The Effect of Vowels on Nasalance Scores

Abstract

Objective: Nasalance scores were compared for nine different speech stimuli with vowel content controlled. Design: The nine speech stimuli included four vowels spoken in isolation and five sentences. The four vowels were /i/, /u/, /æ/, and /a/. Four of the five sentences were loaded with High Front, High Back, Low Front, or Low Back vowels, and the fifth sentence contained a mixture of vowel types. Setting: Academic and clinical craniofacial center. Subjects: The subjects were 19 children with velopharyngeal dysfunction (VPD) and 19 children without history of communication disorder. Main Outcome Measures: The main outcome measures were the nasalance scores associated with the nine different speech stimuli for two groups of subjects. Results: For the VPD group, analysis of variance procedures revealed that nasalance scores for high-vowel sentences and the mixed-vowel sentence were significantly higher than the nasalance scores for the two low-vowel sentences. This pattern was the same for the non-VPD group except for the High Back/Low Back contrast, which was not significant. In both groups, nasalance scores for sustained vowels were significantly higher for the High Front vowel /i/ than for any other vowel, and nasalance was significantly higher for the High Back vowel /u/ than for either of the Low vowels /æ/ or /a/. There was no significant difference between Low vowels. Conclusion: Nasalance scores may be affected by the vowel content of the speech stimulus. This should be taken into consideration on a clinical basis and for research purposes.