An acoustic-articulatory description of children's defective /s/ productions.

The /s/ production of six /s/-defective children and two normal controls were subjected to spectrographic analysis. Articulatorily, two of the children were dentalizers, two had lateral emission of friction, and two were of an "other" type. Results show for normals an /s/ spectrum which is compact (5-11 kHz), powerful, and dominated by strong, sharp spectral peaks at 6 and 10 kHz. Their spectra were context sensitive. Dental subjects showed flatter, less peaked, higher frequency (6-12 kHz), and less intense noise spectrum, which was not so context sensitive. Lateral /s/ subjects showed a broad 4-9 or 4-10 kHz spectrum characterized by somewhat smaller, more numerous peaks, and a lower cutoff frequency (about 4kHz) than for normals. The "other /s/ defectives varied very widely, so that no consistent pattern emerged. The acoustic data are then discussed in terms of the articulation of varieties of friction noise.