In order to understand the speech developmental process in infants from birth onwards, and design an instrument suitable to relate early infant sound productions to basic elements of adult speech, we tried to map the sensorimotoric development of the sound producing mechanism and possibly trace any systematics within the process. Subsequently we intend to describe the acoustic aspects of the sound productions within well defined motoric stages.

A method to study this developmental process was designed, based on the source-filter model of speech production. Within the framework of the anatomical and physiological capacities of the infant, source activities were described in aspects of phonatory development. Filter activities were represented by developmental aspects of articulatory movements. A breath group was used as a segmentation unit.

This method resulted in six clearly recognizable, sensorimotoric developmental stages in the infant's sound productions in the first year of life. Based on these results we tried to mark within the sound productions of one infant in his first year of life, each of the stages I-V by a number of acoustic features.