ABSTRACT
The present chapter aims to consolidate existing knowledge on vowel realization in hearing impairment (HIMP) by tracing important themes in the relevant literature and assembling, as far as possible, the core findings that suggest some general trends in vowel production for affected speakers. We also offer a brief case study of vowel patterns among hearing-impaired (HI) speakers of one variety of Northern-Irish English, comparing a sample of their tokens with those of broadly-matched control subjects. Based on available work, and the data presented here, we attempt to capture aspects of between-group variation that exist for the HI and normal-hearing (NH) populations at the level of formant frequencies, as well as some consistent group articulatory adjustments that tend to map vowel spaces in systematic ways. A further intention of this chapter is to disentangle the factors that have been responsible for creating a less than coherent picture of how HIMP is likely to affect speech production more generally, as well as with specific reference to its likely effects upon vowels. For all groups of HI speakers, nonetheless, it is widely acknowledged in the literature that vowels play a key role in allowing speech to be perceived clearly by a wide range of listeners and that their disruption is, at least to some extent, problematic.
