Music & Language Studies

Murry, Thomas, Jeannette Hoit-Dalgaard, and Vincent L. Gracco. “Infant Vocalization: A Longitudinal Study of Acoustic and Temporal Parameters,” Folia Phoniatrica 35: 245-253 (1983).

The present investigation is a longitudinal study of cry and noncry vocalizations obtained from 1 infant at biweekly intervals from 2 to 12 weeks of life. (245)

The authors sought:

to determine if longitudinal trends existed in cry and nondistress vocalizations. (245)

Recordings were made about every two weeks for the first three months of life. A distinction was drawn between distress and non-distress vocalizations, principally on the basis of known context. The authors note that non-distress vocalizations first emerge during the eighth week of life. The cry samples were analyzed acoustically

to obtain F0, the duration of the vocalic segments, the amount of periodicity, aperiodicity and silence in the sample, and classification of melody contours. (246)

The researchers plotted a stylization of the intonation contours (termed melodygrams) abstracted from 0.1 s segment readings of periodic signals. Segments in excess of 0.4 s were classified from these stylizations as one of 7 melody types:

rising (R), falling (F), rising-falling (RF), falling-rising (FR), flat (FL), rising-falling-rising (RFR), or falling-rising-falling (FRF). (246)

They observe:

The falling contours are assumed to represent the natural physiologic state; that is, the fall in F0 results from a decrease in subglottic air pressure over the expiratory cycle. The rising or flat terminations, however, reflect phonatory modification of the airstream; that is, the natural falling contour is altered. This finding suggests that cry and nondistress vocalizations may be separated on the basis of final termination markers. (251)

As a result of these investigations, they conclude:

Examination of the similarities among the vocalization data revealed evidence of two developmental trends. A general increase in the main duration of vocalic segments was noted in all three phonatory conditions. Secondly, the cry data, especially the discomfort cry, showed a higher proportion of periodic phonation relative to silence as the infant matured. These trends appear to reflect increased respiratory and phonatory control which accompanies the normal developmental process. (251)