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.