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Speech sounds differ from each other in many ways. To describe each sound and see how it is different from the others, we may look at how it is uniquely articulated. For example, what is the position and state of the vocal cords and velum during the sound production? Or, where and how does the airstream come across obstruction? These factors decide the PHONETIC PROPERTIES of each sound.
Place your fingers lightly on your throat. Say "ssssssss" or "fffffff". Then say "zzzzzzz" or "vvvvvv". Do it several times and you will find that in the articulation of the second group of sounds, something vibrates near your throat.
Your throat, or, the LARYNX, is the first point where the airstream initiated from the lung may be modified. It is made up of an opening called GLOTTIS and two VOCAL CORDs (See Fig. 2-2). The vocal cords are two pieces of muscular tissues. In the sound production, the state of the vocal cords determines the VOICING property of the sound. If the vocal cords are widely apart, air can escape freely through the glottis. Sounds produced in this way are VOICELESS because the vocal cords hardly vibrate. However, if the vocal cords are brought close to each other, the passing air will have to force its way through the narrow passage. This makes the cords vibrate, producing a VOICED sound.
Fig. 2-2 States of the vocal cords
With this knowledge of Voicing, we can find out the difference between many pairs of sounds. For example, [b, d, g, v, z] are voiced and [p, t, k, f, s] are voiceless. Voicing is an important feature in a language such as English because the meaning of a word often depends on whether one sound in it is voiced or not. For example, "big" [big] and "pig" [pig] are tremendously different in meaning because the first sound in [big] is voiced and the first sound in [pig] is voiceless.
Now can you tell if the English vowels are voiced or voiceless? Can you find more sounds in English that are in voiced-voiceless pairs? (See Table 2-2) How about the Chinese vowels and consonants. Are they voiced or voiceless?
Say [p, b, m] while putting your fingers on the throat. You will notice that they are all produced by closing the lips. Your fingers on the throat will tell you the difference between [p] and [b] lies in the phonetic property of voicing. But [m] is also voiced because you feel the vibration when you pronounce the prolonged "m-m-m-m". What, then, distinguishes [m] from [b]?
Putting a finger near the nose, say [p, b, m] again. Is there any air let out from the nose for the production of these three sounds? You may find there is air released from the nostril in the production of [m], but no air released in the production of [p, b]. Sounds may be produced with or without nasal airflow—air that runs through the nasal cavity. Sounds such as [m, n, q] are NASAL because during the articulation of them, the air flows through the nose as well as the mouth. Sounds such as [p, b] which let no nasal airflow are ORAL sounds.
Whether the airstream flows out of the mouth or the nose is decided by the position of the velum. The velum functions as a revolving door. When it is raised, the entrance into the nose is cut off. Then the airstream only has one passage to escape—the mouth. Sound thus produced is oral. However, when the velum is lowered, the entrance leading to nose is open, and air can escape both mouth and nose. In this manner, a nasal sound is produced. (See Fig. 2-3)
Fig. 2-3 Positions of the velum
Most of the sounds in both Chinese and English are oral sounds. Both languages have the following nasal sounds: [m, n, q], such as [di:n] "dean", [ti:m] "team", and [riŋ] "ring" in English; [ma] “吗、马、码、骂”, [lin]“拎、林、懔、吝”and [liŋ]“灵、领、令”in Chinese.
By referring to the phonetic property of voicing and nasality, we may describe the sounds [b, d, g] as voiced oral sounds. But still they are different sounds. Then what phonetic properties distinguish [b], [d] and [g] from one another? Now let's try to pronounce the three sounds alternatively.
Every time you try a new sound, you will have to move your lips and tongue so that your oral cavity is reshaped.
When you produce [b], you bring both lips together. Sounds thus produced are called BILABIALS because the place of articulation is between the two lips.
When you pronounce [d], you bring your tip of tongue to the teeth ridge and then let it open. Therefore, it is an ALVEOLAR sound.
To produce [g], you raise the back of the tongue to the soft palate, therefore you are articulating a VELAR sound.
