The development of voiceless sibilant fricatives in Putonghua-speaking children

Purpose: The aims of the present study are (a) to quantify the developmental sequence of fricative mastery in Putonghua-speaking children and discuss the observed pattern in relation to existing theoretical positions, and (b) to describe the acquisition of the fine-articulatory/ acoustic details of fricatives in the multidimensional acoustic space. Method: Twenty adults and 97 children participated in a speech-production experiment, repeating a list of fricative-initial words. Two independent measures were applied to quantify the relative sequence of fricative acquisition: auditory-based phonetic transcription and acoustics-based statistical modeling. Two acoustic parameters—fricative centroid frequency and F2 onset—were used to index tongue-body and tongue-tip development, respectively. Results: Both transcription and statistical modeling of acoustics yielded the sequence of /ɕ/ → /ʂ/ → /s/. Acoustic analysis further revealed gradual separation in both acoustic dimensions, with the initial undifferentiated form ambiguous between /ɕ/ and /ʂ/. Conclusions: The observed sound-acquisition order was interpreted as reflecting a combined influence of both oromotor maturation and language-specific phoneme frequency in Putonghua. Acoustic results suggest a maturational advantage of the tongue body over the tongue tip during fricative development.