Using Crowdsourced Listeners' Ratings to Measure Speech Changes in Hypokinetic Dysarthria: A Proof-of-Concept Study

Comparing online versus laboratory measures of speech perception in older children and adolescents

Given the increasing prevalence of online data collection, it is important to know how behavioral data obtained online compare to samples collected in the laboratory. This study compares online and in-person measurement of speech perception in older children and adolescents. Speech perception is important for assessment and treatment planning in speech-language pathology; we focus on the American English /ɹ/ sound because of its frequency as a clinical target. Two speech perception tasks were adapted for web presentation using Gorilla: identification of items along a synthetic continuum from rake to wake, and category goodness judgment of English /ɹ/ sounds in words produced by various talkers with and without speech sound disorder. Fifty typical children aged 9-15 completed these tasks online using a standard headset. These data were compared to a previous sample of 98 typical children aged 9-15 who completed the same tasks in the lab setting. For the identification task, participants exhibited smaller boundary widths (suggestive of more acute perception) in the in-person setting relative to the online setting. For the category goodness judgment task, there was no statistically significant effect of modality. The correlation between scores on the two tasks was significant in the online setting but not in the in-person setting, but the difference in correlation strength was not statistically significant. Overall, our findings agree with previous research in suggesting that online and in-person data collection do not yield identical results, but the two contexts tend to support the same broad conclusions. In addition, these results suggest that online data collection can make it easier for researchers connect with a more representative sample of participants.

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.

Sentence Length Effects on Intelligibility in Two Groups of Older Children With Neurodevelopmental Disorders

PURPOSE

The purpose of this study was to examine the impact of sentence length on intelligibility in two groups of older children with neurodevelopmental disabilities.

METHOD

Nine children diagnosed with cerebral palsy (CP) and eight children diagnosed with Down syndrome (DS), between the ages of 8 and 17 years, repeated sentences varying in length from two to seven words. Three hundred forty adult listeners (20 listeners per child) provided orthographic transcriptions of children's speech, which were used to calculate intelligibility scores.

RESULTS

There was a significant main effect of sentence length on intelligibility for children with CP. Intelligibility significantly increased from two- and three-word sentences to four-, five-, and six-word sentences, then significantly decreased from four-, five-, and six-word sentences to seven-word sentences. There was a main effect of sentence length on intelligibility for children with DS. Intelligibility significantly increased from two-word sentences to four-, five-, and six-word sentences.

CONCLUSIONS

The primary findings of this study include the following: (a) Unlike in typically developing children, sentence length continues to influence intelligibility well into adolescence for children with neurodevelopmental disorders, and (b) sentence length may influence intelligibility differently in children with CP than in children with DS; however, other factors besides the type of neurodevelopmental disorder (e.g., severity of speech motor involvement and/or cognitive-linguistic impairment) could play a role in the relationship between sentence length and intelligibility and must be investigated in future studies.

The Multilevel Word Accuracy Composite Scale: A Novel Measure of Speech Production in Childhood Apraxia of Speech

PURPOSE

The Multilevel word Accuracy Composite Scale (MACS) is a novel whole-word measure of speech production accuracy designed to evaluate behaviors commonly targeted in motor-based intervention for childhood apraxia of speech (CAS). The MACS yields a composite score generated through ratings of segmental accuracy, word structure maintenance, prosody, and movement transition. This study examined the validity of the MACS through comparison to established measures of speech accuracy. Reliability was also examined within and between practicing speech-language pathologists (SLPs).

METHOD

The MACS was used to rate 117 tokens produced by children with severe CAS. Ratings were performed in the laboratory setting by two expert raters and by practicing SLPs (N = 19). Concurrent validity was estimated through comparison of expert MACS ratings (i.e., MACS score and each component rating) to measures of speech accuracy (percent phoneme correct and the 3-point scale) using correlational analyses. Reliability was examined between expert raters and across SLP raters using the intraclass correlation coefficient to examine interrater reliability of expert ratings, in addition to inter- and intrarater reliability of SLP ratings.

