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This paper surveys acoustic studies of speech development and discusses the data with respect to the anatomical and neuromuscular maturation of the speech mechanism. The acoustic data on various aspects of speech production indicate that the accuracy of motor control improves with age until adult-like performance is achieved at about 11 or 12 years, somewhat after the age at which speech sound acquisition usually is judged to be complete. Other topics of discussion are (1) problems in the spectrographic analysis of children's speech, (2) formant scale factors that relate children's and adults' data, and (3) identification and diagnosis of developmental disorders through acoustic analyses of speech sounds.
Raymond D. Kent (Wed,) studied this question.