N. V. Tatsenko introduction to theoretical phonetics of english

[ai] + [э] = ^э] [au] + [э] = [аиэ]
М + ^[э] = ^[эт^]
The principal cause of difficulty for the foreign learner is that in present-day English the extent of the vowel movement is very small, except in very careful pronunciation. Because of this, the middle of the three vowel qualities of the triphthong (i.e. the [i] or [o] part) can hardly be heard and the resulting
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sound is difficult to distinguish from some of the diphthongs and long vowels. To add to the difficulty, there is also the problem of whether a triphthong is felt to contain one or two syllables. Words such as 'fire' [faia] or 'hour' [aoa] are probably felt by most English speakers (with BBC pronunciation) to consist of only one syllable, whereas 'player' [pleia] or 'slower' [slaoa] are more likely to be heard as two syllables.
This is partly because there is so much variation in the amount of vowel movement according to how slow and careful the pronunciation is, and also because the "careful" pronunciation can be found by looking at the description of the corresponding diphthong and adding [a] to the end. However, to help identify these triphthongs, some example words are given here:
[eia] 'layer', 'player' [эиэ] 'lower', 'mower'
[aia] 'liar', 'fire' [аиэ] 'power', 'hour'
[aia] 'loyal', 'royal'
It seems that triphthongs in BBC pronunciation are in a rather unstable state, resulting in the loss of some distinctions: in the case of some speakers, for example, it is not easy to hear a difference between 'tyre' [taia], 'tower' [taoa], 'tar' [ta:]. BBC newsreaders often pronounce 'Ireland' as [a:land]. This shows a change in progress in the phonemic system of RP [Roach 2009, p. 20].

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   Another principle we should consider from phonological point of view is the position of the tongue. For the sake of convenience, the position of the tongue in the mouth cavity is characterised from two aspects, that is the horizontal and vertical movement.
   

According to the horizontal movement (depending on the part of the tongue that is raised) most vowels are classified into front, back, and central:

1. 
   when the front part of the tongue is raised towards the hard palate, the vowel is called front: [i:], [i], [i(s)], [e], [ei], [ж], [е(э)], e. g. in meet, get, or land.
   
2. 
   when the back part of the tongue is raised towards the soft palate, the vowel is called back: [а:], [э:], [u:], [о], [о (э)], as in star, dog, law, or soon.
   
3. 
   when the front part of the tongue is raised towards the back part of the hard palate, the vowel is called central: [л], [о], [з:], [э], [з(о)], [е(э)], e.g. in about, much, or nurse.
   

As to the tongue position in its vertical movement (depending on the height of the tongue) British scholars distinguish high, low, and mid vowels:

1. 
   when the front or the back of the tongue is raised towards the roof of the mouth, the vowel is called high: [i:] [u:], [i], [o], ^(э)], [о (э)], e. g., in pill, meet, look, or soon.
   
2. 
   when the front or the back of the tongue is as low as possible, the vowel is called low: [e^)], [э:], [a(i)], [ж], [a (i, u)], [a:], as, e. g., in land, star, or dog.
   
3. 
   when the tongue occupies the position intermediate between the high and the low one, the vowel is called mid: [e], [з:], [э], [e(i)], [з(о)], [л], [о], e.g. in get, or the unstressed [э] in about.
   

These high-low and front-back dimensions of vowel articulation are also referred to as vowel quality. To illustrate how the articulatory properties of vowels relate to each other, a vowel chart is commonly used as a reference system. The chart below describes the basic vowel qualities of most standard varieties of English together with their phonetic transcription.

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