The differential influence of vowels and palatal covering on nasalance scores.

Objective :  To investigate whether nasalance scores would differ when the hard palate and soft palate were covered during speech. Design :  Nasalance scores were obtained during production of sentence stimuli loaded with differing vowel content across three conditions: (1) hard and soft palate uncovered (U); (2) hard palate covered by acrylic appliance (H); (3) both hard and soft palate covered by acrylic appliance (B). Sentences were loaded with high front, low front, high back, low back, or mixed vowels. Velopharyngeal closure was verified by nasoendoscopy. Participants :  Six female adults with normal speech and resonance provided the speech samples. Main Outcome Measures :  Nasalance scores for each of five sentences in each of three palatal conditions. Results :  Mixed and high front sentences had significantly higher mean nasalance scores in the U (P < .01) and H (P < .05) conditions but not in the B condition. For all sentence stimuli combined across palatal conditions, there was a significant difference in mean nasalance scores between H and B conditions (P < .05) but not between the U condition and either the H or B conditions (P > .05). Conclusions :  Data suggest that the primary place of transpalatal transfer of acoustic energy was the soft palate but only sentences with high-front vowels were affected by this phenomenon.