Making a vocal tract closure longer and shorter

This study examined lip and tongue kinematics in stop and fricative consonants of different
durations. Native speakers of Japanese served as subjects. An analysis of the lower lip closing
movement indicated that it differed for the long and short labial consonants. In particular, the
lower lip reached its highest vertical position later during the closure for the long than for the
short consonants, and its deceleration was modified to keep it in contact with the upper lip for a
longer time. Thus, both the magnitude and timing of the lower lip movement were changed to
control closure duration. For the lingual consonants, the magnitude of the tongue movement
during the closure was larger for the long than for the short consonants. However, the speakers
reduced the average speed of the tongue during the closure for the long consonant This allowed
the tongue to maintain contact with the palate to produce the vocal tract closure.