Development of the voiceless sibilant fricative contrast in three-year-olds: an ultrasound and acoustic study.

The study analysed spectral and tongue shape dynamics of voiceless alveolar and postalveolar fricatives produced by ten children learning Scottish English. Synchronised ultrasound tongue imaging data and acoustic data were used to characterise children's productions of the phonemic contrast. Six children had consistently accurate productions of both fricative targets, with some cross-consonant phonetic differences in the direction previously demonstrated for older children and adults, as well as some immature acoustic and articulatory dynamic patterns. Instrumental analyses made it possible to describe tongue shape for phonemic errors and phonetically distorted realisations. There was some evidence of articulatory contrast in production preceding contrast in perception. The observed patterns can be explained by the complex articulatory demands on the fricative production, in combination with the developing control of articulators. The paper concludes by discussing the implications of the results for phonological theory and for speech therapy practice.

The Impact of Real-Time Articulatory Information on Phonetic Transcription: Ultrasound-Aided Transcription in Cleft Lip and Palate Speech.

OBJECTIVE: This study investigated whether adding an additional modality, namely ultrasound tongue imaging (UTI), to perception-based phonetic transcription impacted on the identification of compensatory articulations and on interrater reliability. PATIENTS AND METHODS: Thirty-nine English-speaking children aged 3-12 years with cleft lip and palate (CLP) were recorded producing repetitions of /aCa/ for all places of articulation with simultaneous audio recording and probe-stabilized ultrasound (US). Three types of transcriptions were performed: (1) descriptive observations from the live US by the clinician recording the data, (2) US-aided transcription (UA) by two US-trained clinicians, and (3) traditional phonetic transcription by two CLP specialists from audio recording. We compared the number of consonants identified as in error by each transcriber and then classified errors into eight different subcategories. RESULTS: Both UA and traditional transcription yielded similar error detection rates; however, these were significantly higher than the observations recorded live in the clinic. Interrater reliability for the US transcribers was substantial (κ = 0.65) compared to moderate (κ = 0.47) for the traditional transcribers. US transcribers were more likely to identify covert errors such as double articulations and retroflexion than the audio-only transcribers. CONCLUSION: UTI is a useful complement to traditional phonetic transcription for CLP speech.

The dynamics of voiceless sibilant fricative production in children between 7 and 13 years old: An ultrasound and acoustic study.

This study reports on dynamic tongue shape and spectral characteristics of sibilant fricatives /s/ and /ʃ/ in Scottish English speaking children aged between 7 and 13 years old. The sequences /əCa/ and /əCi/ were produced by 40 children, with ten participants in each age group, and two-year intervals between successive groups. Productions of the same sequences by ten adults were used for comparison with the children's data. Quantitative dynamic analyses were carried out on spectral information and on ultrasound imaging data on tongue shape. All age groups differentiated between the two consonants in the fricative centroid and in tongue shape. Vowel-on-consonant effects showed consonant-specific patterns across age groups without a consistent increase or decrease in the extent of coarticulation with increasing age. The extent of discriminability between the two fricatives increased with age on both acoustic and articulatory measures. Younger speakers were generally more variable than older speakers. Complementary findings from the centroid and tongue shape measures suggest that age-related differences are due to the ongoing maturation of controlling the tongue in coordination with other articulators, particularly the jaw, throughout childhood.

An Ultrasound Study of the Development of Lingual Coarticulation during Childhood.

BACKGROUND/AIMS: There is growing evidence that coarticulation development is protracted and segment-specific, and yet very little information is available on the changes in the extent of coarticulation across different phonemes throughout childhood. This study describes lingual coarticulatory patterns in 6 age groups of Scottish English-speaking children between 3 and 13 years old. METHODS: Vowelon-consonant anticipatory coarticulation was analysed using ultrasound imaging data on tongue shape from 4 consonants that differ in the degree of constraint, i.e., the extent of articulatory demand, on the tongue. RESULTS: Consonant-specific age-related patterns are reported, with consonants that have more demands on the tongue reaching adolescent-like levels of coarticulation in older age groups. Within-speaker variability in tongue shape decreases with increasing age. CONCLUSION: Reduced coarticulation in the youngest age group may be due to insufficient tongue differentiation. Immature patterns for lingual consonants in 5- to 11-year-olds are explained by the goal of producing the consonant target overriding the goal of coarticulating the consonant with the following vowel.