RESULTS

Correlation analyses between MACS ratings (i.e., MACS score and component ratings) and existing measures of speech accuracy revealed small to large positive correlations between measures. Reliability analyses revealed moderate to excellent reliability for MACS ratings performed by expert raters and between (interrater) and within (intrarater) SLP raters.

CONCLUSIONS

Analyses of concurrent validity indicate that the MACS aligns with established measures, yet contributes novel elements for rating speech accuracy. Results further support the MACS as a reliable measure for rating speech accuracy in children with severe speech impairment for ratings performed by expert raters and practicing clinicians.

Clinical Assessment of Communication-Related Speech Parameters in Dysarthria: The Impact of Perceptual Adaptation

PURPOSE

In current clinical practice, intelligibility of dysarthric speech is commonly assessed by speech-language therapists (SLTs), in most cases by the therapist caring for the patient being diagnosed. Since SLTs are familiar with dysarthria in general and with the speech of the individual patient to be assessed in particular, they have an adaptation advantage in understanding the patient's utterances. We examined whether and how listeners' assessments of communication-related speech parameters vary as a function of their familiarity with dysarthria in general and with the diagnosed patients in particular.

METHOD

Intelligibility, speech naturalness, and perceived listener effort were assessed in 20 persons with dysarthria (PWD). Patients' speech samples were judged by the individual treating therapists, five dysarthria experts who were unfamiliar with the patients, and crowdsourced naïve listeners. Adaptation effects were analyzed using (a) linear mixed models of overall scoring levels, (b) regression models of severity dependence, (c) network analyses of between-listener and between-parameter relationships, and (d) measures of intra- and interobserver consistency.

RESULTS

Significant advantages of dysarthria experts over laypeople were found in all parameters. An overall advantage of the treating therapists over nonfamiliar experts was only seen in listening effort. Severity-dependent adaptation effects occurred in all parameters. The therapists' responses were heterogeneous and inconsistent with those of the unfamiliar experts and the naïve listeners.

CONCLUSIONS

The way SLTs evaluate communication-relevant speech parameters of the PWD whom they care for is influenced not only by adaptation benefits but also by therapeutic biases. This finding weakens the validity of assessments of communication-relevant speech parameters by the treating therapists themselves and encourages the development and use of alternative methods.

Crowdsourced Perceptual Ratings of Voice Quality in People With Parkinson's Disease Before and After Intensive Voice and Articulation Therapies: Secondary Outcome of a Randomized Controlled Trial

PURPOSE

Limited research has examined the suitability of crowdsourced ratings to measure treatment effects in speakers with Parkinson's disease (PD), particularly for constructs such as voice quality. This study obtained measures of reliability and validity for crowdsourced listeners' ratings of voice quality in speech samples from a published study. We also investigated whether aggregated listener ratings would replicate the original study's findings of treatment effects based on the Acoustic Voice Quality Index (AVQI) measure.

METHOD

This study reports a secondary outcome measure of a randomized controlled trial with speakers with dysarthria associated with PD, including two active comparators (Lee Silverman Voice Treatment [LSVT LOUD] and LSVT ARTIC), an inactive comparator (untreated PD), and a healthy control group. Speech samples from three time points (pretreatment, posttreatment, and 6-month follow-up) were presented in random order for rating as "typical" or "atypical" with respect to voice quality. Untrained listeners were recruited through the Amazon Mechanical Turk crowdsourcing platform until each sample had at least 25 ratings.

RESULTS

Intrarater reliability for tokens presented repeatedly was substantial (Cohen's κ = .65-.70), and interrater agreement significantly exceeded chance level. There was a significant correlation of moderate magnitude between the AVQI and the proportion of listeners classifying a given sample as "typical." Consistent with the original study, we found a significant interaction between group and time point, with the LSVT LOUD group alone showing significantly higher perceptually rated voice quality at posttreatment and follow-up relative to the pretreatment time point.

CONCLUSIONS

These results suggest that crowdsourcing can be a valid means to evaluate clinical speech samples, even for less familiar constructs such as voice quality. The findings also replicate the results of the study by Moya-Galé et al. (2022) and support their functional relevance by demonstrating that the effects of treatment measured acoustically in that study are perceptually apparent to everyday listeners.

