Longitudinal study of the fundamental frequency of hunger cries along the first 6 months of healthy babies.

Potentially rich in information, the baby's cry has motivated several researches along the years. Although most of these studies have generated important knowledge about the baby's cry, they were focused on the neonatal period. The few longitudinal studies on changes in the acoustical features of the cry over the baby's growth have been done with a small sample and a large recording interval. Aiming to overcome such methodological limitations, this work investigated hunger cries using a more representative sample size (30 babies) and time resolution (biweekly intervals) from birth to 6 months of baby's age. The findings indicate that the fundamental frequency (f0) of the cry signals did vary more than previously reported in the literature. The results showed a widespread oscillatory behavior in f0 evolution along all the 6 months with an especially significant decrease from birth to the 15th day of life. The present results are not clinically applicable yet, but they pointed some novel aspects of the f0 mean values along the baby's growth. These findings and further longitudinal studies can help standardize age-related cry parameters, which are essential for medical and language development researches.