Voiceless alveolar stop coarticulation in typically developing 5-year-olds and 13-year-olds.

In this study, vowel-on-consonant lingual coarticulation at [t] closure offset was compared in 5-year-old children and 13-year-old adolescents. The study aimed to establish whether, by the end of the closure, children from the younger age group adjust the tongue shape to the following vowels to the same extent as adolescents. Ten 5-year-olds and ten 13-year-olds, all speakers of Scottish Standard English, produced [t]-vowel syllables with the vowels [i] and [a], in a carrier phrase. Measures of tongue shape based on midsagittal ultrasound imaging data were used to compare anticipatory coarticulation and within-speaker variability across groups. Both age groups changed the extent of tongue dorsum bunching in order to coarticulate the consonant with the following vowels. The 5-year-old children, unlike the adolescents, did not consistently modify the bunching location within the tongue curve to accommodate the tongue shape to that of the upcoming vowel. Token-to-token variability was significantly greater in the younger age group. The results suggest that vowel-on-[t] coarticulatory patterns produced by typically developing children are affected by the development of motor control, with articulatory constraints on the tongue limiting the extent of lingual coarticulation in 5-year-old children. The findings on typical coarticulation development are relevant for clinical practice, and they highlight the need for more detailed descriptions of how phonetic characteristics of speech sounds affect coarticulation throughout childhood.

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

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.

Ultrasound and acoustic analysis of sibilant fricatives in preadolescents and adults.

This study describes the production of sibilant fricatives /s/ and /∫/, comparing Scottish English speaking preadolescent children with adults. The materials were the sequences /əCa/ and /əCi/ produced by 15 adults and 15 children aged between 10 and 12 years old. Quantitative analyses were carried out on both spectral information and on ultrasound imaging data on tongue shape, taken from nine successive time points during the fricative. The two groups of speakers were very similar to each other in the articulatory and acoustic characteristics distinguishing the two fricatives. Age-related differences in the fricative centroid measure occurred at consonant-vowel boundaries, with lower values in the preadolescents. Within-speaker variability was mostly similar across age groups, with the exception of the fricative centroid for /∫/, which was significantly more variable in preadolescents than in adults. Throughout the consonant duration, both groups consistently differentiated between the two consonants in both the fricative centroid and in one measure of tongue shape.

Quantifying lingual coarticulation using ultrasound imaging data collected with and without head stabilisation.

Previous studies reporting the use of ultrasound tongue imaging with clinical populations have generally provided qualitative information on tongue movement. Meaningful quantitative measures for use in the clinic typically require the speaker's head to be stabilised in relation to a transducer, which may be uncomfortable, and unsuitable for young children. The objective of this study was to explore the applicability of quantitative measurements of stabilisation-free tongue movement data, by comparing ultrasound data collected from 10 adolescents, with and without head stabilisation. Several measures of tongue shape were used to quantify coarticulatory influence from two contrasting vowels on four different consonants. Only one of the measures was completely unaffected by the stabilisation condition for all the consonants. The study also reported cross-consonant differences in vowel-related coarticulatory effects. The implications of the findings for the theory of coarticulation and for potential applications of stabilisation-free tongue curve measurements in clinical studies are discussed.

Spatial and temporal lingual coarticulation and motor control in preadolescents.

PURPOSE In this study, the authors compared coarticulation and lingual kinematics in preadolescents and adults in order to establish whether preadolescents had a greater degree of random variability in tongue posture and whether their patterns of lingual coarticulation differed from those of adults. METHOD High-speed ultrasound tongue contour data synchronized with the acoustic signal were recorded from 15 children (ages 10-12 years) and 15 adults. Tongue shape contours were analyzed at 9 normalized time points during the fricative phase of schwa-fricative-/a/ and schwa-fricative-/i/ sequences with the consonants /s/ and /ʃ/. RESULTS There was no significant age-related difference in random variability. Where a significant vowel effect occurred, the amount of coarticulation was similar in the 2 groups. However, the onset of the coarticulatory effect on preadolescent /ʃ/ was significantly later than on preadolescent /s/, and also later than on adult /s/ and /ʃ/. CONCLUSIONS Preadolescents have adult-like precision of tongue control and adult-like anticipatory lingual coarticulation with respect to spatial characteristics of tongue posture. However, there remains some immaturity in the motor programming of certain complex tongue movements.

