Previous articulatory studies have shown that speech motor development is protracted, and that even teenagers differ from adults in some aspects of speech production. In this talk I will present ultrasound imaging data on tongue movement throughout the consonant /s/ in the syllables /si/ and /sa/, in adults and children aged between 10 and 12 years old, native speakers of Standard Scottish English. Synchronised ultrasound and acoustic data were recorded, with six repetitions of /si/ and /sa/ in a carrier phrase. The ultrasound frame rate was 100 Hz.
Tongue movement over the consonant was traced in every frame, and distances between tongue curves were computed. The consonant duration was also measured. The following questions will be addressed:
What distance does the tongue travel during /s/ in /si/ and during /s/ in /sa/, and is there an age-related difference? Does the rate of tongue movement change throughout /s/, and do children and adults have different patterns? At what point, during /s/, are the tongue shapes differentiated according to the two vowel contexts? Finally, are children more variable than adults, in space and time?
Children under the age of ten have been found not to differentiate between tongue shapes at mid-/s/ in /sV/ syllables with contrasting vowels, while adults have been shown to make this distinction at mid-/s/. It is hypothesised that in adults, vowel-related difference between consonant tongue shapes will be observed at least at mid-/s/, and that in children, this difference will become apparent later than mid-/s/. Consistent with the literature on speech development, greater within-speaker variability is expected for children than for adults.