Place your fingers at the centre of your neck so you can feel the outside of your throat. Say something in a whisper, like 'colourless green ideas sleep furiously.' Now, say it again in your normal voice. Do you feel a difference? You should feel a vibration under your hand while speaking in your normal voice that you don't feel while whispering. What you feel is vocal fold vibration, a.k.a. movement in the glottis. This vibration helps your voice function and plays an important role in speech.
Definition of the glottis
You know from the test what it feels like when the glottis is moving. But what exactly is the definition of the glottis?
The glottis is the part of the larynx that contains the vocal folds.
More specifically, the glottis includes the vocal folds and the space between them, called the rima glottidis.
The vocal folds make up the tissue membrane responsible for voicing in speech.
The rima glottidis is the space between the vocal folds.
The vocal folds are often referred to as the vocal cords. The more current and accurate term is vocal folds. If you come across the terms vocal folds and vocal cords, though, know that they mean the same thing!
If you were to put a tiny camera in your throat, you would be able to see the parts of the glottis. The vocal folds look like two thin layers of tissue next to each other. When the glottis is open, the rima glottidis looks like a V-shaped space between the vocal folds.
Fig. 1 - The glottis is visible when looking at the larynx from above. This drawing shows the glottis in the closed position.
The word glottis comes from the Greek glōssa, meaning tongue. The root appears in other words, too: a polyglot is a person who speaks multiple languages, and a glossary is a bank of words.
Location of the glottis
The glottis is located at the centre of the larynx.
The larynx is an organ made of bone and cartilage located in the center of the throat and contains the glottis.
The larynx is more commonly known as the voice box. It connects the top part of your throat to your lungs, allowing you to breathe, and it houses your vocal folds.
Fig. 2 - The larynx connects the vocal tract to the lungs and protects the vocal folds.
The front of the larynx is visible outside your body as the "Adam's apple."
Glottis vs. epiglottis
The term glottis sounds similar to another structure in the larynx: the epiglottis.
The epiglottis is a piece of cartilage attached to the base of the tongue that protects the windpipe when swallowing.
The Greek root epi- means above or on top of. The epiglottis, then, is literally on top of the glottis. When you swallow, the epiglottis flaps over the glottis and the rest of the larynx to keep any food or drink from entering your windpipe. It doesn't play a role in speech production, but it's a critical structure!
The function of the glottis
What is the glottis and how does this weird, fleshy structure work? As discussed earlier, the glottis controls the flow of air in and out of the lungs, as well as producing sound during speech and voice production. Let's look at how that is achieved.
States of the Glottis
The state of the glottis refers to the position of the vocal folds and the rima glottidis.
Fig. 3 - The states of the glottis from left to right: closed, creaky, whispering, modal, breathy, and voiceless.
The relative tension and narrowness of the glottis characterize certain types of voicing. You'll see more details on that later. In the meantime, the three main states of the glottis to remember are open, closed, and in vibration.
The glottis is open in its resting state. When you breathe normally or produce voiceless consonants (like f, p, and k), the glottis is in the open position. In this state, the vocal folds are spread out and the rima glottidis looks like a wide V.
The closed glottis completely stops the airflow between your lungs and your vocal tract. The tension you feel in your throat when you hold your breath is your throat muscles holding the vocal folds closed. In the closed position, the rima glottidis is not visible at all.
When the glottis is in vibration, air passes through it and makes the vocal folds buzz. Your glottis is in this state when you're talking, singing, or producing voiced consonants (like v, b, and g).
You can test whether a consonant is voiced or voiceless with the same trick you used at the beginning of the explanation. If you feel a vibration in your throat while producing the consonant, it's voiced!
The Glottal Stop
Briefly closing off the glottis while speaking produces a glottal stop. A glottal stop is not a phoneme in English (meaning that two different words can't be distinguished just because one has a glottal stop), but it does appear in English. Say "uh-oh" to yourself and you'll hear two glottal stops.
Here's a question to consider: is it possible to produce a voiced glottal stop? Why or why not? You can find the answer at the end of the explanation!
Vocal Fold Vibration
As you've already seen, the vibration of the vocal folds provides the sound source for your voice. But what makes the vocal folds vibrate? The process is easiest to understand as a series of steps.
- The throat muscles lightly hold the glottis closed.
- Air pressure from the lungs builds up underneath the closed glottis.
- When enough pressure has built up, the vocal folds burst open and release a small amount of air.
- The pressure from the throat muscles pushes the vocal folds back together.
Of course, once the glottis is closed, air pressure from the lungs builds up again, repeating the entire process. The cycle repeats so quickly that it creates a wave of air pressure and a buzzing sound. The pressure wave travels through your vocal tract and produces the sound of your voice.
The number of times the cycle repeats itself per second determines the fundamental frequency of your voice. The fundamental frequency is measured with the unit Hertz (Hz), which means cycles per second.
Tuned to the modern Western scale, the A string on a violin has a fundamental frequency of 440 Hz. If you sing the same note, your vocal folds open and close 440 times every second.
The role of the glottis
The glottis plays an important role in language because it provides a wide range of possible vowels and consonants. In addition, the glottis helps to characterize the quality and tone of your voice.
Three specific states of vocal fold vibration define three types of voicing: modal voice, creaky voice, and breathy voice.
Modal Voice
Modal voicing is the "normal" state of the glottis during voicing. The vocal folds are lightly held together and open at a narrow angle when forced open by air pressure. During modal voicing, the rima glottidis looks like a thin V.
Creaky Voice
You may have heard of a speaking style called "vocal fry." Believe it or not, the more scientific term for vocal fry is "creaky voice."
When you speak in a creaky voice, your throat muscles place more pressure on your vocal folds. The cycle of vocal fold vibration still takes place, but the vocal folds never completely separate from one another. The vibration is much slower (and the frequency is lower) as a result.
If you're wondering what creaky voice sounds like, think of the voice of a distinguished old man, like Gandalf. This sound from a male voice is often considered wise and dignified; the same sound from a female voice is often stigmatized as uneducated and annoying.
Breathy Voice
Breathy voice is essentially the opposite of creaky voice. When you speak in a breathy voice, your throat muscles apply less pressure to your vocal folds. The vocal folds are spread further out when the glottis is open and are never allowed to close completely. The result is the sound of an extended sigh.
For an example of breathy voice, think about singing a lullaby or speaking quietly without fully whispering.
Even though other stops can be both voiced and voiceless, it is not possible to produce a voiced glottal stop. During a glottal stop, the vocal folds are held completely closed. If they're closed, they can't vibrate!
Glottis - Key takeaways
- The glottis is the part of the larynx that contains the vocal folds.
- The glottis is located at the center of the larynx.
- The epiglottis is a piece of cartilage on top of the glottis that protects the glottis while swallowing.
- The three most distinct states of the glottis are closed, open, and in vibration.
- Three specific states of vocal fold vibration define three types of voicing: modal voice, creaky voice, and breathy voice.
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