기능적 음성장애 유무와 발화 과제에 따른 구강 개방 비교 연구

Abstract

The speaker with functional voice disorder has a characteristic of overly tensed muscle around vocal folds by constant overuse of voice when they speak. Not open mouth habits with overly tensed muscle around larynx and vocal tract causes excessive contact between vocal folds. Furthermore, it induces reduction of resonance in mouth, and might sustain the problem of vocal folds by generating hyperadduction excessive vocal adduction in order to compensate insufficient resonance. Therefore it is necessary to make mouth more open for the reduction of tension near larynx and the improvement of excessive vocal adduction. The area of vowel triangle or quadrilateral means the extent of mouth opening, and it can be measured by the vowel space area. Studies about vowel space area have largely focused on the field of speech sound disorder. However, the study of mouth opening targeting functional voice disorder speaker is a lot of insufficient compared to the necessity, thus the study should be carried out in order to find out the characteristics of their mouth opening. The present study performed to investigate the characteristics of mouth opening of voice disorder speakers by comparing the two groups, normal group with normal vocal folds and functional voice disorder group with the diagnosis of functional voice disorder(depending on whether having functional voice disorder or not) and the area of vowel space according to word and sentence(utterance tasks). The subjects of 20 normal grown-up women and 20 grown-up women with functional voice disorder have participated in the experiment. The experimental task was consisted of 24 two-syllable words of phonetically balanced words and 24 sentences(‘write down _’), and it let the subjects to read them with ordinary pitch, loudness and speaking rate in order to collect voice data representing mouth opening in ordinary life. Formant frequency(F1, F2) of /a/, /i/, /u/ was analyzed using Linear Predictive Coding(LPC), in the main programs of CSL. Through the measured F1 and F2, Euclidean distance calculated between vowels such as /a-i/, /i-u/ and /a-u/, and the vowel space area. Results of the study are as followings. First, Euclidean distance of /a-i/, /i-u/ and /a-u/ by speaking task within the both groups was significantly short in sentence. In addition, the vowel space area according to speaking task was smaller when produced sentence rather than word. Second, the Euclidean distance depending on voice disorder or not has shown that the distance of the vowel /a-i/ of the voice disorder group was shorter than the normal group, and there was no difference in the distance of the vowel /i-u/ and /a-u/ between the two groups. In the case of production of sentences, all Euclidean distance of the voice disorder group were shorter than that of normal group. Moreover, the vowel space area according to voice disorder turned out to be smaller among voice disorder group in both words and sentences and there was larger standard deviation in voice disorder group. There was no interaction effect between groups and speaking tasks. The study, we were able to find that mouth opening is decreased since the accuracy of articulation drops due to co-articulatory influence, speaking rate and duration time of vowel when the length of speaking task is long. In addition, the speaker’s habit of excessive vocal adduction and tension affects the reduction of Euclidean distance and mouth opening by generating excessive tension of larynx and its peripheral muscles. There was not a significant difference in the /i-u/ and /a-u/ among the groups in terms of the Euclidean distance, which implies that the voice disorder group tend to open their mouth more when they speak words to produce better voice. It supports the fact that the voice disorder group cannot utilize mouth resonance properly by the result that the voice disorder group’s vowel space area is smaller than the normal group in the speaking tasks. This study showed that speaker’s vocal folds contact problem is related to mouth opening. And we obtained an evidence to improve voice problem, and to increase mouth resonance by better mouth opening. And the study proved the necessity of treatment focused on mouth opening among voice disorder speakers in clinical setting. It is necesssary that compare mouth opening between male and female and extent of mouth opening when they speak long sentence or talk about story. And it would be more meaningful to improve excessive tension of muscle of the voice disorder speaker if study compares mouth opening according to the severity of voice disorder.