title: Acquisition of vowel articulation in childhood investigated by acoustic-to-articulatory inversion.
abstract: While the acoustical features of speech sounds in children have been extensively studied, limited information is available as to their articulation during speech production. Instead of directly measuring articulatory movements, this study used an acoustic-to-articulatory inversion model with scalable vocal tract size to estimate developmental changes in articulatory state during vowel production. Using a pseudo-inverse Jacobian matrix of a model mapping seven articulatory parameters to acoustic ones, the formant frequencies of each vowel produced by three Japanese children over time at ages between 6 and 60 months were transformed into articulatory parameters. We conducted the discriminant analysis to reveal differences in articulatory states for production of each vowel. The analysis suggested that development of vowel production went through gradual functionalization of articulatory parameters. At 6-9 months, the coordination of position of tongue body and lip aperture forms three vowels: front, back, and central. At 10-17 months, recruitments of jaw and tongue apex enable differentiation of these three vowels into five. At 18 months and older, recruitment of tongue shape produces more distinct vowels specific to Japanese. These results suggest that the jaw and tongue apex contributed to speech production by young children regardless of kinds of vowel. Moreover, initial articulatory states for each vowel could be distinguished by the manner of coordination between lip and tongue, and these initial states are differentiated and refined into articulations adjusted to the native language over the course of development.
authors.affiliation: Graduate School of Education, The University of Tokyo, Bunkyo-ku 7-3-1, 113-0033 Tokyo, Japan. Electronic address: hiro084@gmail.com.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Oohashi
authors.affiliation: Graduate School of Education, The University of Tokyo, Bunkyo-ku 7-3-1, 113-0033 Tokyo, Japan.
authors.forename: Hama
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Graduate School of Education, The University of Tokyo, Bunkyo-ku 7-3-1, 113-0033 Tokyo, Japan.
authors.forename: Gentaro
authors.initials: G
authors.lastname: Taga
mesh_terms: D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007802:Language; D007804:Language Development; D008297:Male; D010700:Phonetics; D013060:Speech / Q000502:physiology; D013061:Speech Acoustics; D013062:Speech Articulation Tests / Q000379:methods* / Q000639:trends; D013067:Speech Perception / Q000502:physiology; D014059:Tongue / Q000502:physiology
keywords: Acoustic-to-articulatory inversion; Articulation; Development; Speech