Larynx

Diagram of the Larynx

As fascinating as it is, examining your Adam's apple in the mirror doesn't tell you much about the anatomy of the larynx. If you want to examine the larynx in greater detail without putting a camera in your throat, you can refer to a handy, labeled diagram. This diagram shows a cross-section of the larynx. The next section details each part of the larynx's anatomy.

Fig. 1 - The larynx is the entire "voice box" and includes the vocal folds.

Structure of the Larynx

As you can see, the larynx is a delicate organ with many small parts. Each part serves a particular purpose.

Epiglottis

The topmost part of the larynx is the epiglottis.

Think of the epiglottis as the "lid" of your larynx. When you swallow, it flaps over the top of your larynx to keep food and drink from entering your windpipe. If you've ever laughed while eating or drinking and been sent into a coughing fit, it's because the epiglottis didn't have time to close off the larynx before anything entered it. This allowed the food or drink to "go down the wrong pipe."

Hyoid Bone

Below the epiglottis is the hyoid bone.

The hyoid bone allows you to change the pitch of your voice. This is explained in the next section.

Thyroid Cartilage

When you look at your Adam's apple, you see your thyroid cartilage.

Think of the thyroid cartilage as a shield. The vocal folds at the center of your larynx are very delicate; the thyroid cartilage shields them from any outside force.

Cricoid Cartilage

Right underneath the thyroid cartilage, you'll find the cricoid cartilage.

Trachea

The trachea is the lowest part of the larynx.

In other words, the trachea is the windpipe. This tube allows you to breathe through your nose and mouth.

Glottis (Vocal Folds)

Finally, the glottis is the part of the larynx with the most significant role in speech production.

The glottis looks like a "V" of very thin tissue. Forcing air through the larynx at a high velocity causes this "V" to vibrate, producing a "voiced" sound.

Fig. 3 - This drawing illustrates the glottis in the open position.

The Function of the Larynx in Sound Production

Two structures in the larynx play a major role in speech production: the vocal folds and the hyoid bone. The vibration of the vocal folds provides the sound source for the voice, and the movement of the hyoid bone helps to change the pitch of the voice.

The Role of the Glottis in Sound Production

As was mentioned earlier, forcing air through the larynx causes the vocal folds to vibrate. When you build up enough air pressure under the vocal folds in the closed position, they briefly flap open, letting out a short burst of air, then snap shut again. Once the vocal folds are closed, air builds up under them again, and the process repeats.

This action is repeated hundreds of times per second. The rapid movement of the vocal folds creates a buzzing sound, which is amplified by the rest of your vocal tract. The resulting sound is the sound of your voice.

The Role of the Hyoid Bone in Sound Production

The hyoid bone plays a less important, but still significant, role in sound production. The hyoid bone can raise and lower itself to change your voice's fundamental frequency, or pitch. How does it do that? Well, when the hyoid bone raises itself, it makes the tube of the vocal tract a bit shorter. When air passes through a shorter tube, it produces a higher pitch (think about the length of a bassoon compared to a piccolo). Conversely, when the hyoid bone lowers itself, it slightly lengthens the rest of the vocal tract, lowering the pitch of your voice. This is one of the functions that allow you to speak at different levels or sing different notes.

The Importance of the Larynx in Sound Production

You know now how the parts of the larynx contribute to sound production. But how does that help people communicate?

To start, voicing is the primary sound source for vowels. You can produce vowel sounds without using your vocal folds (by speaking in a whisper), but that will only get you so far. Producing your vowels using vocal fold vibration allows you to speak loudly and intelligibly.

In addition, voicing potentially doubles the number of consonants available in a language. The sounds [p] and [b] differ only in their voicing: [p] is a voiceless bilabial stop, and [b] is a voiced bilabial stop. This small difference allows words like pat and bat to be recognizable as two different words in English.

Finally, changing the pitch of your voice allows for greater potential communication through intonation. Take these two sentences:

These sentences carry different meanings, but the only difference in how they're produced is the audible pitch contour. In languages that utilize intonation in this way, the pitch contour can distinguish a question from a statement, convey differences in emotion, and produce clearer utterances.

Some languages also utilize pitch contours as phonemes. In these languages, low, mid, and high tone movements can distinguish individual words. Chinese, Thai, and Igbo are some examples of tonal languages.