Using EPG data to display articulatory separation for phoneme contrasts.

A recurring difficulty for researchers using electropalatography (EPG) is the wide variation in spatial patterns that occurs between speakers. High inter-speaker variability, combined with small numbers of participants, makes it problematic (1) to identify differences in tongue-palate contact across groups of speakers and (2) to define 'normal' patterns during visual feedback therapy. This article shows how graphing EPG data in terms of articulatory separation of phoneme contrasts reduces these two problems to some extent. The graphs emphasise the importance of establishing the presence and extent of separation, as revealed in the EPG data, for phoneme contrasts produced by speakers. Separation graphs for contrasts /i/ - /u/, /s/ - /ʃ/ and /t/ - /k/ are presented using EPG data from adults and children with typical speech and those with speech disorders. When used in conjunction with acoustic and auditory perceptual analyses, it is proposed that representing articulation data in terms of separation will prove useful for a range of clinical and research purposes.