BACKGROUND & PURPOSE: Electropalatography (EPG) records the location and timing of tongue’s contact against the hard palate during speech. It has been used to study abnormal tongue-palate contact patterns in individuals with articulation disorders associated with cleft palate. Currently it is difficult to define and quantify abnormal EPG patterns. Three contact indices have been used in studies on normal articulations – the dorsopalatal contact quotient (Qp) which reflects the degree of tongue dorsum raising; alveolar contact anteriority index (CAa) which indicates the place of articulation in the anterior two-third of the palate; and alveolar contact centrality index (CCa) which reflects the constriction width in fricatives. This study applies these indices to quantify different error patterns and differentiate error patterns from normal patterns. This approach might help to identify and quantify abnormal patterns automatically.
METHODS: Speakers were four children with articulation disorders associated with cleft palate and three children with normal articulations. Simultaneous EPG and acoustic data were recorded as they read aloud eight words with target consonants /t k s ʃ/ embedded in the word-initial position. The closure period of plosives /t k/ and the frication period of fricatives /s ʃ/ were annotated based on the waveform. The three indices were measured at five time points of the annotated segment – the onset, offset and three equally spaced time intervals.
RESULTS: Backing of /t/ to velar and correct /k/ production showed the highest Qp, followed by AVDA, patalalization, correct /t/ production, and glottal stop. The CAa for correct productions of /t s ʃ/ was higher than that of glottal productions. AVDA is characterized by a combination of high CAa and moderate Qp. Patterns where there was no central constriction and those where the constriction was deviated to one side showed very high CCa.
CONCLUSIONS: Results show that Qp and CAa, but CCa, are useful in indicating the place of articulation and differentiating different abnormal contact patterns.
MAIN OBJECTIVES OF PRESENTATION: We will present EPG data from children with articulation disorders associated with cleft palate and children with normal articulations to illustrate the usefulness of the contact index method on quantifying error patterns.