the ones we use to produce speech.

And there you have it — a brief introduction to airstream mechanisms. So, we’re finally done with the articulation of consonants, and in the next post, we’ll be looking at vowels. Thanks for reading! See you next time.