Developmental aspects of infant's cry melody and formants.

This paper deals with the analysis of cry melodies (time variations of the fundamental frequency) as well as vocal tract resonance frequencies (formants) from infant cry signals. The increase of complexity of cry melodies is a good indicator for neuro-muscular maturation as well as for the evaluation of pre-speech development. The variation of formant frequencies allows an estimation of articulatory activity during pre-speech vocalization. Subjects are three pairs of healthy identical twins (monocygozity determined by DNA-fingerprint). Spontaneous cries of these six children were recorded at different ages: 8th-9th week, 15th-17th week and 23rd-24th week. Analysis of 136 cry melodies and intensity contours was made using KAY-CSL 4300/MDVP. For formant estimation a spectral parametric technique was applied, which was based on autoregressive models (Digital spectral analysis with applications, 1987) whose order is adaptively estimated on subsequent signal frames by means of a new method (Med. Eng. Phys. 20 (1998) 432; Utras. Med. Biol. 21 (1995) 793). Cry melodies exhibited an increasing complexity during the observation period. Beginning with the second observation period (15th-17th week) an increasing coupling and tuning between melody and resonance frequencies was observed, which was interpreted as "intentional" articulatory activity. Possible applications are in cry diagnosis as well as in the evaluation of pre-speech development.