Human speech is the result of a highly complicated series of events. Let us consider the speech chain, which may be diagrammed in simplified form like this:
Speaker's brain
Speaker's vocal tract
Transmission of sounds
Listener's ear
Listener's brain
through air
linguistic
articulatory
acoustic
auditory
linguistic
The formation of the concept takes place in the brain of a speaker. This stage may be called psychological. The message formed within the brain is transmitted along the nervous system to the speech organs. Therefore, we may say that the human brain controls the behaviour of the articulating organs which effects in producing a particular pattern of speech sounds. This second stage may be called physiological. The movements of the speech apparatus disturb the air stream thus producing sound waves. Consequently, the third stage may be called physical or acoustic. Further, any communication requires a listener, as well as a speaker. So the last stages are the reception of the sound waves by the listener's hearing physiological apparatus, the transmission of the spoken message through the nervous system to the brain and the linguistic interpretation of the information conveyed. . The sound phenomena have different aspects:
(a) the articulatory aspect;
(b) the acoustic aspect;
(c) the auditory (perceptive) aspect;
(d) the functional (linguistic) aspect.
Now it is possible to show the correlation between the stages of the speech chain and the aspects of the sound matter.
Articulation comprises all the movements and positions of the speech organs necessary to pronounce a speech sound. According to their main sound-producing functions, the speech organs can be divided into the following four groups:
(1) the power mechanism;
(2) the vibration mechanism;
(3) the resonator mechanism;
(4) the obstruction mechanism.
The functions of the power mechanism consist in the supply of the energy in the form of the air pressure and in regulating the force of the air stream. The power mechanism includes: (1) the diaphragm, (2) the lungs, (3) the bronchi, (4) the windpipe, or trachea. The glottis and the supra-glottal cavities enter into the power mechanism as parts of the respiratory tract. The vibration mechanism consists of the larynx, or voice box, containing the vocal cords. The most important function of the vocal cords is their role in the production of voice. The pharynx, the mouth, and the nasal cavity function as the principal resonators thus constituting the resonator mechanism. The obstruction mechanism (the tongue, the lips, the teeth, and the palate) forms the different types of obstructions.
The acoustic aspect studies sound waves. The basic vibrations of the vocal cords over their whole length produce the fundamental tone of voice. The simultaneous vibrations of each part of the vocal cords produce partial tones (overtones and harmonics). The number of vibrations per second is called frequency. Frequency of basic vibrations of the vocal cords is the fundamental frequency. Fundamental frequency determines the pitch of the voice and forms an acoustic basis of speech melody. Intensity of speech sounds depends on the amplitude of vibration.
The auditory (sound-perception) aspect, on the one hand, is a physiological mechanism. We can perceive sound waves within a range of 16 Hz-20.000 Hz with adifference in 3 Hz. The human ear transforms mechanical vibrations of the air into nervous and transmits them to brain. The listener hears the acoustic features of the fundamental frequency, formant frequency, intensity and duration in terms of perceptible categories of pitch, quality, loudness and length. On the other hand, it is also apsychological mechanism. The point is that repetitions of what might be heard as the same utterance are only coincidentally, if ever, acoustically identical. Phonetic identity is a. theoretical ideal. Phonetic similarity, not phonetic identity, is the criterion with which we operate in the linguistic analysis.
Functional aspect. Phonemes, syllables, stress, and intonation are linguistic phenomena. They constitute meaningful units (morphemes, words, word-forms, utterances). Sounds of speech perform different linguistic functions.
Let's have a look at the correlation of some phonetic terms discussed above.
articulatory characteristics
acoustic properties
auditory(perceptible) qualities
linguistic phenomena
vibration of the vocal cords
fundamental frequency
melody
pitch
different positions and movements of speech organs
formant frequency
quality (timbre)
phoneme
the amplitude of vibrations
intensity
loudness
stress
the quantity of time during which the sound is pronounced
duration
length
tempo, rhythm, pauses
The phonetic system of language is a set of phonetic units arranged in an orderly way to replace each other in a given framework. Phonetics is divided into two major components (or systems): segmental phonetics, which is concerned with individual sounds (i.e. "segments" of speech) and suprasegmental phonetics dealing with the larger units of connected speech: syllables, words, phrases and texts.
1. Segmental units are sounds of speech (vowels and consonants) which form the vocalic and consonantal systems;
2. Suprasegmental, or prosodic, units are syllables, accentual (rhythmic) units, intonation groups, utterances, which form the subsystem of pitch, stress, rhythm, tempo, pauses.
Now we may define phonetics as a branch of linguistics that studies speech sounds in the broad sense, comprising segmental sounds, suprasegmental units and prosodic phenomena (pith, stress, tempo, rhythm, pauses).
Let us consider the four components of the phonetic system of language.
The first and the basic component of the phonetic structure of language is the system of its segmental phonemes existing in the material form of their allophones. The phonemic component has 3 aspects, or manifestations:
1. the system of its phonemes as discrete isolated units;
2. the distribution of the allophones of the phonemes;
3. the methods of joining speech sounds together in words and at their junction, or the methods of effecting VC, CV, CC, and VV transitions.
The second component is the syllabic structure of words. The syllabic structure has two aspects, which are inseparable from each other: syllable formation and syllable division.
The third component is the accentual structure of words as items of vocabulary (i.e. as pronounced in isolation). The accentual structure of words has three aspects: the physical (acoustic) nature of word accent; the position of the accent in disyllabic and polysyllabic words; the degrees of word accent.
The fourth component of the phonetic system is the intonational structure of utterances. The four components of the phonetic system of language (phonemic, syllabic, accentual and intonational) all constitute its pronunciation (in the broad sense of the term).