Chapter Summary
Vowels are produced when
vocal fold vibration excites the resonances of the vocal tract. The
excitation spectrum is filtered by the vocal tract, giving rise to peaks in
the output spectrum which are known as formants. The patterning of three
lowest frequency formants essentially determines vowel quality. This
patterning can be related to the articulatory features of vowels (height,
location, lip position). Vowels may be long or short, and may be
monophthongs or diphthongs. The auditory properties of vowels can be related
to a diagram known as the vowel quadrilateral, and fixed landmark qualities
in the quadrilateral are known as cardinal vowels. Symbols for these,
together with additional symbols and diacritics permit the transcription of
vowel qualities.
Languages make use of the basic vowel features
in a wide variety of ways. Vowel systems range from the very small with
only three vowels to the quite large with 10 or more vowels. Some languages
increase the size of their vowel inventory by the use of modifications such
as nasalisation, length distinctions and the addition of diphthongs.
Vowels change over time more rapidly than
consonants do and vowels can differ quite significantly from one accent of a
language to another. Two accents may have different vowel systems.
They may differ in the lexical incidence of vowels and the precise phonetic
qualities of equivalent vowels may differ.