Development of [j] in young, midwestern, American children

Production of the English /ɹ/ by Mandarin-English Bilingual Speakers

Rhotic sounds are some of the most challenging sounds for L2 learners to acquire. This study investigates the production of English rhotic sounds by Mandarin-English bilinguals with two English proficiency levels. The production of the English /ɹ/ by 17 Mandarin-English bilinguals was examined with ultrasound imaging and compared with the production of native English speakers. The ultrasound data show that bilinguals can produce native-like bunched and retroflex gestures, but the distributional pattern of tongue shapes in various contexts differs from that of native speakers. Acoustically, the English /ɹ/ produced by bilinguals had a higher F3 and F3-F2, as well as some frication noise in prevocalic /ɹ/, features similar to the Mandarin /ɹ/. Mandarin-English bilinguals did produce language-specific phonetic realizations for the English and Mandarin /ɹ/s. There was a positive correlation between language proficiency and English-specific characteristics of /ɹ/ by Mandarin-English bilinguals in both articulation and acoustics. Phonetic similarities facilitated rather than hindered L2 speech learning in production: Mandarin-English bilinguals showed better performance in producing the English /ɹ/ allophones that were more similar to the Mandarin /ɹ/ (syllabic and postvocalic /ɹ/s) than producing the English /ɹ/ allophone that was less similar to the Mandarin /ɹ/ (prevocalic /ɹ/). This study contributes to our understanding of the mechanism of speech production in late bilinguals.

Traditional and Visual-Acoustic Biofeedback Treatment via Telepractice for Residual Speech Sound Disorders Affecting /ɹ/: Pilot study

Purpose

This study aimed to examine the feasibility of telepractice delivery of a treatment package including visual-acoustic biofeedback and motor-based treatment for residual speech sound disorder affecting /ɹ/ in school-age children. The overall study used a single-case randomization design; however, this preliminary report will simply quantify changes in accuracy before and after completion of the treatment package. The present analysis did not differentiate between the relative contributions of biofeedback and motor-based treatments.

Method

Seven children aged 9-14 received speech therapy for /ɹ/ distortions via telepractice. The study design consisted of three phases: baseline (four sessions), treatment (20 sessions), and post-treatment (three sessions). Treatment included two sessions weekly for a duration of 10 weeks. The participants received one motor-based/non-biofeedback session and one visual-acoustic biofeedback session per week. The order of treatment within each week was randomly determined prior to the start of therapy. Overall progress was assessed using untrained listeners' ratings of word probes administered in the baseline and posttreatment phases.

Results

Findings revealed that six of the seven participants showed a clinically significant response to the overall treatment package, although the magnitude of individual responses varied across speech contexts (consonantal and vocalic) and participants.

Conclusion

The present results suggest that a treatment combining visual-acoustic biofeedback and motor-based treatment for residual /ɹ/ errors treatment can be effectively delivered via telepractice. Considerations for technology setup and treatment protocols are provided.

Positional asymmetries in consonant production and intelligibility in dysarthric speech

Consonant production errors are common in dysarthric speech, but not all consonants are affected to the same extent. Currently, only limited knowledge exists regarding whether different positional allophones are affected to varying degrees in dysarthric speech. The aim of this study was to investigate the effect of consonants' position-in-words on consonant production accuracy and their relevance to speech intelligibility. To this end, the percentage of correctly articulated consonants was analyzed with respect to position-in-words, manner of articulation, and speakers' overall intelligibility in dysarthric speech secondary to cerebral palsy. Results revealed that consonants were generally more accurate in initial positions than other positions, and when they were singletons rather than clusters. However, fricatives, a category commonly noted for frequent misarticulations, exhibited no significant positional effects, indicating that fricatives were affected to a similar degree across all word positions. In addition, positional asymmetry manifested to a greater degree as intelligibility decreased. Finally, the strength of the relationship between consonant production accuracy and intelligibility varied depending on positions-in-words, with strong correlations in the medial and final cluster positions but no significant correlation for fricatives in the initial and final singleton positions. The correlation was markedly low for the initial consonants, possibly due to the resistance of initial consonants to production errors. The positional asymmetry found in this study necessitates more research on non-initial consonants and clusters for their potential in improving consonant production and speech intelligibility as a part of dysarthria management.

Tutorial: Using Visual-Acoustic Biofeedback for Speech Sound Training

PURPOSE

This tutorial summarizes current practices using visual-acoustic biofeedback (VAB) treatment to improve speech outcomes for individuals with speech sound difficulties. Clinical strategies will focus on residual distortions of /ɹ/.

METHOD

Summary evidence related to the characteristics of VAB and the populations that may benefit from this treatment are reviewed. Guidelines are provided for clinicians on how to use VAB with clients to identify and modify their productions to match an acoustic representation. The clinical application of a linear predictive coding spectrum is emphasized.

RESULTS

Successful use of VAB requires several key factors including clinician and client comprehension of the acoustic representation, appropriate acoustic target and template selection, as well as appropriate selection of articulatory strategies, practice schedules, and feedback models to scaffold acquisition of new speech sounds.

CONCLUSION

Integrating a VAB component in clinical practice offers additional intervention options for individuals with speech sound difficulties and often facilitates improved speech sound acquisition and generalization outcomes.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21817722.

Does Early Phonetic Differentiation Predict Later Phonetic Development? Evidence From a Longitudinal Study of /ɹ/ Development in Preschool Children

Purpose We evaluated whether children whose inaccurate /ɹ/ productions showed evidence phonetic differentiation with /w/ at 3.5-4.5 years of age improved in /ɹ/ production over the next year more than children whose inaccurate productions did not show evidence of such differentiation. We also examined whether speech perception, inhibitory control, and vocabulary size predicted growth in /ɹ/. Method A set of typically developing, monolingual English-speaking preschool children (n = 136) produced tokens of /ɹ/- and /w/-initial words at two time points (TPs), at which they were 39-52 and 51-65 months old. Children's productions of /ɹ/ and /w/ were narrowly phonetically transcribed. Children's productions at the earlier time point were rated by naïve listeners using a visual analog scale measure of phoneme goodness; these ratings were used to assess the degree of phonetic differentiation between /ɹ/ and /w/. Results Accuracy for both phonemes varied considerably at both TPs. The growth in accuracy of /ɹ/ between the two TPs was not predicted by any individual-differences measures, nor by the degree of differentiation between /ɹ/ and /w/at the earlier time point. Conclusion Low vocabulary size, low inhibitory control, poor speech perception, and the absence of early phonetic differentiation are not necessarily limiting factors in predicting /ɹ/ growth in individual children in the age range we studied.

