What is Phonetics?

Phonetics, branch of linguistics concerned with the production, physical nature, and perception of speech sounds. The main fields of study are experimental phonetics, articulatory phonetics, phonemics, acoustical phonetics, and auditory phonetics. Auditory phonetics is the field involved in determining how speech sounds are perceived by the human ear.

Experimental Phonetics

This is the physical science that collects measurable data about the articulatory, acoustic, and auditory properties of vocal sounds, using instruments such as the kymograph, which traces curves of pressure, and the X ray. The amount of detail in the measurement of vocal sounds is limited only by the precision of the instrument. Differences are found in every vocal sound.

Articulatory Phonetics

This describes speech sounds genetically-that is, with respect to the ways by which the vocal organs modify the air stream in the mouth, nose, and throat in order to produce a sound. All the vocal activities involved in a sound need not be described, but only a selection of them, such as the place and manner of articulation. Phonetic symbols and their articulatory definitions are abbreviated descriptions of these selected activities. The symbols most commonly used is the International Phonetic Alphabet (IPA).

The organs of articulation are either movable or stationary. Movable organs such as lips, jaws, tongue, or vocal chords are called articulators. By means of them a speaker modifies the surge of air from the lungs. Stationary parts include the teeth, the alveolar arch behind them, the hard palate, and the softer velum behind it. Sounds made by touching two articulators-for example, the bilabial p, which requires both lips-or those made by an articulator and a stationary part of the vocal apparatus are named from the organs that make the juncture, which is called the point of articulation. Reference to the tongue, when it is an articulator, is not expressed-for example, the t sound, which is produced by the alveolar arch touched by the tongue, is called alveolar.

The manner of articulation is determined by the way in which the speaker affects the air stream with the movable organs. This action may consist of stopping the air completely (plosive); leaving the nasal passage open during the stopping (nasal); making contact with the tongue but leaving space on either side of it (lateral); making merely a momentary light contact (flap); leaving just enough space to allow a continuing stream of air to produce friction as it passes through (fricative); or permitting the air stream to pass over the center of the tongue without oral friction (vocal). The speaker produces vowels of different quality by varying the position of his or her tongue on its vertical axis (high, mid, low) and on its horizontal axis (front, central, back). The quality of a vowel also depends on whether the speaker keeps the lips rounded or unrounded, keeps the jaws close together or open, or holds the tip of the tongue flat or curled up (retroflex). At the same time the speaker may move the tongue gradually upward and to the front, or upward and to the back, making diphthongal off-glides.

Other modifications may also affect the quality of the sounds. For example, nasals rather than vowels may be made the prominent part of the syllable, and certain typical vowel formations, called semivowels, may be nonsyllabic. The quality of certain sounds is also affected by whether the speaker keeps the speech organs tense or lax. The vocal cords are vibrated to produce sounds that are voiced. Vowels are voiced, and in English, lax consonants are more or less voiced. When the speaker gives a strong puff of air after the contact, this is called aspiration. If the hand is placed before the lips, aspiration may be observed in the ph sound produced at the beginning of the word pie. The accompanying charts of the International Phonetic Alphabet, using standard transcriptions in brackets, presents a schematic description of these activities in English, although not all the modifications are included. An accurate phonetic transcription of all would describe even regional accents.


This is a study of the sounds of speech in their primary function, which is to make vocal signs that refer to different things sound different. The phonemes of a particular language are those minimal distinct units of sound that can distinguish meaning in that language. In English, the p sound is a phoneme because it is the smallest unit of sound that can make a difference of meaning if, for example, it replaces the initial sound of bill, till, or dill, making the word pill. The vowel sound of pill is also a phoneme because its distinctness in sound makes pill, which means one thing, sound different from pal, which means another. Two different sounds, reflecting distinct articulatory activities, may represent two phonemes in one language but only a single phoneme in another. Thus phonetic r and l are distinct phonemes in English, whereas these sounds represent a single phoneme in Japanese, just as ph and p in pie and spy, respectively, represent a single phoneme in English although these sounds are phonetically distinct.

Phonemes are not letters; they refer to the sound of a spoken utterance. For example, flocks and phlox have exactly the same five phonemes. Similarly, bill and Bill are identical phonemically, regardless of the difference in meaning. Each language has its own inventory of phonetic differences that it treats as phonemic-that is, as necessary to distinguish meaning. For practical purposes, the total number of phonemes for a language is the least number of different symbols adequate to make an unambiguous graphic representation of its speech that any native could read if given a sound value for each symbol, and that any foreigner could pronounce correctly if given additional rules covering nondistinctive phonetic variations that the native makes automatically. For convenience, each phoneme of language may be given a symbol.

Acoustical Phonetics

This is the study of speech waves as the output of a resonator-that is, the vocal tract coupled to other sources. Sound waves are closer than articulations to the essence of communication, because the same auditory impression can be produced by a normal articulation and by an entirely different sound apparatus, like that of parrots. A spectrograph may be used to record significant characteristics of speech waves and to determine the effect of articulatory activities. Parts of this record of speech waves can be cut out experimentally and the rest played back as sound in order to determine which features suffice to identify the sounds of a language.