Vowels and diphthongs

When we examined consonants, we talked about the varying degrees of obstruction of the airflow in their production. As a general statement, we can say that the vocal tract is more open in vowels than in consonants. This, however, can be a tentative formulation, because as we saw in the discussion of glide/vowel separation, the consideration may be phonological and not phonetic.

For the characterization of vowels, we do not use the dimensions of place and manner of articulation, as there is no contact between the articulators. Instead, vowels are characterized by the position of the tongue and the lips. Since vowels are usually voiced, the voiced/voiceless distinction used for consonants is not relevant either.

If you examine the vowels of beat, bit, bait, bet, and bat in the order given, you will notice that your mouth opens gradually and the body of your tongue lowers gradually. A similar situation is observed if we go through the vowels of boot, book, boat, and bought; that is, gradual opening of the mouth and gradual lowering of the tongue. The difference between the two sets lies in the part of the tongue involved. While in the former set the front part of the tongue is involved (tongue pushed forward), the latter set focuses on the back of the tongue (tongue pulled back). The traditional type of chart used to plot vowel positions places the front vowels on the left, back vowels on the right, and central vowels in the middle. There are height dimensions: ‘high’ (or ‘close’), ‘mid’, and ‘low’ (or ‘open’), while the ‘mid’ is frequently divided into ‘high-mid’ and ‘low-mid’. Figure 2 shows the English vowels.

Another dimension of vowel description refers to the lip position. Four /ɔ, o, ʊ, u/ of the five back vowels, which are given in circles in the chart, are produced with rounded lips and thus are called ‘round’ (or ‘rounded’); all other vowels are unrounded.

Finally, in addition to the height, backness, and rounding characteristics, one other grouping, tense/lax, is given. This is a rather controversial issue. Here, suffice it to say that we will follow the distributional criteria and group /ɪ, ε, æ, ʊ, Λ/ as ‘lax’, while considering the rest ‘tense’.

The vowels we have described so far are considered to have a single, unchanging quality and are called ‘monophthongs’. (This is not uncontroversial for /i/ and /u/, and especially for /e/ and /o/) The vocalic elements of words such as bite, brown, and boy, on the other hand, involve a complex articulation whereby we move from one vowel to another. More specifically, we have /aɪ/, /aʊ/, and /ɔɪ/, respectively. Such sounds are known as ‘diphthongs’. The complete account of vowels and diphthongs, including their dialectal variations.