Covert contrast in velar fronting: An acoustic and ultrasound study.
There is growing evidence that speech sound acquisition is a gradual process, with instrumental measures frequently revealing covert contrast in errors perceived to involve phonemic substitution. Ultrasound imaging has the potential to expand our understanding of covert contrast by showing whether a child uses different tongue shapes while producing sounds that are perceived as neutralised. This study used an ultrasound measure (Dorsum Excursion Index) and acoustic measures (VOT and spectral moments of the burst) to investigate overt and covert contrast between velar and alveolar stops in child speech. Participants were two children who produced a perceptually overt velar-alveolar contrast and two children who neutralised the contrast via velar fronting. Both acoustic and ultrasound measures revealed significant differences between perceptually distinct velar and alveolar targets. One child with velar fronting demonstrated covert contrast in one acoustic and one ultrasound measure; the other showed no evidence of contrast. Clinical implications are discussed in this article.
a Department of Communicative Sciences and Disorders , New York University , New York , NY , USA.
Tara
T
McAllister Byun
a Department of Communicative Sciences and Disorders , New York University , New York , NY , USA.
Adam
A
Buchwald
b Department of Speech-Language-Hearing Sciences , City University of New York Graduate Center , New York , NY , USA.
Ai
A
Mizoguchi
D001184:Articulation Disorders / Q000000981:diagnostic imaging / Q000503:physiopathology; D002663:Child Language; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D013018:Sound Spectrography; D013061:Speech Acoustics; D013068:Speech Production Measurement; D014059:Tongue / Q000502:physiology; D014463:Ultrasonography
Acoustics; child speech; covert contrasts; ultrasound; velars