A Descriptive Study of Speech Breathing in Children With Cerebral Palsy During Two Types of Connected Speech Tasks

PURPOSE

This study examined speech breathing during two connected speech tasks in children with cerebral palsy (CP) and typically developing (TD) peers. Understanding how the respiratory system supports speech production during various speech tasks can help researchers construct appropriate models of speech production and clinicians remediate speech disorders effectively.

METHOD

Four children with CP and four age- and sex-matched TD peers completed two speech tasks, reading and extemporaneous speech. Respiratory kinematic and acoustic data were collected. Dependent variables included utterance length, speech rate, sound pressure level, and lung volume variables.

RESULTS

Based on descriptive results, children with CP and speech motor involvement demonstrated reduced utterance length and speech rate, equivalent intensity levels, and changes in lung volume variables indicative of respiratory physiological impairment as compared to their TD peers. However, children with CP and no speech motor involvement exhibited speech production and speech breathing variables in the more typical range. In relation to task effects, the majority of children (CP and TD) produced shorter utterances, slower speech rates, equivalent intensity levels, higher lung volume initiation, termination, excursion, higher percent vital capacity per syllable, and longer inspiratory duration during extemporaneous speech as compared to reading.

CONCLUSIONS

Two major themes emerged from the data: (a) Children with CP, particularly those with concomitant speech motor involvement, demonstrate different speech production and speech breathing patterns than their TD peers. (b) Speech task impacts speech production and speech breathing variables in both children with CP and their TD peers, but the extemporaneous speech task did not seem to exaggerate group differences.

Web-based assessment of communication-related parameters in dysarthria: development and implementation of the KommPaS web app

This article describes the design of KommPaS, a web-based tool for the clinical assessment of communication impairment in persons with dysarthria. KommPaS (the German acronym for Communication-related Parameters in Speech Disorders) allows clinicians to recruit laypersons via crowdsourcing for the evaluation of samples of dysarthric speech with regard to communication relevant parameters, that is, intelligibility, naturalness, perceived listener effort, and efficiency (intelligible speech units per unit time). Moreover, a communication total score describing the KommPaS profile elevation, i.e., the arithmetic mean of the normalized KommPaS scores, is provided. Based on considerations regarding the theoretical underpinnings and methodological constraints of a clinical tool for the assessment of these parameters, the article describes how each theoretically and methodologically motivated feature is translated into design principles and how these principles are implemented in a web application. The paper reports efficiency data and details the data privacy and data security provisions that are essential in such an approach.

Clinical measures of communication limitations in dysarthria assessed through crowdsourcing: specificity, sensitivity, and retest-reliability

Assessing the impact of dysarthria on a patient's ability to communicate should be an integral part of patient management. However, due to the high demands on reliable quantification of communication limitations, hardly any formal clinical tests with approved psychometric properties have been developed so far. This study investigates a web-based assessment of communication impairment in dysarthria, named KommPaS. The test comprises measures of intelligibility, naturalness, perceived listener effort and communication efficiency, as well as a total score that integrates these parameters. The approach is characterized by a quasi-random access to a large inventory of test materials and to a large group of naïve listeners, recruited via crowdsourcing. As part of a larger research program to establish the clinical applicability of this new approach, the present paper focuses on two psychometric issues, namely specificity and sensitivity (study 1) and retest-reliability (study 2). Study 1: KommPaS was administered to 54 healthy adults and 100 adult persons with dysarthria (PWD). Non-parametric criterion-based norms (specificity: 0.95) were used to derive a standard metric for each of the four component variables, and corresponding sensitivity values for the presence of dysarthria were identified. Overall classification accuracy of the total score was determined using a ROC analysis. The resulting cutscores showed a high accuracy in the separation of PWD from healthy speakers for the naturalness and the total score. Study 2: A sub-group of 20 PWD enrolled in study 1 were administered a second KommPaS examination. ICC analyses revealed good to excellent retest reliabilities for all parameters.

