Automatic Assessment of Infants' Levels-of-Distress from the Cry Signals

It has long been an attractive prospect to monitor and assess infants' physical and emotional well-being by analyz- ing their cries. The feasibility of such an approach depends on the introduction of modern computer signal processing technology into infant cry research. In this paper, we first discuss the issue of quantifying the distress level of infants. We propose the use of a single item-the level of distress (L0D)-to describe parents' perceptual assess- ment of infants' distress situation from cry sounds. Then, we introduce the concept of cry modes and cry mode sequences to efficiently represent the time-frequency characteristics of infant cries. With the introduction of the cry mode representation scheme, a composite parameter-the H -value-is established as a descrip- tor of the LOD. The H-value can be derived from the cry sound signal. In our experiment, the H-value showed strong consistency with the parents' LOD rating. Finally, an automatic cry analysis system based on hidden Markov models (HMM's) is explained. This system automatically estimates the W-value from a cry sound signal. Testing with 58 different cries uttered by infants under various degrees of stimulation has shown that this HMM-based system is able to give assessments of the distress level of infants consistent with the perceptions of experienced parents. This work provides the basis for the design of automated devices for the monitoring and evaluation of cries of normal and sick infants.