The Acquisition of Articulatory Timing for Liquids: Evidence From Child and Adult Speech

Purpose Liquids are among the last sounds to be acquired by English-speaking children. The current study considers their acquisition from an articulatory timing perspective by investigating anticipatory posturing for /l/ versus /ɹ/ in child and adult speech. Method In Experiment 1, twelve 5-year-old, twelve 8-year-old, and 11 college-aged speakers produced carrier phrases with penultimate stress on monosyllabic words that had /l/, /ɹ/, or /d/ (control) as singleton onsets and /æ/ or /u/ as the vowel. Short-domain anticipatory effects were acoustically investigated based on schwa formant values extracted from the preceding determiner (= the) and dynamic formant values across the /ə#LV/ sequence. In Experiment 2, long-domain effects were perceptually indexed using a previously validated forward-gated audiovisual speech prediction task. Results Experiment 1 results indicated that all speakers distinguished /l/ from /ɹ/ along F3. Adults distinguished /l/ from /ɹ/ with a lower F2. Older children produced subtler versions of the adult pattern; their anticipatory posturing was also more influenced by the following vowel. Younger children did not distinguish /l/ from /ɹ/ along F2, but both liquids were distinguished from /d/ in the domains investigated. Experiment 2 results indicated that /ɹ/ was identified earlier than /l/ in gated adult speech; both liquids were identified equally early in 5-year-olds' speech. Conclusions The results are interpreted to suggest a pattern of early tongue-body retraction for liquids in /ə#LV/ sequences in children's speech. More generally, it is suggested that children must learn to inhibit the influence of vowels on liquid articulation to achieve an adultlike contrast between /l/ and /ɹ/ in running speech.

Assessing Rhotic Production by Bilingual Spanish Speakers

Due to its articulatory precision, the Spanish rhotic system is generally acquired in late childhood by monolingually-raised (L1) Spanish speakers. Heritage speakers and second language (L2) learners, unlike L1 speakers, risk an incomplete acquisition of the rhotic system due to limited Spanish input and possible phonological interference from English. In order to examine the effects of age of onset of bilingualism and cross-linguistic influence on bilinguals’ rhotic productions, twenty-four adult participants (six sequential bilingual heritage speakers, six simultaneous bilingual heritage speakers, six L1 Spanish speakers, six L2 Spanish learners) were audio recorded in a storytelling task and a picture naming task. The alveolar taps [ɾ] and alveolar trills [r] produced in these tasks were examined according to duration of the rhotic sound and number of apical occlusions. Results showed that the sequential bilinguals, but not the simultaneous bilinguals or the L2 learners, patterned similarly to the L1 Spanish speakers in their production of taps and trills. Neither heritage group produced the English alveolar approximant [ɹ]; the L2 learners, on the other hand, did produce [ɹ] when speaking Spanish. The results of this study suggest that early language input can affect the production of sounds that are acquired in late childhood.

Effects of Practice Variability on Second-Language Speech Production Training

BACKGROUND

Mastering the phonetics of a second language (L2) involves a component of speech-motor skill, and it has been suggested that L2 learners aiming to achieve a more native-like pronunciation could benefit from practice structured in accordance with the principles of motor learning.

PARTICIPANTS AND METHODS

This study investigated the influence one such principle, high versus low variability in practice, has on speech-motor learning for Korean adults seeking to acquire native-like production of English rhotics. Practice incorporated a commercially available intraoral placement device ("R Buddy," Speech Buddies Inc.). In a single-subject across-behaviors design, 8 participants were pseudorandomly assigned to practice rhotic targets in a low-variability (single word) or high-variability (multiple words) practice condition.

RESULTS

The hypothesized advantage for high-variability over low-variability practice was observed in the short-term time frame. However, long-term learning was limited in nature for both conditions.

CONCLUSION

These results suggest that future research should incorporate high-variability practice while identifying additional manipulations to maximize the magnitude of long-term generalization learning.

Acquisition of Pitjantjatjara Clause Chains

In Pitjantjatjara, a central Australian Indigenous language, speakers typically describe sequences of actions using clause chaining constructions. While similar constructions are common among the world’s languages, very little is known about how children acquire them. A notable exception are the converb constructions of Turkish, which have been relatively well-studied. The present paper examines the acquisition of Pitjantjatara clause chaining constructions and compares this with the acquisition of Turkish converb constructions. Data is drawn from a naturalistic corpus recorded between 2016 and 2019. The corpus contains over 4000 utterances from 23 children aged between 10 months and 10 years, five of whom are recorded at multiple ages. The corpus also includes approximately 1600 utterances from 21 adults, aged between 16 and 70. Results show that the acquisition of Pitjantjatjara clause chains consists of three stages. Stage 1 features juxtaposition of finite verb forms. In Stage 2, children make regular use of clause chain morphology, but primarily for modification purposes. In Stage 3, clause chains are the preferred strategy for sequential actions as well as modification purposes. The initial use of verb juxtaposition followed by increasing use of dedicated morphology is consistent with findings for Turkish converb acquisition, with speakers of both languages utilizing dedicated forms from around 2;6 onwards. A notable difference between the acquisition of Pitjantjatjara clause chains and Turkish converbs is in the order of acquisition of semantic functions. In Turkish, children acquire temporal functions, such as sequential actions, before modifying functions, such as manner specification. In Pitjantjatjara, the order is reversed, with children first using clause chaining constructions for modification and simultaneous aspects of events before utilizing them to combine sequential actions. This raises questions regarding the distribution and relative timing of event combination and modification strategies.

Acoustic Characteristics of Rhotic Vowel Productions of Young Children

AIMS

This study examined the acoustic characteristics of perceptually acceptable rhotic vowels produced by young children with and without speech sound disorders (SSDs). Productions were analyzed in relation to the overall rhotic proficiency level of each child, as determined by rhotic vowel and consonant accuracy. The effect of the surrounding phonetic contexts on acoustic realization of rhotic vowels was also examined.

METHODS

Participants included 18 children aged 2-6 years with and without SSD, grouped by overall rhotic sound proficiency (high rhotic proficiency: ≥70% correct rhotic consonants and vowels; intermediate rhotic proficiency: ≤30% correct rhotic consonants, but ≥70% correct rhotic vowels; low rhotic proficiency: ≤30% correct rhotic consonants and vowels). Target sounds included stressed and unstressed rhotic monophthongs ([ɝ] and [ɚ], respectively) and 4 rhotic diphthongs that differ by pre-rhotic vowel type (/ɪ͡ɚ/, /ɛ͡ɚ/, /ɔ͡ɚ/, /ɑ͡ɚ/). F3 and F3-F2 measures were compared across groups and contexts.

