Zoe Roxburgh

Covert contrast and covert errors in persistent velar fronting

ABSTRACT Acoustic and articulatory studies demonstrate covert contrast in perceptually neutralised phonemic contrasts in both typical children and children with speech disorders. These covert contrasts are thought to be relatively common and symptomatic of phonetic speech disorders. However, clinicians in the speech therapy clinic have had no easy way of identifying this covertness. This study uses ultrasound tongue imaging to compare tongue contours for /t/and /k/in seven children with persistent velar fronting. We present a method of overlaying tongue contours to identify covert contrast at the articulatory level. Results show that all seven children, contrary to expectations, produced both /t/and /k/with near-identical tongue shapes showing no evidence of covert contrast. However, further analysis of one of the participants showed highly variable tongue shapes for /t/and /k/, including retroflex productions of both. Although not phonologically conditioned, this covert error is evidence of speech disorder at the phonetic level.

Multiple phonetically trained-listener comparisons of speech before and after articulatory intervention in two children with repaired submucous cleft palate.

ABSTRACT Cleft Palate (CP) assessments based on phonetic transcription are the “gold standard” therapy outcome measure, despite reliability difficulties. Here we propose a novel perceptual evaluation, applied to ultrasound-visual biofeedback (U-VBF) therapy and therapy using visual articulatory models (VAMs) for two children with repaired submucous CP. Three comparisons were made: post VAM, post U-VBF and overall pre- and post-therapy. Twenty-two phonetically-trained listeners were asked to determine whether pre- or post-therapy recordings sounded “closer to the English target”, using their own implicit phonological knowledge (prompted via orthographic representation). Results are compared with segment-oriented percent target consonant correct (PTCC) derived from phonetic transcriptions. Listener judgements and PTCC suggest that both children made improvements using both VAM and U-VBF. Statistical analysis showed listener agreement in each comparison, though agreement was weak. However, perceptual evaluation offers a straightforward method of evaluating the effectiveness of interventions and can be used by phonetically trained or lay listeners.