Velocity Differences Between Velum Raising and Lowering Movements.

This study investigated the intrinsic velocities of raising and lowering movements of the velum that are related to its biomechanical structure and aerodynamic conditions. To this end, five subjects produced cyclic transitions between nasals and fricatives as in /s-n-s-n-s-.../ with flat intonation and at two specific speaking rates to minimize contextual and prosodic effects. The velar movements were inferred from the movements of the lateral pharyngeal wall in ultrasound image sequences, which are strongly correlated. The results indicate that velum raising was significantly faster than velum lowering for the two male subjects (24%–49% faster, depending on the subject and speaking rate), but not for the three female subjects. Possible biomechanical and aerodynamic reasons for the observed velocity differences are discussed. The results can inform the interpretation of kinematic data of velar movements with regard to underlying neural control, and improve movement models for articulatory speech synthesis.