vocal tract [G. Ansatzrohr, Vokaltrakt]: the whole of the air passage above the larynx; it can be divided into nasal tract (the air passage above the soft palate, within the nose), and oral tract (the mouth and pharyngeal areas).
An additional distinction is often made in terms of cavities. [Notice that cavity is a polysemous word in English: it refers to a hole in a tooth, but also more generally to a hollow space, as in its use here.] The oral tract can be divided into the oral cavity (the area of the mouth) and the pharyngeal cavity (upward from the larynx to where the nasal tract begins). The pharynx is the tubular cavity which constitutes the throat above the larynx. The nasal tract is also called nasal cavity.
pharynx [G. Rachenraum, Pharynx]: the tubular cavity which constitutes the throat above the larynx. [G. Der schlauchförmige Hohlraum, der den Rachen oberhalb des Kehlkopfes ausmacht.]
The following little picture may help you keep the terminology of tracts and cavities straight. To repeat: the vocal tract (which is the space for airflow above the larynx) consists of the oral tract and the nasal tract. The oral tract, in turn, consists of the oral cavity and the pharyngeal cavity. With this little picture, you may want to go back to Figure 2 and make sure you can approximately identify each tract and each cavity.
Terminology: the space above the larynx:
oral tract nasal tract
oral cavity pharyngeal cavity nasal cavity
(mouth area) (pharynx, up to X) (inside nose, upward from X)
X: point of contact between soft palate and back wall of pharynx.
(see more below on contact between the soft palate and the
back wall of the pharynx.)
3 The larynx: non-speech and speech functions
The non-speech function of the larynx is related to the following 'design-problem' of the way we are made: If both air and food pass through the pharyngeal cavity, how do we achieve that the food ends up in the stomach, and the air in the lungs, rather than the other way around?
The short answer is: The trachea and the esophagus each have a way of closing at the top.
A longer answer follows. In the esophagus, closing off at the top is a 'passive' mechanism. The upper end of the esophagus is built in such a way that it is normally closed. At its upper end, the two opposite walls of the esophagus are up against each other in their normal position. When food is pressed in this direction, it is pressed through this passive closure and enters into the esophagus. When you consciously swallow air and 'burp' it up again, you are moving air below this closure of the esophagus. The burping sound is made when the air is pressed back up out of the esophagus, passes again through this closure at the upper end of the esophagus, and sets the closure in vibration.
The upper end of the trachea is protected by an 'active' mechanism, which is the primary non-speech function of the larynx. Recall that the larynx sits on top of the trachea. When we breathe, the larynx is open, and air passes freely through the larynx into the lungs and back out. When we eat food, the act of swallowing is the act of closing off the trachea and pressing the food into the esophagus. In this process, the larynx is the key player. The larynx closes in two ways to prevent food from entering the trachea. One involves the epiglottis, which you can see in Figure 2. It is a spoon-shaped cartilage (which you see from the side), and you can think of it like the top/cover of a pot, and the larynx as the pot (though a pot with the bottom open in the direction of the trachea). Now you may think that the top comes down to cover the pot and prevent the food from going into the larynx and trachea. And this would be almost correct, except here, the pot (larynx) raises up into its top/cover, so that this epiglottis top/cover passively closes off the top part of the larynx. This 'raising and closing of the pot' is part of the process of swallowing. If you feel your Adam's apple with your finger, and swallow, you can feel how dramatic the raising of the larynx is during swallowing. Try this now. The larynx also closes off in a second way: Internal to the larynx, there are the vocal folds. These are two symmetrical muscular tissues that are connected to the edges of the larynx-"pot". When the two vocal folds come together in the middle, they form a horizontal shield together that covers the entire area of the larynx-"pot", and nothing can pass through. The vocal folds are often also called vocal cords. The vocal cords are also relevant to other bodily processes. For example, when we cough, the vocal cords are first closed and high air-pressure is built up below them by the lungs. Then the vocal cords suddenly open, which releases a puff of cough. Try coughing now, to get a feeling that something is happening in your larynx. Consider also hiccups. These are caused by irritations of the diaphragm at the bottom of the lungs, which, when irritated, cause the lungs to suddenly suck in air very quickly. This sucking in of air, however, is then immediately stopped by a closing of the vocal cords, which produces the 'hick' of the hiccup. Make an artificial hick-up now, to get a sense of how the inward airflow is suddenly stopped in your larynx. These are the vocal folds, or vocal cords.
larynx [G. Kehlkopf, Larynx]: part of the human anatomy on top of the trachea [G. Luftröhre]; the larynx is most noticeable in the adult male neck, where it 'sticks out' as what is known as the Adam's apple [G. Adamsapfel]. The main non-speech function of the larynx is to close off the trachea and the lungs in the process of swallowing food. The speech-functions of the larynx are taken on by the vocal cords (see separate definition), which are inside of the larynx. These functions include the production of the voicing of sounds, and the production of [h] and of the glottal stop [?].
The vocal cords in the larynx are also important in speech production. They produce the voicing of voiced sounds. For example, the initial sound [s] in 'sea', [si], is voiceless, while the initial sound [z] in 'zebra', [zibr´], is voiced. These two sounds [s] and [z] are otherwise articulated identically. The distinction in voicing between them is produced by the vocal folds. Figure 3 shows you schematic pictures of the positions of the vocal folds in the two cases. Imagine you are looking at the larynx from the top. The tip you see at the top of the pictures is the thyroid cartilage that is the Adam's apple, the one that may stick out of the neck a bit. So you see that the larynx-"pot" is not entirely round. In Figure 3 on the left, you see a triangle in the middle of the picture. This is the space between the vocal folds. This space between the vocal folds is also called the glottis. In this picture, imagine that the vocal folds cover the area from the glottis to the edges of the larynx-"pot". The position of the vocal folds in this picture on the left is the position during a voiceless sound like [s]: the vocal folds are far apart, and air can pass through them (through the glottis) freely. In the picture in Figure 3 on the right, you have an indication of what happens during voiced sounds. Here the vocal folds are held together. If nothing else was happening, the larynx would thus be closed. However, as said above, the lungs push up a stream of air during speech. The vocal folds (which are held slack here) start to vibrate in this stream of air. The mechanics of this vibration are similar to when you hold your lips loosely together and blow air out of your mouth forcefully, producing a hammering sound like pppp. Basically, the vibrations arise from the elasticity of the vocal folds (or lips) and from the force of the air pushing against this elastic and loose closure. This vibration of the vocal folds is what we perceive as voicing, such as in the sound [z]. The vibration is schematically drawn in Figure 3 on the right.
Figure 3 From: Péturson/Neppert: Elementarbuch der Phonetik, S.73f
Left: glottis during voiceless