Using ultrasound tongue imaging to identify covert contrasts in children’s speech

ABSTRACT

Ultrasound tongue imaging has become a promising technique for detecting covert contrasts, due to the developments in data analysis methods that allow for processing information on tongue shape from young children. An important feature concerning analyses of ultrasound data from children who are likely to produce covert contrasts is that the data are likely to be collected without head-to-transducer stabilisation, due to the speakers’ age. This article is a review of the existing methods applicable in analysing data from non-stabilised recordings. The article describes some of the challenges of ultrasound data collection from children, and analysing these data, as well as possible ways to address those challenges. Additionally, there are examples from typical and disordered productions featuring covert contrasts, with illustrations of quantifying differences in tongue shape between target speech sounds.

KEYWORDS:

• Covert contrasts
• child
• lingual articulation
• speech production measurement
• subtle differences
• ultrasound

Declaration of interest

The authors report no conflicts of interest.

Funding

This work was supported by a grant from the Economic and Social Research Council (ES/K002597/1).

Notes

¹ Compare these measures with another way of quantifying tongue curvature, reported in Stone et al. (1987), who used the origin of the ultrasound image, i.e. a transducer-based landmark, as a reference point for curvature calculations using tongue contours from adults’ productions. With the reference point for measurements being external to the vocal tract, if such measurements were applied to young children’s productions, the values would likely be affected by children’s head movements in relation to the transducer during the recording.

² Perceptual similarity was assessed by each of the three authors individually by listening to audio recordings of the realisations of the carrier sentences containing the target consonant-vowel syllables. There was no fixed order of presentation of the three sentences, and no limitation on the number of times that the stimuli could be played back. The task was to determine whether the three target consonants sounded the same to each other, or whether there were any audible differences.

Additional information

Funding

This work was supported by a grant from the Economic and Social Research Council (ES/K002597/1).