Baseline Stimulability Predicts Patterns of Response to Traditional and Ultrasound Biofeedback Treatment for Residual Speech Sound Disorder

PURPOSE

This study aimed to identify predictors of response to treatment for residual speech sound disorder (RSSD) affecting English rhotics. Progress was tracked during an initial phase of traditional motor-based treatment and a longer phase of treatment incorporating ultrasound biofeedback. Based on previous literature, we focused on baseline stimulability and sensory acuity as predictors of interest.

METHOD

Thirty-three individuals aged 9-15 years with residual distortions of /ɹ/ received a course of individual intervention comprising 1 week of intensive traditional treatment and 9 weeks of ultrasound biofeedback treatment. Stimulability for /ɹ/ was probed prior to treatment, after the traditional treatment phase, and after the end of all treatment. Accuracy of /ɹ/ production in each probe was assessed with an acoustic measure: normalized third formant (F3)-second formant (F2) distance. Model-based clustering analysis was applied to these acoustic measures to identify different average trajectories of progress over the course of treatment. The resulting clusters were compared with respect to acuity in auditory and somatosensory domains.

RESULTS

All but four individuals were judged to exhibit a clinically significant response to the combined course of treatment. Two major clusters were identified. The "low stimulability" cluster was characterized by very low accuracy at baseline, minimal response to traditional treatment, and strong response to ultrasound biofeedback. The "high stimulability" group was more accurate at baseline and made significant gains in both traditional and ultrasound biofeedback phases of treatment. The clusters did not differ with respect to sensory acuity.

CONCLUSIONS

This research accords with clinical intuition in finding that individuals who are more stimulable at baseline are more likely to respond to traditional intervention, whereas less stimulable individuals may derive greater relative benefit from biofeedback.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20422236.

Telepractice Treatment of Residual Rhotic Errors Using App-Based Biofeedback: A Pilot Study

PURPOSE

Although mobile apps are used extensively by speech-language pathologists, evidence for app-based treatments remains limited in quantity and quality. This study investigated the efficacy of app-based visual-acoustic biofeedback relative to nonbiofeedback treatment using a single-case randomization design. Because of COVID-19, all intervention was delivered via telepractice.

METHOD

Participants were four children aged 9-10 years with residual errors affecting American English /ɹ/. Using a randomization design, individual sessions were randomly assigned to feature practice with or without biofeedback, all delivered using the speech app Speech Therapist's App for /r/ Treatment. Progress was assessed using blinded listener ratings of word probes administered at baseline, posttreatment, and immediately before and after each treatment session.

RESULTS

All participants showed a clinically significant response to the overall treatment package, with effect sizes ranging from moderate to very large. One participant showed a significant advantage for biofeedback over nonbiofeedback treatment, although the order of treatment delivery poses a potential confound for interpretation in this case.

CONCLUSIONS

While larger scale studies are needed, these results suggest that app-based treatment for residual errors can be effective when delivered via telepractice. These results are compatible with previous findings in the motor learning literature regarding the importance of treatment dose and the timing of feedback conditions.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.18461576.

Intelligibility Across a Reading Passage: The Effect of Dysarthria and Cued Speaking Styles

OBJECTIVE

Reading a passage out loud is a commonly used task in the perceptual assessment of dysarthria. The extent to which perceptual characteristics remain unchanged or stable over the time course of a passage is largely unknown. This study investigated crowdsourced visual analogue scale (VAS) judgments of intelligibility across a reading passage as a function of cued speaking styles commonly used in treatment to maximize intelligibility.

PATIENTS AND METHOD

The Hunter passage was read aloud in habitual, slow, loud, and clear speaking styles by 16 speakers with Parkinson's disease (PD), 30 speakers with multiple sclerosis (MS), and 32 control speakers. VAS judgments of intelligibility from three fragments representing the beginning, middle, and end of the reading passage were obtained from 540 crowdsourced online listeners.

