Temporal and Aerodynamic Aspects of Velopharyngeal Coarticulation: Effects of Age, Gender and Vowel Height

Previous studies on the normal patterns of velopharyngeal coarticulation did not provide a multidimensional description of the phenomenon. The primary objective of this study was to determine the effects of age, gender and vowel height on the temporal and aerodynamic aspects of nasal airflow segments related to velar coarticulation in the normal speech of children and adults. A secondary objective was to determine the within speaker variability of the segments. Speakers consisted of 20 children between the ages of 5 and 7 years, 20 children between 9 and 11 years and 20 adult speakers 18 years or older. Nasal and oral air flows were collected from the participants using partitioned oro-nasal masks during the production of vowel-nasal-vowel sequences (VNV) including /ini/ and /ana/ embedded in two carrier phrases. Temporal and aerodynamic measurements were obtained for anticipatory and carryover nasal airflow for (VNV) sequences including absolute (in seconds) and proportional duration, as well as the volume of nasal airflow (in milliliters) and the ratio of nasal to oral-plus-nasal airflow volume. A mixed design 3 x 2 x 2 x 2 ANOVA procedure was used to determine the effects of age group, gender, vowel height and production level (type of carrier phrase) on temporal and aerodynamic aspects of anticipatory and carryover nasal airflow. In addition, coefficient of variation (CV) was computed for both temporal and aerodynamic measures as an index to speaker\u27s variability. Group Analysis of Variance 3 x 2 ANOVA procedures were used to determine the effect of age group, gender, or both on within speaker variability for all temporal and aerodynamic measurements. The results of the analysis suggest a significant age effect (p \u3c .001) on both temporal aspects and on the absolute volume (ml) of anticipatory nasal airflow. Duration, absolutely (sec) and proportionally, and volume of nasal airflow (ml) decreased with increasing age. No significant age effect was found for carryover nasal airflow. However, a significant interaction between gender and vowel height was found. Female speakers produced longer duration than male speakers on high vowel contexts, and women produced greater volume of nasal airflow (ml) and greater ratio of nasal to oral-plus-nasal airflow. A significant production level effect was also found. Generally, all speakers exhibited reduced absolute (sec) and proportional duration as well as reduced nasal airflow volume (ml) when the carrier phrase contained \u27say\u27 preceding the VNV sequence compared to the one without \u27say\u27. Results of the CVs analysis showed main effect of age as well as age and gender interaction. Results indicate a reduction on variability with increasing age. Older boys and men exhibited greater variability than older girls and women particularly on high vowel context. Results of the study indicate that children and adults produce distinct patterns of temporal and aerodynamic aspect of anticipatory nasal airflow. Findings were consistent with previous studies that reduction in duration of speech segment and reduction in variability is a general pattern of speech development. It is also suggested that subtle gender differences in oral-pharyngeal anatomy as well as vowel-specific production patterns may explain the gender difference on high vowels. Results of the study were discussed in the light of Gestural Phonology view of speech development and velar movement. Clinical implications were suggested for the diagnosis and treatment of patients with velopharyngeal dysfunction