本研究旨在整合知覺評估與語音聲學分析，去檢驗腦性麻痺者元音構音特徵與說話清晰度的表現，進而探究元音構音空間的限制與說話清晰度缺損之間的關聯性。受試者為二十名腦性麻痺的男性青年，且其構音運動普遍受到神經肌肉控制不佳的影響，呈現嚴重度不一的說話障礙。說話清晰度語料來自受試者十八個含有端點三元音/i/、/a/、和/u/的中文雙字詞（例如：地道、大道、答對）。每一名腦性麻痺者說話清晰度的指標，則為三位評分者以語音項目辨識(item identification)方式所正確聽辨語音的平均百分比。在語音聲學分析的作業中，針對腦性麻痺者產生元音所運用的構音空間大小加以測量，並以十名年齡相當的男性大學生為對照組。研究結果顯示，相對於說話正常的對照組，腦性麻痺說話者的元音構音空間明顯縮小。進一步探究個別說話者元音構音空間的大小與其說話清晰度之間的相關程度，則發現二者之間有顯著正相關存在(r=3612, p<.01)；也就是說當腦性麻痺者所使用的元音構音空間愈受限制，則其說話清晰度愈差。元音構音空間的緊縮可視為降低腦性麻痺者說話清晰度的重要因素，因而在口語溝通復健時可將此構音特徵視為目標，列入評估說話清晰度或設計治療方案的考量。

The purpose of this study was to examine the association between the vowel working space and speech intelligibility using both acoustic analysis and perceptual approaches. Twenty mandarin-speaking young adults with cerebral palsy served as the subjects. In speech recordings, subjects read 18 bisyllabic words containing the corner vowels /i/, /a/, and /u/ using their habitual speaking rate and intensity. Each speaker's word was transcripted by three normal listeners during the item identification task and the average percentage of correct vowel identifications were used to indicate the speech intelligibility for individual cerebral-palsied speakers. For the acoustic analysis, the vowel space area on first(F1) and second(F2) formant plane of the corner vowels were determined from words produced by 20 speakers with cerebral palsy and 10 age-matched normal speakers. Results revealed that vowel space area of the speakers with cerebral palsy was significantly smaller than those of their controls. Positive correlation was obtained between vowel area and the speech intelligibility(r=.612, p<.01). Results suggest that the restricted vowel working space may adversely affect speech intelligibility for speakers with cerebral palsy. The vowel working space area could be an effective meaure of assessing speech intelligibility and also one of the speech treatment targets for cerebal-palsied speakers.