RESULTS

Overall passage intelligibility was reduced for the two clinical groups relative to the control group. All speaker groups exhibited intelligibility variation across the reading passage, with trends of increased intelligibility toward the end of the reading passage. For control speakers and speakers with PD, patterns of intelligibility variation across passage reading did not differ with speaking style. For the MS group, intelligibility variation across the passage was dependent on speaking style.

CONCLUSIONS

The presence of intelligibility variation within a reading passage warrants careful selection of speech materials in research and clinical practice. Results further indicate that the crowdsourced VAS rating paradigm is useful to document intelligibility in a reading passage for different cued speaking styles commonly used in treatment for dysarthria.

Indicators of Communication Limitation in Dysarthria and Their Relation to Auditory-Perceptual Speech Symptoms: Construct Validity of the KommPaS Web App

PURPOSE

Despite extensive research into communication-related parameters in dysarthria, such as intelligibility, naturalness, and perceived listener effort, the existing evidence has not been translated into a clinically applicable, comprehensive, and valid diagnostic tool so far. This study addresses Communication-Related Parameters in Speech Disorders (KommPaS), a new web-based diagnostic instrument for measuring indices of communication limitation in individuals with dysarthria through online crowdsourcing. More specifically, it answers questions about the construct validity of KommPaS. In the first part, the interrelationship of the KommPaS variables intelligibility, naturalness, perceived listener effort, and speech rate were explored in order to draw a comprehensive picture of a patient's limitations and avoid the collection of redundant information. Second, the influences of motor speech symptoms on the KommPaS variables were studied in order to delineate the structural relationships between two complementary diagnostic perspectives.

METHOD

One hundred persons with dysarthria of different etiologies and varying degrees of severity were examined with KommPaS to obtain layperson-based data on communication-level parameters, and with the Bogenhausen Dysarthria Scale (BoDyS) to obtain expert-based, function-level data on dysarthria symptoms. The internal structure of the KommPaS variables and their dependence on the BoDyS variables were analyzed using structural equation modeling.

RESULTS

Despite a high multicollinearity, all KommPaS variables were shown to provide complementary diagnostic information and their mutual interconnections were delineated in a path graph model. Regarding the influence of the BoDyS scales on the KommPaS variables, separate linear regression models revealed plausible predictor sets. A complete path model of KommPaS and BoDyS variables was developed to map the complex interplay between variables at the functional and the communication levels of dysarthria assessment.

CONCLUSION

In validating a new clinical tool for the diagnostics of communication limitations in dysarthria, this study is the first to draw a comprehensive picture of how auditory-perceptual characteristics of dysarthria interact at the levels of expert-based functional and layperson-based communicative assessments.

Crowdsourcing as a tool in the clinical assessment of intelligibility in dysarthria: How to deal with excessive variation

PURPOSE

Independent laypersons are essential in the assessment of intelligibility in persons with dysarthria (PWD), as they reflect intelligibility limitations in the most ecologically valid way, without being influenced by familiarity with the speaker. The present work investigated online crowdsourcing as a convenient method to involve lay people as listeners, with the objective of exploring how to constrain the expected variability of crowd-based judgements to make them applicable in clinical diagnostics.

METHOD

Intelligibility was assessed using a word transcription task administered via crowdsourcing. In study 1, speech samples of 23 PWD were transcribed by 18 crowdworkers each. Four methods of aggregating the intelligibility scores of randomly sampled panels of 4 to 14 listeners were compared for accuracy, i.e. the stability of the resulting intelligibility estimates across different panels, and their validity, i.e. the degree to which they matched data obtained under controlled laboratory conditions ("gold standard"). In addition, we determined an economically acceptable number of crowdworkers per speaker which is needed to obtain accurate and valid intelligibility estimates. Study 2 examined the robustness of the chosen aggregation method against downward outliers due to spamming in a larger sample of 100 PWD.

RESULTS

In study 1, an interworker aggregation method based on negative exponential weightings of the scores as a function of their distance from the "best" listener's score (exponentially weighted mean) outperformed three other methods (median value, arithmetic mean, maximum). Under cost-benefit considerations, an optimum panel size of 9 crowd listeners per examination was determined. Study 2 demonstrated the robustness of this aggregation method against spamming crowd listeners.