RESULTS

No significant differences in F3 and F3-F2 by rhotic sound proficiency group were found in rhotic vowels produced by children with above 70% rhotic vowel accuracy, regardless of their proficiency with rhotic consonants. Acoustic patterns differed by phonetic contexts, but the effect varied by rhotic sound proficiency group.

CONCLUSION

Results showed that once children learn to produce rhotic vowels, they show a comparable degree of rhoticity as those produced by children with high rhotic vowel and consonant accuracy. Results also suggest that rhotic sounds develop earlier in certain phonetic contexts than in others (e.g., [ɝ] before [ɚ]; /ɪ͡ɚ/ and /ɑ͡ɚ/ before /ɔ͡ɚ/).

An acoustic analysis of American English liquids by adults and children: Native English speakers and native Japanese speakers of English

This study investigated acoustic characteristics of American English liquids produced by native English (NE) and native Japanese (NJ) speakers reported in Aoyama, Flege, Guion, Akahane-Yamada, and Yamada [(2004). J. Phonetics 32, 233-250]. For a larger longitudinal study, the data were collected twice to investigate the acquisition of American English by the NJ speakers (Time 1, Time 2). Aoyama, Flege, Guion, Akahane-Yamada, and Yamada [(2004). J. Phonetics 32, 233-250] evaluated productions of /l/ and /ɹ/ in the NE and NJ adults and children (16 participants each) using NE speakers' perceptual judgments and showed that the NJ children's production of /ɹ/ improved from Time 1 to Time 2. In the current study, four acoustic parameters (duration, F1, F2, and F3) were measured in 256 tokens each of English /l/ and /ɹ/. Results showed that some acoustic parameters, such as F2, changed from Time 1 to Time 2 in the NJ speakers' productions, indicating improvements. However, the NJ speakers' productions were different from the NE speakers' productions in almost all acoustic parameters at both Time 1 and Time 2. Results suggest that the improvements in the NJ children's productions of /ɹ/ reported in Aoyama, Flege, Guion, Akahane-Yamada, and Yamada [(2004). J. Phonetics 32, 233-250] were due to a combination of changes, not due to a change in one acoustic parameter such as F3 in /ɹ/.

Starting to Talk at Age 10 Years: Lessons About the Acquisition of English Speech Sounds in a Rare Case of Severe Congenital But Remediated Motor Disease of Genetic Origin

Purpose This study was conducted to observe speech development in a child whose onset of oral communication was extremely delayed. In rare cases, children are born with physical limitations that temporarily interfere with speech sound production. Whether the development of speech sound production follows the same trajectory as that in typical children at younger ages is not well understood. Method We present a child who was wheelchair-bound and communicated nearly exclusively via augmentative and alternative communication devices due to severe congenital motor disease and generalized hypotonia. At age 10 years, her condition improved dramatically with medication after a mutation in a dopamine-related gene was discovered, and she switched entirely to oral communication. Observation of speech development was based on chart reviews, video recordings, and direct testing at age 15 years. Results At age 4 years, the participant's attempts at speech showed a small phoneme inventory consisting of early-acquired phonemes and large numbers of common phonological processes. Following the medical intervention at age 10 years, mastery of velars occurred after age 12 years and mastery of liquids was still incomplete at age 15 years. Conclusions Findings are consistent with general growth trends in speech sound acquisition that are independent of chronological age. Theoretical considerations regarding the role of motor control in the invariant order of speech sound acquisition are posited, specifically regarding articulatory building blocks. Clinical recommendations include interprofessional management of children with complex motor disease and referrals to genetics professionals in the care of such children.

Remediating Residual Rhotic Errors With Traditional and Ultrasound-Enhanced Treatment: A Single-Case Experimental Study

Purpose The aim of the study was to examine how ultrasound visual feedback (UVF) treatment impacts speech sound learning in children with residual speech errors affecting /ɹ/. Method Twelve children, ages 9-14 years, received treatment for vocalic /ɹ/ errors in a multiple-baseline across-subjects design comparing 8 sessions of UVF treatment and 8 sessions of traditional (no-biofeedback) treatment. All participants were exposed to both treatment conditions, with order counterbalanced across participants. To monitor progress, naïve listeners rated the accuracy of vocalic /ɹ/ in untreated words. Results After the first 8 sessions, children who received UVF were judged to produce more accurate vocalic /ɹ/ than those who received traditional treatment. After the second 8 sessions, within-participant comparisons revealed individual variation in treatment response. However, group-level comparisons revealed greater accuracy in children whose treatment order was UVF followed by traditional treatment versus children who received the reverse treatment order. Conclusion On average, 8 sessions of UVF were more effective than 8 sessions of traditional treatment for remediating vocalic /ɹ/ errors. Better outcomes were also observed when UVF was provided in the early rather than later stages of learning. However, there remains a significant individual variation in response to UVF and traditional treatment, and larger group-level studies are needed. Supplemental Material https://doi.org/10.23641/asha.8206640.

Rhotic vowel accuracy and error patterns in young children with and without Speech Sound Disorders

Rhotic vowels are known to be difficult sounds for children to learn, but their acquisition has not been investigated in detail. This study examined rhotic vowel development, including accuracy and error patterns, in young children across age, diagnostic groups, and phonetic contexts. Participants included 34 children from 2 to 6 years of age with and without speech sound disorders (SSD). Data included 36 elicited single words containing stressed and unstressed rhotic monophthongs ([ɜ˞] and [ə˞]) and four rhotic diphthongs (/ɪ͡ə˞/, /ε͡ə˞/, /ɔ͡ə˞/, and /ɑ͡ə˞/). Additional words containing non-rhotic vowels and the consonant /ɹ/ were also included for comparison. A significant difference in rhotic vowel production accuracy was found between diagnostic groups (with vs. without SSD), but not across age groups or phonetic contexts. Yet, the accuracy scores for children without SSD were bimodally distributed, showing overlapping patterns with children with SSD. Error patterns were examined for all children with low rhotic vowel accuracy scores, regardless of age and diagnostic status. Results of this study highlight the variability in rhotic vowel development in young children and the importance of studying rhotic sounds using overall rhotic sound accuracy of each individual child regardless of their age or diagnostic status. Clinically, systematic within-speaker error patterns suggest the need for the detailed error pattern assessment of rhotic sounds.