Articulation may also take place at other places:
LABIODENTALs: Sounds produced between the bottom lip and the upper teeth, such as the voiceless [f] in "feel" and voiced [v] in "veil";
INTERDENTALs: Sounds produced at the place between upper teeth and lower teeth, such as voiceless [θ] in "thank" and voiced [ð] in "then";
PALATALs: Sounds produced when the tongue is raised towards the hard palate, such as voiceless [ʃ] in "fish", voiced [ʒ] in "usual" and [j] in "yet";
GLOTTALs: Sounds produced at the glottis by the moving of the vocal cords, such as the voiceless [h] in "house".
Places of articulation is another important factor in the sound production. For example, how are the sound [f] in "fee", [θ] in "thin", [s] in "see' and [ʃ] in "she" different from each other? The table below shows that they differ from each other in the places of articulation.
To see where the places of articulation are in the oral tracts, refer to Fig. 2-1, where each place of articulation is marked with arrows. To figure out the places of articulation for the English consonant sounds, look at Table 2-2 (see 2.4.5).
Task 2-2 Voicing, Nasality and Places of Articulation are important phonetic properties in sound production. Now look at the following pairs of sounds. Can you tell how one sound is different from the other in each pair by referring to the above three phonetic properties?
The above table shows that [t, d] in Pair (1) differ from each other in Voicing; [d, n] in Pair (2) differ from each other in Nasality, [d, b] in (3) differ from each other in Places of articulation. But the sounds in Pair (4)—(6) identify with each other in all the above factors. So, to find out how they are different from each other in articulation, we will have to turn to a new factor. This time we will see how the articulators modify the passing airstream, or, how much obstruction the airstream comes across along the vocal tract. We will study the manner features of the involved articulators, or the MANNERS OF ARTICULATION.
There are a dozen of manner features, we will only refer to the most easily distinctive ones in this chapter. They are STOPs, FRICATIVEs, AFFRICATEs and APPROXIMANTs.
1. Stops
Put a slip of paper before your mouth and try the English sounds [p, b, t, d, k, g]. Do you notice that the paper suddenly flaps when the airstream "rushes" out of your mouth? This happens because in the production of the above sounds, the airstream is completely blocked for a brief period in the oral cavity before it is released. Sounds resulting from such manner of articulation are stops because the airflow is momentarily stopped.
2. Fricatives
Now try the sounds [s, z, f, v, ʃ, ʒ, θ, ð]. This time, instead of flapping, the paper waves slightly. You can feel a continuous weak air current flowing out of the month. So these sounds are articulated in different manners from those of the stops. They are articulated when two articulators move close to each other so that a narrow passage is formed. Since the air has to pass through a narrow passage, the sound produced takes on a feature of friction. Sounds produced with such a manner are the fricatives.
3. Affricates
We can combine the above two manners in the production of sounds. That will be affricates. For example, when we want to articulate [tʃ, dʒ], we start by putting the tip of tongue at the teeth ridge so the airstream is blocked. (It is the same as what we will do for [t, d]). Then, instead of letting the closure released suddenly, we slowly move the tongue back from the alveolar so that a narrow passage is opened. The air will pass through this passage with a friction. So an affricative is the combination of the first step of a stop (forming a closure) and process of articulating a fricative (forming a continuous frication).
4. Approximants
In the articulation of some sounds, such as [j, w, r, l, h], the airstream comes across very weak obstruction in the mouth. Sounds produced in this manner are strongly influenced by the neighboring sounds, and we call them approximants.
With the help of manners of articulation, we can look back upon Task 2-2. Now can you tell in Pair (4)-(6), how each sound is different from the other?
To describe a consonant, or to figure out how one consonant differs from another, we will have to refer to the phonetic properties we discussed in the above sections, they are:
(1) Voicing (voiced or voiceless): the state of the vocal cords in the articulation of sounds;
(2) Nasality (nasal or oral): if the airstream is let out through the nasal cavity or not;
(3) Places of articulation: where the airstream comes across the strongest obstruction;
Table 2-2 The phonetic properties of English consonants
(4) Manners of articulation: to what degree the airstream is impeded.
Table 2-2 summarizes the phonetic properties of the English consonants.