CONCLUSION

Though intelligibility data collected through online crowdsourcing are noisy, accurate and valid intelligibility estimates can be obtained by appropriate aggregation of the raw data. This makes crowdsourcing a suitable method for incorporating real-world perspectives into clinical dysarthria assessment.

Single Word Intelligibility of Individuals with Parkinson's Disease in Noise: Pre-Specified Secondary Outcome Variables from a Randomized Control Trial (RCT) Comparing Two Intensive Speech Treatments (LSVT LOUD vs. LSVT ARTIC)

The majority of people with Parkinson's disease (PD) experience both prosodic changes (reduced vocal volume, reduced pitch range) and articulatory changes (imprecise articulation) that often limit speech intelligibility and may contribute to significant declines in quality of life. We conducted a randomized control trial comparing two intensive treatments, voice (LSVT LOUD) or articulation (LSVT ARTIC) to assess single word intelligibility in the presence of background noise (babble and mall). Participants (64 PD and 20 Healthy) read words from the diagnostic rhyme test (DRT), an ANSI Standard for measuring intelligibility of speech, before and after one month (treatment or no treatment). Teams of trained listeners blindly rated the data. Speech intelligibility of words in the presence of both noise conditions improved in PD participants who had LSVT LOUD compared to the groups that had LSVT ARTIC or no treatment. Intensive speech treatment targeting prominent prosodic variables in LSVT LOUD had a positive effect on speech intelligibility at the single word level in PD.

Investigating Acoustic Correlates of Intelligibility Gains and Losses During Slowed Speech: A Hybridization Approach

Purpose This exploratory study sought to identify acoustic variables explaining rate-related variation in intelligibility for speakers with dysarthria secondary to multiple sclerosis. Method Seven speakers with dysarthria due to multiple sclerosis produced the same set of Harvard sentences at habitual and slow rates. Speakers were selected from a larger corpus on the basis of rate-related intelligibility characteristics. Four speakers demonstrated improved intelligibility and three speakers demonstrated reduced intelligibility when rate was slowed. A speech analysis resynthesis paradigm termed hybridization was used to create stimuli in which segmental (i.e., short-term spectral) and suprasegmental variables (i.e., sentence-level fundamental frequency, energy characteristics, and duration) of sentences produced at the slow rate were donated individually or in combination to habitually produced sentences. Online crowdsourced orthographic transcription was used to quantify intelligibility for six hybridized sentence types and the original habitual and slow productions. Results Sentence duration alone was not a contributing factor to improved intelligibility associated with slowed rate. Speakers whose intelligibility improved with slowed rate showed higher intelligibility scores for duration spectrum hybrids and energy hybrids compared to the original habitual rate sentences, suggesting these acoustic cues contributed to improved intelligibility for sentences produced with a slowed rate. Energy contour characteristics were also found to play a role in intelligibility losses for speakers with decreased intelligibility at slowed rate. The relative contribution of speech acoustic variables to intelligibility gains and losses varied considerably between speakers. Conclusions Hybridization can be used to identify acoustic correlates of intelligibility variation associated with slowed rate. This approach has further elucidated speaker-specific and individualized speech production adjustments when slowing rate.

The Impact of Lexical and Articulatory Factors in the Automatic Selection of Test Materials for a Web-Based Assessment of Intelligibility in Dysarthria