Selecting an acoustic correlate for automated measurement of American English rhotic production in children

Purpose: A current need in the field of speech-language pathology is the development of reliable and efficient techniques to evaluate accuracy of speech targets over the course of treatment. As acoustic measurement techniques improve, it should become possible to use automated scoring in lieu of ratings from a trained clinician in some contexts. This study asks which acoustic measures correspond most closely with expert ratings of children's productions of American English /ɹ/ in an effort to develop an automated scoring algorithm for use in treatment targeting rhotics. Method: A series of ordinal mixed-effects regression models were fit over a large sample of children's productions of words containing /ɹ/ that had previously been rated by three trained clinicians. Akaike/Bayesian Information Criteria were used to select the best-fitting model. Result: Controlling for age, sex, and allophonic contextual differences, the measure that accounted for the most variance in speech rating was F3-F2 distance normalised relative to a sample of age- and sex-matched speakers. Conclusion: We recommend this acoustic measure for use in future automated scoring of children's production of American English rhotics. We also suggest that computer-based treatment with automated scoring should facilitate increases in treatment dosage by improving options for home practice.

Modelling category goodness judgments in children with residual sound errors

This study investigates category goodness judgments of /r/ in adults and children with and without residual speech errors (RSEs) using natural speech stimuli. Thirty adults, 38 children with RSE (ages 7-16) and 35 age-matched typically developing (TD) children provided category goodness judgments on whole words, recorded from 27 child speakers, with /r/ in various phonetic environments. The salient acoustic property of /r/ - the lowered third formant (F3) - was normalized in two ways. A logistic mixed-effect model quantified the relationships between listeners' responses and the third formant frequency, vowel context and clinical group status. Goodness judgments from the adult group showed a statistically significant interaction with the F3 parameter when compared to both child groups (p < 0.001) using both normalization methods. The RSE group did not differ significantly from the TD group in judgments of /r/. All listeners were significantly more likely to judge /r/ as correct in a front-vowel context. Our results suggest that normalized /r/ F3 is a statistically significant predictor of category goodness judgments for both adults and children, but children do not appear to make adult-like judgments. Category goodness judgments do not have a clear relationship with /r/ production abilities in children with RSE. These findings may have implications for clinical activities that include category goodness judgments in natural speech, especially for recorded productions.

Articulation Speaks to Executive Function: An Investigation in 4- to 6-Year-Olds

Executive function (EF) and language learning play a prominent role in early childhood development. Empirical research continues to point to a concurrent relation between these two faculties. What has been given little attention, however, is the association between EF and speech articulation abilities in children. This study investigated this relation in children aged 4-6 years. Significant correlations indicated that children with better EF [via parental report of the Behavior Rating Inventory of Executive Function (BRIEF) inventory] exhibited stronger speech sound production abilities in the articulation of the "s" and "sh" sounds. Furthermore, regression analyses revealed that the Global Executive Composite (GEC) of EF as measured by the BRIEF, served as a predictor for speech sound proficiency and that speech sound proficiency served as a predictor for the GEC. Together, these results demonstrate the imbricated nature of EF and speech sound production while bearing theoretical and practical implications. From a theoretical standpoint, the close link between EF and speech articulation may indicate a common ontogenetic pathway. From a practical perspective, the results suggest that children with speech difficulties could be at higher risk for EF deficits.

Efficacy of Electropalatography for Treating Misarticulation of /r/

PURPOSE

The purpose of the present study was to document the efficacy of electropalatography (EPG) for the treatment of rhotic errors in school-age children. Despite a growing body of literature using EPG for the treatment of speech sound errors, there is little systematic evidence about the relative efficacy of EPG for rhotic errors.

METHOD

Participants were 5 English-speaking children aged 6;10 to 9;10, who produced /r/ at the word level with < 30% accuracy but otherwise showed typical speech, language, and hearing abilities. Therapy was delivered in twice-weekly 30-min sessions for 8 weeks.

RESULTS

Four out of 5 participants were successful in achieving perceptually and acoustically accurate /r/ productions during within-treatment trials. Two participants demonstrated generalization of /r/ productions to nontreated targets, per blinded listener ratings.

CONCLUSIONS

The present findings support the hypothesis that EPG can improve production accuracy in some children with rhotic errors. However, the utility of EPG is likely to remain variable across individuals. For rhotics, EPG training emphasizes one possible tongue configuration consistent with accurate rhotic production (lateral tongue contact). Although some speakers respond well to this cue, the narrow focus may limit lingual exploration of other acceptable tongue shapes known to facilitate rhotic productions.

Methods for eliciting, annotating, and analyzing databases for child speech development

Methods from automatic speech recognition (ASR), such as segmentation and forced alignment, have facilitated the rapid annotation and analysis of very large adult speech databases and databases of caregiver-infant interaction, enabling advances in speech science that were unimaginable just a few decades ago. This paper centers on two main problems that must be addressed in order to have analogous resources for developing and exploiting databases of young children's speech. The first problem is to understand and appreciate the differences between adult and child speech that cause ASR models developed for adult speech to fail when applied to child speech. These differences include the fact that children's vocal tracts are smaller than those of adult males and also changing rapidly in size and shape over the course of development, leading to between-talker variability across age groups that dwarfs the between-talker differences between adult men and women. Moreover, children do not achieve fully adult-like speech motor control until they are young adults, and their vocabularies and phonological proficiency are developing as well, leading to considerably more within-talker variability as well as more between-talker variability. The second problem then is to determine what annotation schemas and analysis techniques can most usefully capture relevant aspects of this variability. Indeed, standard acoustic characterizations applied to child speech reveal that adult-centered annotation schemas fail to capture phenomena such as the emergence of covert contrasts in children's developing phonological systems, while also revealing children's nonuniform progression toward community speech norms as they acquire the phonological systems of their native languages. Both problems point to the need for more basic research into the growth and development of the articulatory system (as well as of the lexicon and phonological system) that is oriented explicitly toward the construction of age-appropriate computational models.

Deriving individualised /r/ targets from the acoustics of children's non-rhotic vowels

In visual-acoustic biofeedback for rhotic errors, learners are guided to match the third formant (F3) location to a visual target on a real-time acoustic spectrum. As the acoustic properties of correct English /r/differ across speakers, this study aimed to improve target selection by investigating the validity of individualised targets derived from children's non-rhotic vowels. A previously proposed prediction formula was adjusted using data from a child normative sample and tested in two groups of children. Study 1 found that predicted values were unexpectedly higher than actual F3 values in children whose /r/ errors had been remediated. To understand this discrepancy, Study 2 applied the formula to typically developing children and found that predicted values were also higher than actual F3 values, suggesting that different normative data might better represent the current samples. An updated formula is proposed, which can be used to generate individualised targets within acoustic biofeedback applications.

Efficacy of Visual-Acoustic Biofeedback Intervention for Residual Rhotic Errors: A Single-Subject Randomization Study

PURPOSE

This study documented the efficacy of visual-acoustic biofeedback intervention for residual rhotic errors, relative to a comparison condition involving traditional articulatory treatment. All participants received both treatments in a single-subject experimental design featuring alternating treatments with blocked randomization of sessions to treatment conditions.

