This is Part 2 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.
In the last video we looked very briefly and very broadly at breath and the vocal tract. In this video, we’re going to zoom into one very specific and very important part of the vocal tract: the vocal folds.
The Vocal Folds
The vocal folds, perhaps better known as the vocal cords, are the part of the vocal tract that vibrates to produce pitch.
When we sing, it is the frequency of the vocal folds’ vibration that determines whether we are singing high or low.
When you breathe, the vocal folds separate, or abduct. When you speak or sing, the vocal folds come together, or adduct.
Sometimes, the vocal folds vibrate at a particular frequency. That frequency is the pitch of your voice. If your vocal folds are vibrating slowly, that’s a low pitch, and if they’re vibrating quickly, that’s a high pitch.
By the way, if you’re curious what the vocal folds really look like, take a deep breath and google “laryngoscopy”.
Voicing and Phonation
Given this tidbit of information, you might assume that the vocal folds are always vibrating when we speak, but that is not at all the case.
Try this little experiment: place the back of your hand against your throat, and make a hissing sound: “ssssssss”.
Did you feel any vibration? Probably not.
Now say “see” with a very exaggerated hissing sound at the beginning: “sssssssee”.
You should be able to feel the difference there — your vocal folds are not vibrating during the “ssssss” at the beginning, but they are vibrating during the “ee”.
Okay — now try this again, except this time, say “zzzzzzzz”, as if you’re mimicking a bee buzzing.
Do you feel your vocal folds vibrating through the “zzzzzz” this time?
This is the difference between the [s] and [z] sounds: the vocal folds are not vibrating during a [s] sound, but they are during a [z] sound. [s] is what we call a voiceless sound, while [z] is what we call a voiced sound.
In fact, if you hold the back of your hand against your throat and you alternate between “ssssss” and “zzzzzz”, you’ll find that the two sounds are otherwise produced in an identical manner.
The only difference is that during “zzzzzz” the vocal folds are vibrating, but during “ssssss”, they are not. This distinction between voiced and voiceless speech sounds is known as voicing or phonation.
When we describe speech sounds, especially consonants, it’s important to know whether the sounds are voiced or voiceless.
Now, the vibration of the vocal folds is just one way in which the vocal tract can shape airflow to form speech sounds. In the next few videos in this series, we’ll look at perhaps the most critical element of the vocal tract for our purposes, the oral and nasal cavities — and learn about how the mouth and tongue help us to speak.