Vowel reduction as information loss

Vowel reduction suppresses phonetic information in the speech signal and should be understood as having an analogous impact on phonological representations. Reduction follows two apparently contradictory routes in vowel space, yielding either centralised values (the ‘centripetal’ pattern) or the corner values a, i, u (the ‘centrifugal’ pattern). What unifies these vowels is the relative simplicity of their acoustic spectra compared to those of mid peripheral vowels. Spectral complexity can be taken as one measure of the amount of phonetic information present in a speech signal at a given time. On this basis, centripetal and centrifugal reduction can both be construed as resulting in a loss of phonetic information. In selectively targeting non-prominent positions, reduction has the effect of enhancing syntagmatic contrasts among vowels. Representing vowels in terms of three basic components manifested as a, i and u allows informational asymmetries of this sort are to be directly recorded in phonological grammars.