METHOD

Seven child and adolescent participants received 20 half-hour sessions of individual treatment over 10 weeks. Within each week, sessions were randomly assigned to feature traditional or biofeedback intervention. Perceptual accuracy of rhotic production was assessed in a blinded, randomized fashion. Each participant's response to the combined treatment package was evaluated by using effect sizes and visual inspection. Differences in the magnitude of response to traditional versus biofeedback intervention were measured with individual randomization tests.

RESULTS

Four of 7 participants demonstrated a clinically meaningful response to the combined treatment package. Three of 7 participants showed a statistically significant difference between treatment conditions. In all 3 cases, the magnitude of within-session gains associated with biofeedback exceeded the gains associated with traditional treatment.

CONCLUSIONS

These results suggest that the inclusion of visual-acoustic biofeedback can enhance the efficacy of intervention for some individuals with residual rhotic errors. Further research is needed to understand which participants represent better or poorer candidates for biofeedback treatment.

Perception-production relations in later development of American English rhotics

It is known that some adult listeners have more sharply defined perceptual categories than others, and listeners with more precise auditory targets are also more precise in their production of contrasts. There is additionally evidence that children who have not yet mastered production of a contrast show diminished performance on perceptual measures of the same contrast. To date, however, few studies have investigated developmental perception-production relations using the fine-grained measures typical of adult studies. Existing evidence suggests that perception and production can be closely connected in development, but this relationship may break down as perception and articulation mature at different rates. This study evaluated perception and production of the English /r-w/ contrast in 40 typically-developing children aged 9-14. Perceptual sensitivity was measured with a logistic function fitted over responses in a forced-choice identification task using two synthetic 10-step continua from rake to wake. Participants also produced rhotic and non-rhotic words. Across participants, there was a significant correlation between perceptual acuity and rhoticity in production, although this effect was only observed for one of two continua tested. These results provide preliminary evidence compatible with the hypothesis that children with a more refined auditory target for a sound also produce that sound more accurately.

Motor-based treatment with and without ultrasound feedback for residual speech-sound errors

BACKGROUND

There is a need to develop effective interventions and to compare the efficacy of different interventions for children with residual speech-sound errors (RSSEs). Rhotics (the r-family of sounds) are frequently in error American English-speaking children with RSSEs and are commonly targeted in treatment. One treatment approach involves the use of ultrasound visual feedback of the tongue.

AIMS

Although prior studies have shown that children with RSSEs acquire rhotics and generalize to untrained words with ultrasound visual feedback treatment, predictions from schema-based motor learning theory suggest that visual feedback might impede generalization. Therefore, the primary aim was to compare the generalization of rhotics treated with and without ultrasound in children with RSSEs.

METHODS & PROCEDURES

Twelve children aged 10-16 years with RSSEs affecting rhotics participated in a multiple-baseline single-case design with two treatment phases. For each participant, rhotics in one syllable position were treated for 7 h-long sessions with ultrasound visual feedback and rhotics in a different syllable position were treated without ultrasound in a second treatment phase. The order of treatment conditions was counterbalanced across participants. A treatment framework incorporating the principles of motor learning through chaining procedures was implemented across both treatment phases; thus the primary distinction between conditions was the use of ultrasound visual feedback.

OUTCOMES & RESULTS

On average, both treatments resulted in an approximately 30% increase in accuracy of untreated words in seven sessions. However, variability in response suggested some children showed a preferential response to one treatment over another, some responded well to both interventions, and some responded minimally to both interventions.

CONCLUSIONS & IMPLICATIONS

Motor-based treatment with and without ultrasound visual feedback of the tongue may aid in speech-sound acquisition for children with RSSEs. Both approaches may be viable options for some children. Future research is necessary to determine which children are the best candidates for interventions with and without ultrasound visual feedback.

Differential Effects of Visual-Acoustic Biofeedback Intervention for Residual Speech Errors

Recent evidence suggests that the incorporation of visual biofeedback technologies may enhance response to treatment in individuals with residual speech errors. However, there is a need for controlled research systematically comparing biofeedback versus non-biofeedback intervention approaches. This study implemented a single-subject experimental design with a crossover component to investigate the relative efficacy of visual-acoustic biofeedback and traditional articulatory treatment for residual rhotic errors. Eleven child/adolescent participants received ten sessions of visual-acoustic biofeedback and 10 sessions of traditional treatment, with the order of biofeedback and traditional phases counterbalanced across participants. Probe measures eliciting untreated rhotic words were administered in at least three sessions prior to the start of treatment (baseline), between the two treatment phases (midpoint), and after treatment ended (maintenance), as well as before and after each treatment session. Perceptual accuracy of rhotic production was assessed by outside listeners in a blinded, randomized fashion. Results were analyzed using a combination of visual inspection of treatment trajectories, individual effect sizes, and logistic mixed-effects regression. Effect sizes and visual inspection revealed that participants could be divided into categories of strong responders (n = 4), mixed/moderate responders (n = 3), and non-responders (n = 4). Individual results did not reveal a reliable pattern of stronger performance in biofeedback versus traditional blocks, or vice versa. Moreover, biofeedback versus traditional treatment was not a significant predictor of accuracy in the logistic mixed-effects model examining all within-treatment word probes. However, the interaction between treatment condition and treatment order was significant: biofeedback was more effective than traditional treatment in the first phase of treatment, and traditional treatment was more effective than biofeedback in the second phase. This is consistent with existing theory and data suggesting that detailed knowledge of performance feedback is most effective in the early stages of motor learning. Further research is needed to confirm that an initial phase of biofeedback has a facilitative effect, and to determine the optimal duration of biofeedback treatment. In addition, there is a strong need for correlational studies to examine which individuals with residual speech errors are most likely to respond to treatment.

Deriving gradient measures of child speech from crowdsourced ratings

Recent research has demonstrated that perceptual ratings aggregated across multiple non-expert listeners can reveal gradient degrees of contrast between sounds that listeners might transcribe identically. Aggregated ratings have been found to correlate strongly with acoustic gold standard measures both when individual raters use a continuous rating scale such as visual analog scaling (Munson et al., 2012) and when individual raters provide binary ratings (McAllister Byun, Halpin, & Szeredi, 2015). In light of evidence that inexperienced listeners use continuous scales less consistently than experienced listeners, this study investigated the relative merits of binary versus continuous rating scales when aggregating responses over large numbers of naive listeners recruited through online crowdsourcing. Stimuli were words produced by children in treatment for misarticulation of North American English /r/. Each listener rated the same 40 tokens two times: once using Visual Analog Scaling (VAS) and once using a binary rating scale. The gradient rhoticity of each item was then estimated using (a) VAS click location, averaged across raters; (b) the proportion of raters who assigned the "correct /r/" label to each item in the binary rating task (pˆ). First, we validate these two measures of rhoticity against each other and against an acoustic gold standard. Second, we explore the range of variability in individual response patterns that underlie these group-level data. Third, we integrate statistical, theoretical, and practical considerations to offer guidelines for determining which measure to use in a given situation.