A normative-speaker validation study of two indices developed to quantify tongue dorsum activity from midsagittal tongue shapes.

This study reported adult scores on two measures of tongue shape, based on midsagittal tongue shape data from ultrasound imaging. One of the measures quantified the extent of tongue dorsum excursion, and the other measure represented the place of maximal excursion. Data from six adult speakers of Scottish Standard English without speech disorders were analyzed. The stimuli included a range of consonants in consonant-vowel sequences, with the vowels /a/ and /i/. The measures reliably distinguished between articulations with and without tongue dorsum excursion, and produced robust results on lingual coarticulation of the consonants. The reported data can be used as a starting point for collecting more typical data and for analyzing disordered speech. The measurements do not require head-to-transducer stabilization. Possible applications of the measures include studying tongue dorsum overuse in people with cleft palate, and typical and disordered development of coarticulation.

Using ultrasound to quantify tongue shape and movement characteristics.

Objective : Previous experimental studies have demonstrated abnormal lingual articulatory patterns characterizing cleft palate speech. Most articulatory information to date has been collected using electropalatography, which records the location and size of tongue-palate contact but not the tongue shape. The latter type of data can be provided by ultrasound. The present paper aims to describe ultrasound tongue imaging as a potential tool for quantitative analysis of tongue function in speakers with cleft palate. A description of the ultrasound technique as applied to analyzing tongue movements is given, followed by the requirements for quantitative analysis. Several measures are described, and example calculations are provided. Measures : Two measures aim to quantify overuse of tongue dorsum in cleft palate articulations. Crucially for potential clinical applications, these measures do not require head-to-transducer stabilization because both are based on a single tongue curve. The other three measures compare sets of tongue curves, with the aim to quantify the dynamics of tongue displacement, token-to-token variability in tongue position, and the extent of separation between tongue curves for different speech sounds. Conclusions : All measures can be used to compare tongue function in speakers with cleft palate before and after therapy, as well as to assess their performance against that in typical speakers and to help in selecting more effective treatments.

Coarticulation as an indicator of speech motor control development in children: an ultrasound study.

There are still crucial gaps in our knowledge about developmental paths taken by children to adult-like speech motor control. Mature control of articulators during speaking is manifested in the appropriate extent of coarticulation (the articulatory overlap of speech sounds). This study compared lingual coarticulatory properties of child and adult speech, using ultrasound tongue imaging. The participants were speakers of Standard Scottish English, ten adults and ten children aged 6-9 years. Consonant-vowel syllables were presented in a carrier phrase. Distances between tongue curves were used to quantify coarticulation. In both adults and children, vowel pairs /a/-/i/ and /a/-/u/ significantly affected the consonant, and the vowel pair /i/-/u/ did not. Extent of coarticulation was significantly greater in the children than in the adults, providing support for the notion that children's speech production operates with larger units than adults'. More within-speaker variability was found in the children than in the adults.

Adult speakers' tongue-palate contact patterns for bilabial stops within complex clusters.

Previous studies using Electropalatography (EPG) have shown that individuals with speech disorders sometimes produce articulation errors that affect bilabial targets, but currently there is limited normative data available. In this study, EPG and acoustic data were recorded during complex word final /sps/ clusters spoken by 20 normal adults. A total contact (TC) index measured amount of tongue-palate contact during clusters in words such as 'crisps'. Bilabial closure was inferred from the acoustic signal. The TC profiles indicated that normal adults hold their tongues in a steady /s/-like position throughout the cluster; most speakers (85%, n=17) had no significant difference in TC values during bilabial closure compared to flanking fricatives. The results are interpreted as showing that normal speakers produce double bilabial-alveolar articulations for /p/ in these clusters. Although steady state TC profiles were typical of the group, absolute TC values varied considerably between speakers, with some speakers having up to three times more contact than others. These findings add to the knowledge about normal articulation, and will help to improve diagnosis and treatment of individuals with speech disorders.