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Unlike consonants, vowel sounds are created without an appreciable obstruction of the airflow. Instead of blocking the air, the speaker phonates while positioning the tongue and configuring the lips in a variety of non‐obstructive ways. These articulatory gestures change the RESONANCE properties of the vocal tract. Since all English vowels are voiced, vowel articulation modifies the acoustic shape of the laryngeal buzz. If you sustain voicing continuously while moving your tongue into different vowel configurations, you will get a sense of how resonance changes. It's worth noting here that English vowels fall into two broad categories: 1) monophthongs, in which one basic tongue position is the target, like the /i/ of see, and 2) diphthongs, which entail tongue movement from one distinct tongue position to another, like the /aʊ/ of cow.

We can't capture the differences among vowels in terms of manner of articulation because they are all produced in essentially the same manner: they are all relatively “open” sounds. Also, as already mentioned, they are all voiced in English. However, vowels do differ in place of articulation in the sense that their approximate tongue locations vary both vertically and horizontally. They also differ in a dimension known as tenseness and in the way the lips are shaped. Our list of descriptors for English vowels is summarized in Table 4.3.

Table 4.3 Descriptors for English Vowels

Dimension	Meaning	Possible Values
Height	Vertical location of the highest point of the tongue	High, mid, or low
Advancement	Horizontal location of the highest point of the tongue	Front, central, or back
Tension	Whether or not the vowel is said to entail muscular tension	Tense or lax
Lip configuration	Degree to which the lips are spread as opposed to shaped like an “o”	Unrounded or rounded

Figure 4.2 Tongue positions for front (left) and back (right) vowels (derived from x-ray images)

(Source: Adapted from https://commons.wikimedia.org/wiki/File:Cardinal_vowel_tongue_position‐front.png and https://commons.wikimedia.org/wiki/File:Cardinal_vowel_tongue_position‐back.png)