The first who tried to describe and classify vowels irrespective of the mother tongue was Daniel Johnes. He worked out a system of 8 cardinal vowels. This system is an international standard which presents a set of artificial vowels and which contains all the vowel types existing in different languages of the world. In reference to this system the vowel sounds of any real language of the world may be described and classified and sometimes this system is called the vocalic Esperanto.
close i u
half-close e o
half-open ə ɔ
open a ɑ
The tongue can move horizontally and vertically and according to these movements Daniel Johnes represented his 8 cardinal vowels. The system of cardinal vowels has a great theoretical value and it is used as a basis for classification of vowels in different languages.
Russian phoneticians suggest classifying vowels according to the following principle: 1) position of the lips; 2) position of the tongue; 3) degree of tenseness; 4) length; 5) stability of articulation.
1) position of the lips. According to this principle vowels are classified into rounded [ɔ, ɔ:, u, u:]and unrounded.
2) Position of the tongue. The bulk of the tongue conditions the production of different vowels most of all its horizontal and vertical movement forms vowels of a particular language.
According to the horizontal movement English vowels are classified into the following groups: 1) front vowels [i:, e, æ], nucleus of the diphthongs[eɪ, ɑɪ, ɛə]; 2) front retracted [ɪ], nucleus of the diphthong [ɪə]; 3) mixed vowels [ə, ə:], the term mixed is used by the Russian phoneticians because in the production of this group of vowels the tongue is raised towards the junctions between the soft and hard palates. British phoneticians call these vowels central, because the central part of the tongue is raised highest in their pronunciation; 4) back advanced [u,ɔ, ʌ], the nucleus of the diphthongs [əʊ, ʊə]; 5) back vowels , [u:,ɔ:,ɑ], diphthongs [ɔɪ, ɛə].
According to the vertical movement of the tongue English vowels have been traditionally subdivided into 3 groups: 1) high (close) vowels [ɪ,i:,u,u:]; 2) mid-vowels [e,ə,ə:,a], nucleus of [əu,ɛə]; 3) low (open) vowels [ʌ, ɔ, ɔ:, ɑ:], nucleus [aɪ, au].
3) The degree of muscular tension. Classified into tense and lax.All long vowels are tense, short vowels are lax.
4) Length of vowels. English vowels are historically subdivided into long and short. Vowels length depends on a number of linguistic factors. Firstly, position of the vowel in a word [si: - si:d – si:t] - [si: - si· – si]. For the voiceless consonants the length of a long vowel is the shortest.
Word accent. In the stressed syllable the vowel has the maximum length. 'forecast [ɔ:], fore'cast [ ɔ·,ɑ:]. The number of syllables in a word, e.g. verse, university. In a mono-syllabic word the vowel is longer, than in a poly-syllabic one. The character of the syllabic structure. In the words with open types of syllable vowels are longer than in words with closed types.