Articulation Characteristics of Children with Tongue Thrust Swallowing -First Report on An Acoustic Analysis of Alveolar /s/-

Abstract

Children with open bite with tongue thrust swallowing have anterior open bite or notable labial inclination of the incisor tooth in the maxilla and mandible. It was expected that children with open bite with tongue thrust swallowing would articulate the alveolar /s/ or /t/ as an interdental, however, there were a few studies using the Acoustic Analysis.
The purpose of this study was to cla rify the acoustical characteristic of the sounds /s/ in open bite patients. The formant frequency of the alveolar was extracted from the speech waveform in patients with open bite and compared to that of patients with normal bite.
We recorded the pronunciation of the short sentence ("ha na ga saita") that was articulated in patients with normal bite and patients with open bite from 3 years of age to 15 years of age. These sounds included the voiceless alveolar fricative /s/. The first and second formant for the voiceless alveolar fricative /s/ was analyzed. The frequencies of the first and second formant in patients with open bite were significantly higher than those in patients with normal bite. Putting the results of patients with normal bite and patients with open bite together, it was found as the alveolar became an interdental, the fricative became an approximant.
This result suggested that in patie nts with open bite the distance between the blade of the tongue and alveolar ridge is farther than in patients with normal bite, and the sound /s/ was not articulated as a fricative but as an approximants. The blade of the tongue came near the open end of vocal tract, and the sound /s/ became an interdental from the alveolar.