[Studies on influences of artificial palatal plates on pronunciation]

The purpose of this study was to investigate the influence of the alteration of palatal form on pronunciation. Three types of artificial palatal plates simulating the upper complete denture, which artificial posterior teeth position was more lingually than natural dentition, were made for each dentulous subject. Difficulty of articulatory movements and sound qualities were assessed when the subjects pronounced /sa/, /si/, /ka/, /ki/, /ci/, /hi/, and /ri/ with each plate. The distortional sounds judged by auditory psychological experiment were analysed by acoustic methods, and mandibular movements during pronunciation of them were measured.

1. /ki/ and /hi/ were affected remarkably when the posterior position was more lingually, and /ri/, /ci/ and /sa/ were also affected. 2. The acoustic characteristics of distortional sounds were estimated by peak trajectories, supectrum envelopes, peak frequencies and sound waveforms of consonant parts, formant frequencies and formant trajectories of following vowels, and segemental durations. 3. Mandibular movements did not influence directory on the acoustic characteristics of distortional sounds. It was thought that tongue and lips mainly influenced on those.