Talking about vowels requires first to specify their articulatory and acoustic characteristics. Vowels unlike consonants are produced with no obstruction to the stream of air, so on the perception level their integral characteristic is naturally tone, not noise. It would be interesting to know that a minimum vowel system of a language is likely to take the form of
The most important characteristic of the quality of these vowels is that they are acoustically stable. They are known to be entirely different from one another both articulatorily and acoustically. Consequently they may well be said to form boundaries of "phonetic field of vowels" in a modem man's life. Thus they display the highest degree of unlikeness and so maximum of abilities of people as regards to vowels. We could add that the commonest vowel system adds two other vowels to this minimum triangle to give a five vowels system of the type:
In the matter of the English language it would be fair to mention that due to various reasons it has developed a vocalic system of a much larger number of phonemes.
The articulatory classification of vowels
The quality of a vowel is known to be deterined by the size, volume, and shape of the mouth resonator, which are modified by the movement of active speech organs, that is the tongue and the lips. Besides, the particular quality of a vowel can depend on a lot of other articulatory cracteristics:
the relative stability of the tongue
the posItion of the lIps
physical duration of the segment
the force of articulation
the degree of tenseness of speech organs.
So vowel quality could be thought of as a bundle of definite articulatory characteristics which are sometimes intricately interconnected and interdependent. For example, the back position of the tongue causes the lip rounding, the front position of the tongue makes it rise higher in the mouth cavity, the lengthening of a vowel makes the organs of speech tenser at the moment of production and so on. From what we have said it follows that isolation and distinctions of the above-mentioned articulatory features are done only for the sake of analysis with the purpose of describing the vocalic system of the English language.
The analysis of the articulatory constituents of the quality of vowels allowed phoneticians to suggest the criteria which are conceived to be of great importance in classificatory description. First to be concerned here are the following criteria termed:
a) stability of articulation;
b) tongue position;
c) lip position;
d) character of the vowel end;
In the part that follows, each of the above-mentioned principles will be considered from phonological point of view. Stability of articulation specifies the actual position of the articulating organ in the process of the articulation of a vowel. There are two possible varieties:
a) the tongue position is stable;
b) the tongue position changes, that is the tongue moves from one position to another.
In the first case the articulated vowel is relatively pure, in the second case a vowel consists of two clearly perceptible elements. There exists in addition a third variety, an intermediate case, when the change in the tongue position is fairly weak. So according to this principle the English vowels are subdivided into:
Though the interpretation we have just given is an obvious matter for phoneticians it does not mean that this way of seeing the situation is shared by British phoneticians. A.C.Gimson, for example, distinguishes twenty vocalic phonemes which are made of vowels and vowel glides. Seven of them are treated as short phonemes: [e] [ ?] [?] [o] [?] [?] [ ] and thirteen as long ones [a: ] [ o: ] [u:] [ з: ] [і:] [ei] [e?] [ai] [au] [ou] [iэ] [??] [u?], five of which are considered relatively pure: [a: ] [3: ], [i:], [u:] [ o: ].