Comparing deaf and hearing Dutch infants: changes in the vowel space in the first 2 years.

The influence of the mother tongue on vowel productions in infancy is different for deaf and hearing babies. Audio material of five hearing and five deaf infants acquiring Dutch was collected monthly from month 5-18, and at 24 months. Fifty unlabelled utterances were digitized for each recording. This study focused on developmental paths in vowel productions. The applied automated band filtering analysis is F0-independent and results in a spectral envelope, sampled in a 40-dimensional space. Via a Principal Component Analysis (PCA, data reduction), a vowel space for normally hearing 2-year-olds was constructed, enabling the projection of the individual developmental data of the infants in a two-dimensional reference plane. Comparison of the results for the hearing and the deaf infants over 2 years indicates individual as well as group differences. The amount of hearing loss as well as the communication styles seem to be important factors in explaining differences between the infant categories.