The first linguist who tried to describe and classify vowels for all languages was D. Jones. He devised the system of 8 Cardinal Vowels. The basis of the system is physiological. Cardinal vowel No. 1 corresponds to the position of the front part of the tongue raised as closed as possible to the palate. The gradual lowering of the tongue to the back lowest position gives another point for cardinal vowel No.5. The lowest front position of the tongue gives the point for cardinal vowel No.4. The upper back limit for the tongue position gives the point for cardinal No.8. These positions for Cardinal vowels were copied from X-ray photographs. The tongue positions between these points were X-rayed and the equidistant points for No.2, 3, 6, 7 were found. The IPA symbols (International Phonetic Alphabet) for the 8 Cardinal Vowels are: 1 -i, 2 - e, 3 - ε, 4 - a, 5 - a:, 6 - , 7 - o, 8 - u.
The system of Cardinal Vowels is an international standard. In spite of the theoretical significance of the Cardinal Vowel system its practical application is limited. In language teaching this system can be learned only by oral instructions from a teacher who knows how to pronounce the Cardinal Vowels.
Russian phoneticians suggest a classification of vowels according to the following principles: 1) stability of articulation; 2) tongue position; 3) lip position; 4) character of the vowel end; 5) length; 6) tenseness.
1. Stability of articulation. This principle is not singled out by British and
American phoneticians. Thus, P. Roach writes: "British English (BBC accent) is
generally described as having short vowels, long vowels and diphthongs". According to Russian scholars vowels are subdivided into: a) monophthongs (the tongue position is stable); b) diphthongs (it changes, that is the tongue moves from one position to another); c) diphthongoids (an intermediate case, when the change in the position is fairly weak).
Diphthongs are defined differently by different authors. A.C. Gimson, for example, distinguishes 20 vocalic phonemes which are made of vowels and vowel
glides. D. Jones defines diphthongs as unisyllabic gliding sounds in the articulation of which the organs of speech start from one position and then elide to another
position. There are two vowels in English [i:, u:] that may have a diphthongal glide where they have full length (be, do), and the tendency for diphthongization is becoming gradually stronger.
2. The position of the tongue. According to the horizontal movement Russian phoneticians distinguish five classes: 1) front; 2) front-retracted; 3) central; 4) back; 5) back-advanced.
British phoneticians do not single out the classes of front-retracted and back-advanced vowels. So both [i:] and [i] are classed as front, and both [u:] and [Y] are classed as back.
The way British and Russian phoneticians approach the vertical movement of the tongue is also slightly different. British scholars distinguish three classes of vowels: high (or close), mid (or half-open) and low (or open) vowels. Russian phoneticians made the classification more detailed distinguishing two subclasses in each class, i.e. broad and narrow variations of the three vertical positions. Consequently, six groups of vowels are distinguished.
English vowels and diphthongs may be placed on the Cardinal Vowel quadrilateral as shown in Figs. 2, 3, 4.
3. Another feature of English vowels is lip position. Traditionally three lip positions are distinguished, that is spread, neutral, rounded. Lip rounding takes place rather due to physiological reasons than to any other. Any back vowel in English is produced with rounded lips, the degree of rounding is different and depends on the height of the raised part of the tongue; the higher it is raised the
more rounded the lips are.
4. Character of the vowel end. This quality depends on the kind of the articulatory transition from a vowel to a consonant. This transition (VC) is very closed in English unlike Russian. As a result all English short vowels are checked when stressed. The degree of checkness may vary and depends on the following consonants (+ voiceless - voiced - sonorant -).
5. We should point out that vowel length or quantity has for a long time been the point of disagreement among phoneticians. It is a common knowledge that a vowel like any sound has physical duration. When sounds are used in connected speech they cannot help being influenced by one another. Duration of a vowel depends on the following factors: 1) its own length; 2) the accent of the syllable in which it occurs; 3) phonetic context; 4) the position in a rhythmic structure; 5) the position in a tone group; 6) the position in an utterance; 7) the tempo of the whole utterance; 8) the type of pronunciation. The problem the analysts are concerned with is whether variations in quantity are meaningful (relevant). Such contrasts are investigated in phonology.
There is one more articulatory characteristic that needs our attention, namely tenseness. It characterizes the state of the organs of speech at the moment of vowel production. Special instrumental analysis shows that historically long vowels are tense while historically short are lax.