The purpose of this study was to investigate the influence of the anterior palatal form on speech. The subjects used were 36 male and 14 female dentitions, which were native Japanese speakers. The palate of each subject was impressed and the study cast was made. Each palatal form was examined and classified. Parameters involve the palatal form ; WD-index, IM-angle, A-angle, PL 1, PL2, and PL 3 were measured. The acoustic characteristics during /s/ production of subjects were analyzed with a digital acoustic analysis system. The first and second peak frequencies and consonant duration of /s/, the first, second and third formant frequencies of following vowels were measured. The relation between the palatal form and the acoustic characteristic of /s/ sound was discussed.
The following results were obtatined.
1. Palatal form was classified into three types: Type 1 represents a rounded square arch with a gentle anterior palatal slope and the maximumpalatal depth was low. Type 2 represents a rounded square arch with a sharp slope and the maximum depth was great. Type 3 represents a narrow paraboloid or V-shaped arch with a sharp slope and the maximum depth was great.
2. WD-index, IM-angle and PL 3 in male subjects were useful values to classify three palatal types, and WD-index, A-angle and PL 2 in female subjects.
3. The palatal form had little influence on the acoustic characteristics of /s/ sound.