The 1st problem of phonological analysis is to establish the phonemes in a definite language. This can be done with the help of particular phonological rules. There exist 2 principal methods of phonological analysis: distributional and semantic.
1) The distributional methodis based on the phonological rule that different phonemes can freely occur in one and the same position, while allophones of one and the same phoneme occur in different positions. E.g. /pi:/ - /bi:/, p and b are in the same position. That's why the distributional method of analysis is a purely formal method of identifying the phonemes of a language. This method works even if a linguist doesn't know the language he analysis.
2) The semantic method is based on the phonological rule that a phoneme can distinguish words when opposed to one another or to a zero phoneme in an identical phonetic position. The oppositions when a phoneme is opposed to a phoneme is called a phonological opposition, e.g. sees – seat. When a phoneme is opposed to a zero phoneme is called zero opposition, e.g. sea – seas. The pairs of words which differ only in one speech sound are called minimal pairs. The semantic method attaches great significant to meaning. The investigator studies the function of sounds by collecting minimal pairs of words in the language. If 2 speech sounds distinguish words with different meanings they form a phonological opposition and are realizations of 2 different phonemes. If not they are allophones of one and the same phoneme. The method was used to study the phonetic structure of the small nations of the former Soviet Union and it helped to create written forms of these languages.
There are some cases when the establishment of phonological oppositions is not enough to determine the phonetic status of the sound. In the English language there are some sounds of a complex nature. They are /tʃ,dʒ,tr,dr,ts,dz/. In the English language these sounds form phonological oppositions and distinguish words. Head - hedge, tie - try, die - dry, buds - buzz, eat - each, head - hats. Are all those combination mono-phonemic or bi-phonemic? There are rules worked out by Nikolay Trubetskoy which help to answer this question: 1) a phoneme is indivisible, that's why no syllabic division can occur within a phoneme; 2) a phoneme is produced by one articulatory effort; 3) the duration of a phoneme should not exceed the duration of other phonemes in the language. The combination of /tʃ,dʒ/ in such words as cheese, jail are monophonemic, because acoustic physiological analysis proved that these sounds are produced by one articulatory effort and no syllabic divisions occur within these phonemes. The clusters /ts,dz/ are bi-phonemic combinations because their duration exceeds the average duration of the sounds /t,d,s,z/. /tr,dr/: the phonetic status of these clusters is not decided yet. Daniel Johnes calls them affricats, as well as /tʃ,dʒ/, but most phoneticians regard them as bi-phonemic clusters. The same problem concerns the phonemic status of the English diphthongs and so-called triphthongs, whether they are mono-phonemic or bi-phonemic. The syllabic and articulatory indivisibility of English diphthongs determines their mono-phonemic character in English. Triphthongs /aiə,auə/: It has been proved that they can not be considered as mono-phonemic, because they are not produced by single articulatory effort and there is an increase in the force of articulation of intensity not only for the first element, but for the 2nd as well. Moreover the syllabic division generally occurs between the diphthong and the third element, e.g. 'flower'. So that's why they are combinations of a diphthong and a neutral vowel.
In this way it was established that in Standard English pronunciation which is called received pronunciation there are 12 vowels monophthongs, 8 diphthongs and 24 consonant phonemes.