What is phonetics?

Phonetics, the study of speech sounds and their physiological production and acoustic qualities. It deals with the configurations of the vocal tract used to produce speech sounds (articulatory phonetics), the acoustic properties of speech sounds (acoustic phonetics), and the manner of combining sounds so as to make syllables, words, and sentences (linguistic phonetics).

 

Articulatory phonetics

The traditional method of describing speech sounds is in terms of the movements of the vocal organs that produce them. The main structures that are important in the production of speech are the lungs and the respiratory system, together with the vocal organs shown in Figure 1. The airstream from the lungs passes between the vocal cords, which are two small muscular folds located in the larynx at the top of the windpipe. The space between the vocal cords is known as the glottis. If the vocal cords are apart, as they are normally when breathing out, the air from the lungs will have a relatively free passage into the pharynx (see Figure 1) and the mouth. But if the vocal cords are adjusted so that there is a narrow passage between them, the airstream will cause them to be sucked together. As soon as they are together there will be no flow of air, and the pressure below them will be built up until they are blown apart again. The flow of air between them will then cause them to be sucked together again, and the vibratory cycle will continue. Sounds produced when the vocal cords are vibrating are said to be voiced, as opposed to those in which the vocal cords are apart, which are said to be voiceless.

The air passages above the vocal cords are known collectively as the vocal tract. For phonetic purposes they may be divided into the oral tract within the mouth and the pharynx, and the nasal tract within the nose. Many speech sounds are characterized by movements of the lower articulators—i.e., the tongue or the lower lip—toward the upper articulators within the oral tract. The upper surface includes several important structures from the point of view of speech production, such as the upper lip and the upper teeth; Figure 1 illustrates most of the terms that are commonly used. The alveolar ridge is a small protuberance just behind the upper front teeth that can easily be felt with the tongue. The major part of the roof of the mouth is formed by the hard palate in the front, and the soft palate or velum at the back. The soft palate is a muscular flap that can be raised so as to shut off the nasal tract and prevent air from going out through the nose. When it is raised so that the soft palate is pressed against the back wall of the pharynx there is said to be a velic closure. At the lower end of the soft palate is a small hanging appendage known as the uvula.

As may be seen from Figure 1, there are also specific names for different parts of the tongue. The tip and blade are the most mobile parts. Behind the blade is the so-called front of the tongue; it is actually the forward part of the body of the tongue and lies underneath the hard palate when the tongue is at rest. The remainder of the body of the tongue may be divided into the centre, which is partly beneath the hard palate and partly beneath the soft palate; the back, which is beneath the soft palate; and the root, which is opposite the back wall of the pharynx.

 The major division in speech sounds is that between vowels and consonants. Phoneticians have found it difficult to give a precise definition of the articulatory distinction between these two classes of sounds. Most authorities would agree that a vowel is a sound that is produced without any major constrictions in the vocal tract, so that there is a relatively free passage for the air. It is also syllabic. This description is unsatisfactory in that no adequate definition of the notion syllabic has yet been formulated.

Consonants

In the formation of consonants, the airstream through the vocal tract is obstructed in some way. Consonants can be classified according to the place and manner of this obstruction. Some of the possible places of articulation are indicated by the arrows going from one of the lower articulators to one of the upper articulators in Figure 1. The principal terms that are required in the description of English articulation, and the structures of the vocal tract that they involve are: bilabial, the two lips; dental, tongue tip or blade and the upper front teeth; alveolar, tongue tip or blade and the teeth ridge; retroflex, tongue tip and the back part of the teeth ridge; palato-alveolar, tongue blade and the back part of the teeth ridge; palatal, front of tongue and hard palate; and velar, back of tongue and soft palate. The additional places of articulation shown in Figure 1 are required in the description of other languages. Note that the terms for the various places of articulation denote both the portion of the lower articulators (i.e., lower lip and tongue) and the portion of the upper articulatory structures that are involved. Thus velar denotes a sound in which the back of the tongue and the soft palate are involved, and retroflex implies a sound involving the tip of the tongue and the back part of the alveolar ridge. If it is necessary to distinguish between sounds made with the tip of the tongue and those made with the blade, the terms apical (tip) and laminal (blade) may be used.

 

To summarize, a consonant may be described by reference to seven factors: (1) state of the glottis, (2) secondary articulation (if any), (3) place of articulation, (4) type of airstream, (5) central or lateral articulation, (6) velic closure—oral or nasal, and (7) manner of articulation. Thus the consonant at the beginning of the word swim is a (1) voiceless, (2) labialized, (3) alveolar, (4) pulmonic, (5) central, (6) oral, (7) fricative. Unless a specific statement is made to the contrary, consonants are usually presumed to have a pulmonic airstream and no secondary articulation, and it is also assumed that they are not laterals or nasals. Consequently, points 2, 4, 5, and 6 are often disregarded and a three-term description—e.g., voiceless alveolar fricative is sufficient.

 

Vowels

tongue position for vowel sounds

Vowels traditionally have been specified in terms of the position of the highest point of the tongue and the position of the lips. Figure 2 shows these positions for eight different vowels. The highest point of the tongue is in the front of the mouth for the vowels in heed, hid, head, and had. Accordingly, these vowels are classified as front vowels, whereas the vowels in hod, hawed, hood, and who’d are classified as back vowels. The tongue is highest in the vowels in heed and who’d, which are therefore called high, or close, vowels, and lowest in the vowels in had and hod, which are called low, or open, vowels. The height of the tongue for the vowels in the other words is between these two extremes, and they are therefore called midvowels. Lip positions may be described as being rounded, as in who’d, or unrounded or spread, as in heed.

The specification of vowels in terms of the position of the highest point of the tongue is not entirely satisfactory for a number of reasons. In the first place, it disregards the fact that the shape of the tongue as a whole is very different in front vowels and in back vowels. Second, although the height of the tongue in front vowels varies by approximately equal amounts for what are called equidistant steps in vowel quality, this is just not factually true in descriptions of back vowels. Third, the width of the pharynx varies considerably, and to some extent independently of the height of the tongue, in different vowels.

Some authorities use terms such as tense and lax to describe the degree of tension in the tongue muscles, particularly those muscles responsible for the bunching up of the tongue lengthways. Other authorities use the term tense to specify a greater degree of muscular activity, resulting in a greater deformation of the tongue from its neutral position. Tense vowels are longer than the corresponding lax vowels. The vowels in heed and hayed are tense, whereas those in hid and head are lax.

Linguistic phonetics

Phonetics is part of linguistics in that one of the main aims of phonetics is to determine the categories that can be used in explanatory description of languages. One way of looking at the grammar of a language is to consider it to be a set of statements that explains the relation between the meanings of all possible sentences in a language and the sounds of which they are composed. In this view, a grammar may be divided into three parts: the syntactic component, which is a set of rules describing the ways in which words may form sentences; the lexicon, which is a list of all the words and the categories to which they belong; and the phonological component, which is a set of rules that relates phonetic descriptions of sentences to the syntactic and lexical descriptions.