Purpose The clinical assessment of intelligibility must be based on a large repository and extensive variation of test materials, to render test stimuli unpredictable and thereby avoid expectancies and familiarity effects in the listeners. At the same time, it is essential that test materials are systematically controlled for factors influencing intelligibility. This study investigated the impact of lexical and articulatory characteristics of quasirandomly selected target words on intelligibility in a large sample of dysarthric speakers under clinical examination conditions. Method Using the clinical assessment tool KommPaS, a total of 2,700 sentence-embedded target words, quasirandomly drawn from a large corpus, were spoken by a group of 100 dysarthric patients and later transcribed by listeners recruited via online crowdsourcing. Transcription accuracy was analyzed for influences of lexical frequency, phonological neighborhood structure, articulatory complexity, lexical familiarity, word class, stimulus length, and embedding position. Classification and regression analyses were performed using random forests and generalized linear mixed models. Results Across all degrees of severity, target words with higher frequency, fewer and less frequent phonological neighbors, higher articulatory complexity, and higher lexical familiarity received significantly higher intelligibility scores. In addition, target words were more challenging sentence-initially than in medial or final position. Stimulus length had mixed effects; word length and word class had no effect. Conclusions In a large-scale clinical examination of intelligibility in speakers with dysarthria, several well-established influences of lexical and articulatory parameters could be replicated, and the roles of new factors were discussed. This study provides clues about how experimental rigor can be combined with clinical requirements in the diagnostics of communication impairment in patients with dysarthria.

Acoustic vowel analysis and speech intelligibility in young adult Hebrew speakers: Developmental dysarthria versus typical development

BACKGROUND

Developmental dysarthria is a motor speech impairment commonly characterized by varying levels of reduced speech intelligibility. The relationship between intelligibility deficits and acoustic vowel space among these individuals has long been noted in the literature, with evidence of vowel centralization (e.g., in English and Mandarin). However, the degree to which this centralization occurs and the intelligibility-acoustic relationship is maintained in different vowel systems has yet to be studied thoroughly. In comparison with American English, the Hebrew vowel system is significantly smaller, with a potentially smaller vowel space area, a factor that may impact upon the comparisons of the acoustic vowel space and its correlation with speech intelligibility. Data on vowel space and speech intelligibility are particularly limited for Hebrew speakers with motor speech disorders.

AIMS

To determine the nature and degree of vowel space centralization in Hebrew-speaking adolescents and young adults with dysarthria, in comparison with typically developing (TD) peers, and to correlate these findings with speech intelligibility scores.

METHODS & PROCEDURES

Adolescents and young adults with developmental dysarthria (secondary to cerebral palsy (CP) and other motor deficits, n = 17) and their TD peers (n = 17) were recorded producing Hebrew corner vowels within single words. For intelligibility assessments, naïve listeners transcribed those words produced by speakers with CP, and intelligibility scores were calculated.

OUTCOMES & RESULTS

Acoustic analysis of vowel formants (F1, F2) revealed a centralization of vowel space among speakers with CP for all acoustic metrics of vowel formants, and mainly for the formant centralization ratio (FCR), in comparison with TD peers. Intelligibility scores were correlated strongly with the FCR metric for speakers with CP.

CONCLUSIONS & IMPLICATIONS

The main results, vowel space centralization for speakers with CP in comparison with TD peers, echo previous cross-linguistic results. The correlation of acoustic results with speech intelligibility carries clinical implications. Taken together, the results contribute to better characterization of the speech production deficit in Hebrew speakers with motor speech disorders. Furthermore, they may guide clinical decision-making and intervention planning to improve speech intelligibility. What this paper adds What is already known on the subject Speech production and intelligibility deficits among individuals with developmental dysarthria (e.g., secondary to CP) are well documented. These deficits have also been correlated with centralization of the acoustic vowel space, although primarily in English speakers. Little is known about the acoustic characteristics of vowels in Hebrew speakers with motor speech disorders, and whether correlations with speech intelligibility are maintained. What this paper adds to existing knowledge This study is the first to describe the acoustic characteristics of vowel space in Hebrew-speaking adolescents and young adults with developmental dysarthria. The results demonstrate a centralization of the acoustic vowel space in comparison with TD peers for all measures, as found in other languages. Correlation between acoustic measures and speech intelligibility scores were also documented. We discuss these results within the context of cross-linguistic comparisons. What are the potential or actual clinical implications of this work? The results confirm the use of objective acoustic measures in the assessment of individuals with motor speech disorders, providing such data for Hebrew-speaking adolescents and young adults. These measures can be used to determine the nature and severity of the speech deficit across languages, may guide intervention planning, as well as measure the effectiveness of intelligibility-based treatment programmes.