Vowels are described differently than consonants in terms of their “places of articulation” as a result of no full or partial constrictions being made in the vocal tract. Vowels are articulated with an open and sonorous vocal tract, where different vowels are produced by different placements of the tongue body and lips as the active articulators (Zsiga, 2013).
Instead of using place of articulation to describe vowels, they are commonly described in terms of tongue height and lip rounding. A more detailed description of the domains of vowel articulation are provided in the following sections:
- Tongue Height: the tongue can move up or down in the mouth in order to produce different resonances in the oral cavity during vowel articulation. There are three possible tongue heights:
- High: the tongue body moves up towards the roof of the mouth (with no contact)
- Mid: the tongue body stays neutral, in the middle of the mouth
- Low: the tongue body lowers in the oral cavity for low vowels.
- Lip Rounding: there are two ways to distinguish vowels in terms of their roundedness. Lips may be either rounded or unrounded during vowel articulation.
- Rounded: round vowels are articulated with a “tense” rounded shape of the lips.
- Unrounded: unrounded vowels are articulated with a more “natural” state of the lips, where no tensing of the lips is made.
- Tongue Advancement: tongue advancement refers to whether or not the tongue is moved forwards or back in the mouth during vowel articulation. There are three possible positions for the tongue in terms of advancement.
- Front: vowels that are produced with a fronted tongue position.
- Central: the tongue remains neutral in the centre of the mouth.
- Back: the tongue moves further back in the mouth during articulation.
- Diphthong: diphthongs are vowels that are articulated in a “two-part” sequence. Diphthongs can be thought of as two vowels being articulated within a single syllable, the first vowel being a normal vowel and the second being glide-like.
- Tense versus Lax: the distinction between “tense” or “lax” vowels refers to the “effort” of the tongue muscles during articulation. Tense vowels tend to have a more constricted tongue, creating a longer, higher, and louder sound than lax vowels. Lax vowels are produced with a more “relaxed” tongue position and are often quieter
- Schwa: a schwa is a vowel that is articulated with a completely neutral tongue and lip position. The lips are unrounded and the tongue is at a central position in the mouth.