Theory of phonetics

I. Classificatory description of English vowels.
II. The qualitative analysis of the English and Russian vowel systems.
III. Modifications of Vowels in Connected Speech.


I. Classificatory description of English vowels. 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. A minimum vowel system of a language is likely to take the form of a triangle:
I V
a
The most important characteristic of the quality of these sounds is that they are acoustically stable. They are known to be entirely different from one another both articulatorily and acoustically. 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:
I V
e o
a
English has developed a vocalic system of a much larger number of phonemes. The quality of a vowel is known to be determined by the size, volume, and the 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 characteristics, such as 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.
The analysis of the articulatory constituents of the quality of vowels
allowed the phoneticians to suggest the criteria which are conceived to be of great importance in classificatory description. They are:

1. 
   stability of articulation;
   
2. 
   tongue position;
   
3. 
   lip position;
   
4. 
   character of the vowel end;
   
5. 
   length;
   
6. 
   tenseness;