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The effect of vowels on nasalance scores
K E Lewis1, T Watterson, T Quint
1University School of Nevada School of Medicine, Department of Speech Pathology & Audiology, Reno 89557, USA. klewis@med.unr.edu
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/, /ae/, 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 /ae/ 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.