Finding the experts in the crowd: Validity and reliability of crowdsourced measures of children's gradient speech contrasts

Perceptual ratings aggregated across multiple nonexpert listeners can be used to measure covert contrast in child speech. Online crowdsourcing provides access to a large pool of raters, but for practical purposes, researchers may wish to use smaller samples. The ratings obtained from these smaller samples may not maintain the high levels of validity seen in larger samples. This study aims to measure the validity and reliability of crowdsourced continuous ratings of child speech, obtained through Visual Analog Scaling, and to identify ways to improve these measurements. We first assess overall validity and interrater reliability for measurements obtained from a large set of raters. Second, we investigate two rater-level measures of quality, individual validity and intrarater reliability, and examine the relationship between them. Third, we show that these estimates may be used to establish guidelines for the inclusion of raters, thus impacting the quality of results obtained when smaller samples are used.

Perceptual, durational and tongue displacement measures following articulation therapy for rhotic sound errors

Outcomes of articulation therapy for rhotic errors are usually assessed perceptually. However, our understanding of associated changes of tongue movement is limited. This study described perceptual, durational and tongue displacement changes over 10 sessions of articulation therapy for /ɹ/ in six children. Four of the participants also received ultrasound biofeedback of their tongue shape. Speech and tongue movement were recorded pre-therapy, after 5 sessions, in the final session and at a one month follow-up. Perceptually, listeners perceived improvement and classified more productions as /ɹ/ in the final and follow-up assessments. The durations of VɹV syllables at the midway point of the therapy were longer. Cumulative tongue displacement increased in the final session. The average standard deviation was significantly higher in the middle and final assessments. The duration and tongue displacement measures illustrated how articulation therapy affected tongue movement and may be useful for outcomes research about articulation therapy.

Limited acquisition and generalisation of rhotics with ultrasound visual feedback in childhood apraxia

Ultrasound visual feedback of the tongue is one treatment option for individuals with persisting speech sound errors. This study evaluated children's performance during acquisition and generalisation of American English rhotics using ultrasound feedback. Three children aged 10-13 with persisting speech sound errors associated with childhood apraxia of speech (CAS) were treated for 14 one-hour sessions. Two of the participants increased the accuracy of their rhotic production during practise trials within treatment sessions, but none demonstrated generalisation to untreated words. Lack of generalisation may be due to a failure to acquire the target with sufficient accuracy during treatment, or to co-existing linguistic weaknesses that are not addressed in a motor-based treatment. Results suggest a need to refine the intervention procedures for CAS and/or a need to identify appropriate candidates for intervention to optimise learning.

The Articulatory Phonetics of /r/ for Residual Speech Errors

Effective treatment for children with residual speech errors (RSEs) requires in-depth knowledge of articulatory phonetics, but this level of detail may not be provided as part of typical clinical coursework. At a time when new imaging technologies such as ultrasound continue to inform our clinical understanding of speech disorders, incorporating contemporary work in the basic articulatory sciences into clinical training becomes especially important. This is particularly the case for the speech sound most likely to persist among children with RSEs-the North American English rhotic sound, /r/. The goal of this article is to review important information about articulatory phonetics as it affects children with RSE who present with /r/ production difficulties. The data presented are largely drawn from ultrasound and magnetic resonance imaging studies. This information will be placed in a clinical context by comparing productions of typical adult speakers to successful versus misarticulated productions of two children with persistent /r/ difficulties.

Children's acquisition of English onset and coda /l/: articulatory evidence

PURPOSE

The goal of this study was to better understand how and when onset /l/ (leap) and coda /l/ (peel) are acquired by children by examining both the articulations involved and adults' perceptions of the produced segments.

METHOD

Twenty-five typically developing Australian English-speaking children aged 3;0 (years;months) to 7;11 participated in an elicited imitation task, during which audio, video, and lingual ultrasound images were collected. Transcribers perceptually rated audio, whereas video and ultrasound images were visually examined for the presence of adult-like articulations.

RESULTS

Data from this study establish that for Australian English-learning children, coda /l/s are acquired later than onset /l/s, and older children produce greater proportions of adultlike /l/s in both onset and coda positions, roughly following established norms for American English-speaking children. However, although perceptibility of coda /l/s was correlated with their articulations, onset /l/s were nearly uniformly perceived as adultlike despite substantial variation in the articulations used to produce them.

CONCLUSIONS

The disparity in the production and perception of children's singleton onset /l/s is linked to both physiological and phonological development. Suggestions are made for future research to tease these factors apart.

Evidence for the distinction between "consonantal-/r/" and "vocalic-/r/" in American English

We examine the distinction between "consonantal-r" and "vocalic-r" in American English, terms encountered in the speech pathology literature but rarely in phonetic studies. We review evidence from phonetics, phonology and therapy, and describe our own study which measured percentage rhoticity in pre- and post-vocalic /r/. We suggest that the evidence supports a view that there is no more variation between pre-vocalic and post-vocalic /r/ than found in many other consonants. We also evaluate the different transcription traditions for post-vocalic /r/ in American English (as a consonant or a vowel), and describe a preliminary study demonstrating that these transcriptions are not equivalent, and denote different realisations.

Enhancing generalisation in biofeedback intervention using the challenge point framework: a case study

Biofeedback intervention can help children achieve correct production of a treatment-resistant error sound, but generalisation is often limited. This case study suggests that generalisation can be enhanced when biofeedback intervention is structured in accordance with a "challenge point" framework for speech-motor learning. The participant was an 11-year-old with residual /r/ misarticulation who had previously attained correct /r/ production through a structured course of ultrasound biofeedback treatment but did not generalise these gains beyond the word level. Treatment difficulty was adjusted in an adaptive manner following predetermined criteria for advancing, maintaining, or moving back a level in a multidimensional hierarchy of functional task complexity. The participant achieved and maintained virtually 100% accuracy in producing /r/ at both word and sentence levels. These preliminary results support the efficacy of a semi-structured implementation of the challenge point framework as a means of achieving generalisation and maintenance of treatment gains.

Retroflex versus bunched in treatment for rhotic misarticulation: evidence from ultrasound biofeedback intervention

PURPOSE

To document the efficacy of ultrasound biofeedback treatment for misarticulation of the North American English rhotic in children. Because of limited progress in the first cohort, a series of two closely related studies was conducted in place of a single study. The studies differed primarily in the nature of tongue-shape targets (e.g., retroflex, bunched) cued during treatment.

