| Abstract: | Acoustic properties of the cries of 14 infants were evaluated at both 2 and 4 weeks of age when the infants were lying in a supine position and when they were sitting upright in a car seat. In the upright position, infants' breathing was more rapid and showed less individual variability. The fundamental frequency of their cries increased in the upright position, but this increase was likely attributable to increased arousal or distress, not to posture per se. There were no differences in acoustic measures related to vocal tract shape in the supine versus upright positions. Across age, there was a decline in fundamental frequency. Individual difference stability of most acoustic measures was moderate to high. The importance of postural effects on the acoustic features of cries was discussed. |
