Effects of velar resistance on speech aerodynamics

The level of intelligibility attained by speakers with cleft palate reflects not only the ability to achieve adequate velopharyngeal closure but other complex variables as well. When closure is inadequate, performance is influenced by compensatory responses of the tongue, vocal folds, respiratory muscles and nasal valve. The purpose of the present study was to determine how a loss of velar resistance associated with velopharyngeal inadequacy affects speech pressures and airflow. The pressure-flow technique (Warren, 1979) was used to assess mean airflow rate, mean intraoral and nasal pressures and velopharyngeal orifice areas in 211 subjects diagnosed as having cleft palate or velopharyngeal inadequacy. The data revealed that resistance fell as velopharyngeal orifice area increased. Intraoral pressures also fell as resistance dropped while nasal pressures and airflow rate increased. These findings suggest that individuals with velar inadequacy and associated low velar resistance compensate by increasing airflow rate in an attempt to maintain adequate pressures for consonant sound production.