2.3　Speech Organs

Have you ever seen a performance of vocal mimicry? It is incredible that the human body has such a potential in producing sounds. However, the mimicry is an extreme case of sound production. What the mimic expert has produced, such as the plane taking off, the train arriving, the building collapsing, etc, is not human speech sounds. The parts of body he uses to produce sounds, such as hands, chest or knees, are not speech organs. Moreover, the methods he applies to produce sounds, such as clapping his hands, clicking his teeth, or stamping his feet, are not the normal manners we use to articulate speech sounds.

When we are speaking, we make use of a set of organs, such as mouth and nose. The primary function of these organs is eating and breathing, but they are also active in the process of sound production. If any of them is changed in state or position, the passing air will be modified, and the sounds produced thereafter will be different. So, to study speech sounds, we shall start by identifying the SPEECH ORGANs, or the ARTICULATORs. Then we will see the process of articulation and the properties of sounds.

In our daily life, we can feel the movement of our tongue or throat when we are speaking. We cannot see them clearly because they are "hidden" within our bodies. So, to see clearly how those organs work in the production of sounds, we imaginarily crack a head down the middle and draw a picture as shown in Fig. 2-1.

We can compare the human speech organs to a Scotland bagpipe. To produce the musical sounds, the performer will have to blow some air into the bag. Then the stored air is forced out, modified in different ways, and finally let out from different pipes.

When we are speaking, especially if we plan to speak a long sentence. We do the same. We draw in a deep breath so that the air can be stored in the lung. Then we release it into the VOCAL TRACT. The vocal tract can be rapidly reshaped in many different ways, and this will result in different resonating properties. Finally the air is released through the mouth or the nose. The effect of this is to create a variety of different sounds in human speech.

Sounds are different from one another because they take on different properties along the vocal tract. Along this route, the air passes in turn through: (see Fig. 2-1)

a. the GLOTTIS: we normally call it throat. It is the place where the "Adam's Apple" locates. It is the starting point of vocal tract. It is also the first point where the airstream is likely to come across any modification.

b. the PHARYNX: it is like a three way crossroad which allows entrance to either the mouth or the nose.

c. the VELUM: a movable muscle. In sounds articulation, the position of this muscle determines the way the airstream will pass through after it leaves the pharynx.

d. ORAL CAVITY (mouth) or NASAL CAVITY (nose). The airstream may come cross modification of different types in the oral cavity. It is a room where the most articulators co-inhabit, such as the TONGUE, the SOFT PALATE (velum), the HARD PALATE, the TEETH (dents), the TEETH RIDGE (ALVEOLAR RIDGE), and the LIPS (LABIALS).

Some of the articulators are movable, such as the lips, the tongue, the velum and the glottis. So they are active in the sound production. Other articulators are relatively more passive, such as the hard palate.

To fully understand what Fig. 2-1 wants to show, you will have to know some phonetic terms. Most of these terms are derived from Latin and Greek and are difficult to remember. In Table 2-1, we set up a one-to-one correspondence between those terms and the normal names from which they are derived. So in the further reading of this chapter and the following chapter, you may refer to this table whenever necessary.