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Vowels are more difficult to describe in articulatory terms because their articulation relies on variations of tongue position and of the shape of the mouth; no clear contact between organs of speech can be felt:

  • Vowels are voiced sounds
  • Vowels have syllabic function, i.e. every English syllable requires a vowel sound

The description of vowels in terms of articulatory features is not as straightforward as that of consonants which is why we need a different descriptive system for vowels. The reason is that in the production of vowels it is not possible to observe or perceive distinct places or manners of articulation distinguishing clearly between the different vowels. Furthermore, the feature of voicing cannot be employed in their description because all vowels are voiced. All of the vowels are formed in the oral cavity and as mentioned earlier no stricture in the speech tract hinders the flow of air. The position of the tongue, the shape of the lips and the jaw position determine the vowel and its quality, yet these features are much more difficult to observe and formulate into clear and distinct sets of features than in the system used in the description of the consonants. For this reason, Daniel Jones, professor of phonetics at University College London found a way of describing vowels based on articulatory features. He devised a so-called ‘Urmetrisches Bezugssystem’, i.e. a system which uses basic physiological parameters as a system of reference. He made x-rays of the mouth from the side of the face thus observing the position of the tongue and the shape of the oral cavity when speakers produced vowels sounds at different positions in the mouth. By taking as a point of reference the positions assumed by the articulators in the production of the most extreme vowel sounds at the front, centre and back of the mouth as well as those with the highest and lowest raising of the tongue, different width of mouth opening and lip rounding, he formulated the so-called vowel trapezoid, a chart in which all vowel sounds can be entered relative to the positions of those vowel sounds produced at the most extreme positions in the mouth. Jones thereby determined the so-called primary or cardinal vowel system which to this date is used as a system of reference in the description of vowel sounds in all languages of the world (cf. Cardinal vowel chart below).

Figure 1-2: Vowel trapezoid of the English vowel system

Figure 1-3: Vowel trapezoid of the Cardinal vowel system and the English vowel system

Figure 1-4: Examples of English vowels and their description