METHOD

Eight participants received 8 weeks of individual ultrasound biofeedback treatment targeting rhotics. In Study 1, all 4 participants were cued to match a bunched tongue-shape target. In Study 2, participants received individualized cues aimed at eliciting the tongue shape most facilitative of perceptually correct rhotics.

RESULTS

Participants in Study 1 showed only minimal treatment effects. In Study 2, all participants demonstrated improved production of rhotics in untreated words produced without biofeedback, with large to very large effect sizes.

CONCLUSIONS

The results of Study 2 indicate that with proper parameters of treatment, ultrasound biofeedback can be a highly effective intervention for children with persistent rhotic errors. In addition, qualitative comparison of Studies 1 and 2 suggests that treatment for the North American English rhotic should include opportunities to explore different tongue shapes, to find the most facilitative variant for each individual speaker.

Transcription-based and acoustic analyses of rhotic vowels produced by children with and without speech sound disorders: further analyses from the Memphis Vowel Project

The acquisition of rhotic monophthongs (/ɝ/ and /ɚ/) and diphthongs (/ɪ͡ɚ, ɛ͡ɚ, ɔ͡ɚ and ɑ͡ɚ/) was examined in 3- and 4-year-old children with and without speech sound disorders (SSDs), using both transcription-based and acoustic analyses. African-American (AA) and European-American (EA) participants (n = 40) with and without SSD were selected from archival data collected as part of the Memphis Vowel Project. Dialect variation influenced rhotic vowels differently for EA and AA children, thus their data were reported separately. Transcription-based analyses showed wide variation in the accuracy of different rhotic vowels. The most frequent error pattern for children with SSD was Derhoticization to a Back Rounded Vowel (e.g. /ɝ/ → [ʊ]; /ɪ͡ɚ/ → [ɪ͡о]). Rhotic diphthong reduction errors were less frequent; however, Coalesence (/ɑ͡ɚ/ → [ɔ]) was often observed for /ɑ͡ɚ/. F2, F3 and F3-F2 spectral movement patterns revealed differences between productions transcribed as correct and incorrect.

A multidimensional investigation of children's /r/ productions: perceptual, ultrasound, and acoustic measures

PURPOSE

This study explored relationships among perceptual, ultrasound, and acoustic measurements of children's correct and misarticulated /r/ sounds. Longitudinal data documenting changes across these parameters were collected from 2 children who acquired /r/ over a period of intervention and were compared with data from children with typical speech.

METHOD

Participants were 3 children with typical speech, recorded once, and 2 children with /r/ misarticulation, recorded over 7-8 months. The following data from /r/ produced in nonwords were collected: perceptually rated accuracy, ultrasound measures of tongue shape, and F3 - F2 distance.

RESULTS

Regression models revealed significant associations among perceptual, ultrasound, and acoustic measures of /r/ accuracy. The inclusion of quantitative tongue-shape measurements improved the match between the ultrasound and perceptual/acoustic data. Perceptually incorrect /r/ productions were found to feature posteriorly located peaked tongue shapes. Of the children who were seen longitudinally, 1 developed a bunched /r/ and 1 demonstrated retroflexion. The children with typical speech also differed in their tongue shapes.

CONCLUSION

Results support the validity of using qualitative and quantitative ultrasound measures to characterize the accuracy of children's /r/ sounds. Clinically, findings suggest that it is important to encourage pharyngeal constriction while allowing children to find the /r/ tongue shape that best fits their individual vocal tract.

Is statistical learning constrained by lower level perceptual organization?

In order for statistical information to aid in complex developmental processes such as language acquisition, learning from higher-order statistics (e.g. across successive syllables in a speech stream to support segmentation) must be possible while perceptual abilities (e.g. speech categorization) are still developing. The current study examines how perceptual organization interacts with statistical learning. Adult participants were presented with multiple exemplars from novel, complex sound categories designed to reflect some of the spectral complexity and variability of speech. These categories were organized into sequential pairs and presented such that higher-order statistics, defined based on sound categories, could support stream segmentation. Perceptual similarity judgments and multi-dimensional scaling revealed that participants only perceived three perceptual clusters of sounds and thus did not distinguish the four experimenter-defined categories, creating a tension between lower level perceptual organization and higher-order statistical information. We examined whether the resulting pattern of learning is more consistent with statistical learning being "bottom-up," constrained by the lower levels of organization, or "top-down," such that higher-order statistical information of the stimulus stream takes priority over perceptual organization and perhaps influences perceptual organization. We consistently find evidence that learning is constrained by perceptual organization. Moreover, participants generalize their learning to novel sounds that occupy a similar perceptual space, suggesting that statistical learning occurs based on regions of or clusters in perceptual space. Overall, these results reveal a constraint on learning of sound sequences such that statistical information is determined based on lower level organization. These findings have important implications for the role of statistical learning in language acquisition.

The developmental trajectory of children's perception and production of English /r/-/l/

The English /l-r/ distinction is difficult to learn for some second language learners as well as for native-speaking children. This study examines the use of the second (F2) and third (F3) formants in the production and perception of /l/ and /r/ sounds in 4-, 4.5-, 5.5-, and 8.5-yr-old English-speaking children. The children were tested with elicitation and repetition tasks as well as word recognition tasks. The results indicate that whereas young children's /l/ and /r/ in both production and perception show fairly high accuracy and were well defined along the primary acoustic parameter that differentiates them, F3 frequency, these children were still developing in regard to the integration of the secondary cue, F2 frequency. The pattern of development is consistent with the distribution of these features in the ambient input relative to the /l/ and /r/ category distinction: F3 is robust and reliable, whereas F2 is less reliable in distinguishing /l/ and /r/. With delayed development of F2, cue weighting of F3 and F2 for the English /l-r/ categorization seems to continue to develop beyond 8 or 9 yr of age. These data are consistent with a rather long trajectory of phonetic development whereby native categories are refined and tuned well into childhood.

Investigating the use of traditional and spectral biofeedback approaches to intervention for /r/ misarticulation

PURPOSE

Misarticulation of /r/ is among the most challenging developmental speech errors to remediate. Case studies suggest that visual biofeedback treatment can establish perceptually accurate /r/ in clients who have not responded to traditional treatments. This investigation studied the response of children with persistent /r/ misarticulation to a course of traditional treatment and a course of biofeedback treatment.

METHOD

Eleven children with /r/ misarticulation completed 10 weeks of individual treatment consisting of 4-6 weeks of traditional treatment followed by 4-6 weeks of biofeedback treatment. Progress was measured by tracking correct /r/ productions within treatment and probing /r/ in words at 3 time points.

