N. V. Tatsenko introduction to theoretical phonetics of english

Figure 5.6 - Centering diphthongs



И as in 'hear' and 'pier'. The starting point is a little closer than i in 'bit', 'bin'.
M as in 'care' and 'flair'. This diphthong begins with a vowel sound that is more open than the [e] of 'get', 'men'.
[иэ] as in 'pure' and 'tour'. For speakers who have this diphthong, this has a starting point similar to [o] in 'put', 'pull'. Many speakers pronounce [o:] instead.
The closing diphthongs have the characteristic that they all end with a glide towards a closer vowel. Because the second part of the diphthong is weak, they often do not reach a position that could be called close. The important thing is that a glide from a relatively more open towards a relatively closer vowel is produced.


Figure 5.7 - Closing diphthongs



Three of the diphthongs glide towards [i], as described below:
[ei] as in 'pray' and 'sleigh'. The starting point is the same as the [e] of 'get', 'men'.
[oi] as in 'joy' and 'boy'. The first part of this diphthong is slightly more open than [o:] in 'ought', 'born'.
^[ai] as in 'fry' and 'high'. This diphthong begins with an open vowel which is between front and back; it is quite similar to the [л] of the words 'cut', 'bun'.
Two diphthongs glide towards [o], so that as the tongue moves closer to the roof of the mouth there is at the same time a rounding movement of the lips. This movement is not a large one, again because the second part of the diphthong is weak.
[au] as in 'cow' and 'now'. This diphthong begins with a vowel similar to [ai]. Since this is an open vowel, a glide to [o] would necessitate a large movement, and the tongue often does not reach the [o] position. There is only slight lip-rounding.
[эи] as in 'go' and 'blow'. The vowel position for the beginning of this is the same as for the "schwa" vowel [э], as found in the first syllable of the word 'about'. The lips may be slightly rounded in anticipation of the glide towards [o], for which there is quite noticeable lip-rounding.
Beware that a diphthong is not just a combination of two vowels. For example, in the two-syllable word 'seeing', [i:] becomes [i] but it is not a diphthong because [i:] and [i] are not in the same syllable.
It has already been mentioned that one component of a diphthong is more prominent than the other. In the English diphthongs, it is usually the first element which is more prominent, but in other languages like French, this may be different. The two articulations of a diphthong are described as nucleus and a glide.
The most complex English sounds of the vowel type are the triphthongs. They can be rather difficult to pronounce, and very difficult to recognise. A triphthong is a glide from one vowel to another and then to a third, all produced rapidly and without interruption. For example, a careful pronunciation of the word 'hour' begins with a vowel quality similar to [a:], goes on to a glide towards the back close rounded area (for which we use the symbol [o]), then ends with a mid-central vowel (schwa, [э]). We use the symbol [аоэ] to represent the pronunciation of 'hour', but this is not always an accurate representation of the pronunciation.
The triphthongs can be looked on as being composed of the five closing diphthongs described in the last section, with [э] added on the end. Thus we get:
[ei] + [э] = [eia] [эи] + [э] = [эиэ]