RESULTS

At the group level, there was no difference in independent judges' ratings of /r/ sounds produced by the children before and after traditional treatment. However, /r/ sounds produced after biofeedback treatment were significantly more likely to be rated by the judges as perceptually correct. Eight of the 11 children made measurable gains in the accuracy of isolated /r/ produced within treatment, with 4 showing significant generalization to untreated /r/ in words.

CONCLUSION

This descriptive study shows that treatment incorporating spectral biofeedback can facilitate accurate /r/ production in children with treatment-resistant errors. A follow-up period using traditional intervention methods may be necessary to encourage generalization.

The relationship between inexperienced listeners' perceptions and acoustic correlates of children's /r/ productions

This study examined inexperienced listeners' perceptions of children's naturally produced /r/ sounds with reference to levels of accuracy determined by consensus between two expert clinicians. Participants rated /r/ sounds as fully correct, distorted or incorrect/non-rhotic. Second and third formant heights were measured to explore the relationship between acoustic cues and perceptual judgments. Inexperienced listeners' agreement was greater for correct productions than for distorted or incorrect/non-rhotic productions. In addition, inexperienced listeners' differentiation of intermediate versus fully incorrect /r/ had lower sensitivity and specificity relative to an acoustically defined threshold than experienced listeners' classification. These findings are consistent with results of previous studies highlighting the difficulty in identifying gradations of correctness in misarticulated /r/, and they suggest that this ability may be influenced by clinical experience. Additionally, all listeners were noted to be more consistent in rating vocalic /r/ than consonantal /r/. Implications for clinician training and treatment planning are discussed.

Perception and production of /r/ allophones improve with hearing from a cochlear implant

Tongue shape can vary greatly for allophones of /r/ produced in different phonetic contexts but the primary acoustic cue used by listeners, lowered F3, remains stable. For the current study, it was hypothesized that auditory feedback maintains the speech motor control mechanisms that are constraining acoustic variability of F3 in /r/; thus the listener's percept remains /r/ despite the range of articulatory configurations employed by the speaker. Given the potential importance of auditory feedback, postlingually deafened speakers should show larger acoustic variation in /r/ allophones than hearing controls, and auditory feedback from a cochlear implant could reduce that variation over time. To test these hypotheses, measures were made of phoneme perception and of production of tokens containing /r/, stop consonants, and /r/+stop clusters in hearing controls and in eight postlingually deafened adults pre- and postimplant. Postimplant, seven of the eight implant speakers did not differ from the control mean. It was also found that implant users' production of stop and stop+/r/ blend improved with time but the measured acoustic contrast between these was still better in the control speakers than for the implant group even after the implant users had experienced a year of improved auditory feedback.

Patterns of acquisition of native voice onset time in English-learning children

Learning to speak involves both mastering the requisite articulatory gestures of one's native language and learning to coordinate those gestures according to the rules of the language. Voice onset time (VOT) acquisition illustrates this point: The child must learn to produce the necessary upper vocal tract and laryngeal gestures and to coordinate them with very precise timing. This longitudinal study examined the acquisition of English VOT by audiotaping seven children at 2 month intervals from first words (around 15 months) to the appearance of three-word sentences (around 30 months) in spontaneous speech. Words with initial stops were excerpted, and (1) the numbers of words produced with intended voiced and voiceless initial stops were counted; (2) VOT was measured; and (3) within-child standard deviations of VOT were measured. Results showed that children (1) initially avoided saying words with voiceless initial stops, (2) initially did not delay the onset of the laryngeal adduction relative to the release of closure as long as adults do for voiceless stops, and (3) were more variable in VOT for voiceless than for voiced stops. Overall these results support a model of acquisition that focuses on the mastery of gestural coordination as opposed to the acquisition of segmental contrasts.

Predicting midsagittal pharyngeal dimensions from measures of anterior tongue position in Swedish vowels: statistical considerations

In a re-analysis of x rays of speakers producing Swedish vowels, midsagittal pharyngeal dimensions were predicted from anterior tongue positions using procedures based on estimated tongue pellet positions. Principal component analysis was used to reduce the number of pellet degrees of freedom from eight to three prior to applying linear regression from these three independent variables to dependent vocal tract midsagittal cross distances. Except for the regions around the laryngopharynx and uvula, the pharynx dimensions were predictable from linear regressions and were significant at the p<0.05 level. Numerical experiments show that it is crucial to reduce the number of independent variables in tests of statistical significance.

The use of ultrasound in remediation of North American English /r/ in 2 adolescents

PURPOSE

Ultrasound can provide images of the tongue during speech production. The present study set out to examine the potential utility of ultrasound in remediation of North American English /r/.

METHOD

The participants were 2 Canadian English-speaking adolescents who had not yet acquired /r/. The study included an initial period without ultrasound and 13 treatment sessions, each 1 hr long, using ultrasound. Speech samples were recorded at screening and immediately before and after treatment. Samples were analyzed acoustically and with listener judgments. Ultrasound images were obtained before, during, and after the treatment period.

RESULTS

Three speech-language pathologists unfamiliar with the participants rated significantly more posttreatment tokens as accurate [r]s in single words and some phrases. Acoustic analyses showed an expected lowering of the third formant after treatment. A qualitative observation of posttreatment ultrasound images for accurate [r] tokens showed tongue shapes to be more similar to those of typical adults than had been observed before treatment. Participants needed continued practice of their newly acquired skills in sentences and conversation.

CONCLUSION

Two-dimensional dynamic ultrasound appears to have potential utility for remediation of /r/ in speakers with residual /r/ impairment. Further research is needed with larger numbers of participants to establish the relative efficacy of ultrasound in treatment.

Perception of synthetic vowel exemplars of 4-year-old children and estimation of their corresponding vocal tract shapes

Formant scalings for vowel exemplars of American 4 year olds who were imitating adult production were used along with published data of American adult male vowel production to synthesize /a, ae, u, i/. Other vowel exemplars were also synthesized. Adult listeners were asked to categorize these synthetic vowels in a forced choice task. With some exceptions, the formant frequencies preferred for the vowels /a, ae, u, i/ were close to the published data. In order to gain insight on children's articulation during imitation of vowels /a, ae, u, i/, a five-tube model was used in an algorithm to infer vocal tract shape from the first three formant frequencies of the adult productions, the formant frequencies derived for 4 year olds by scaling, and formant frequencies for 4 year olds derived based on the listening experiments. It was found that the rear tube length for the children, in proportionate terms, was nearly always greater than that of the adult. The rear tube length was proportionately twice as long in children compared to adults for the vowel /u/. Tongue root flexibility and the oblique angle between the pharynx and mouth may be more important than pharynx length in determining formant scalings for 4 year old children.