Effect of Dysarthria Type, Speaking Condition, and Listener Age on Speech Intelligibility

Effects of speech rate modifications on phonatory acoustic outcomes in Parkinson's disease

Speech rate reduction is a global speech therapy approach for speech deficits in Parkinson's disease (PD) that has the potential to result in changes across multiple speech subsystems. While the overall goal of rate reduction is usually improvements in speech intelligibility, not all people with PD benefit from this approach. Speech rate is often targeted as a means of improving articulatory precision, though less is known about rate-induced changes in other speech subsystems that could help or hinder communication. The purpose of this study was to quantify phonatory changes associated with speech rate modification across a broad range of speech rates from very slow to very fast in talkers with and without PD. Four speaker groups participated: younger and older healthy controls, and people with PD with and without deep brain stimulation of the subthalamic nucleus (STN-DBS). Talkers read aloud standardized sentences at 7 speech rates elicited using magnitude production: habitual, three slower rates, and three faster rates. Acoustic measures of speech intensity, cepstral peak prominence, and fundamental frequency were measured as a function of speech rate and group. Overall, slower rates of speech were associated with differential effects on phonation across the four groups. While all talkers spoke at a lower pitch in slow speech, younger talkers showed increases in speech intensity and cepstral peak prominence, while talkers with PD and STN-DBS showed the reverse pattern. Talkers with PD without STN-DBS and older healthy controls behaved in between these two extremes. At faster rates, all groups uniformly demonstrated increases in cepstral peak prominence. While speech rate reductions are intended to promote positive changes in articulation to compensate for speech deficits in dysarthria, the present results highlight that undesirable changes may be invoked across other subsystems, such as at the laryngeal level. In particular, talkers with STN-DBS, who often demonstrate speech deterioration following DBS surgery, demonstrated more phonatory detriments at slowed speech rates. Findings have implications for speech rate candidacy considerations and speech motor control processes in PD.

A Matter of Time: A Web-Based Investigation of Rest and Sleep Effects on Speech Motor Learning

PURPOSE

Here, we examine the possibility that memory consolidation during a period of postpractice rest or nocturnal sleep can bolster speech motor learning in the absence of additional practice or effort.

METHOD

Using web-administered experiments, 74 typical, American English talkers trained in a nonnative vowel contrast then had a 12-hr delay with (SLEEP) or without nocturnal sleep (REST) or proceeded immediately (IMMEDIATE) to a posttraining production assessment. For ecological validity, 51 native Danish talkers perceptually identified the American English talkers' productions.

RESULTS

We observed that practice resulted in productions that were more acoustically similar to the Danish target. In addition, we found that rest in the absence of further practice reduced the token-to-token variability of the productions. Last, for vowels produced immediately following training, listeners more accurately identified vowels in the trained context, whereas in the untrained context, listener accuracy improved only for vowels produced by talkers who slept.

CONCLUSIONS

A single session of speech motor training promotes observable change to speech production behavior. Specifically, practice facilitates acoustic similarity to the target. Moreover, although a 12-hr postpractice period of rest appears to promote productions that are less variable, only the productions of those who slept are perceived as more accurate by listeners. This may point to sleep's role in contextualizing the acoustic goal of the production to the learner's own vocal tract and its role as a protective mechanism during learning. These results are unaccounted for under existing models and offer potential for future educational and clinical applications to maximize speech motor learning.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.24707442.

The Influence of Sensorineural Hearing Loss on the Relationship Between the Perception of Speech in Noise and Dysarthric Speech

PURPOSE

The ability to understand speech under adverse listening conditions is highly variable across listeners. Despite this, studies have found that listeners with normal hearing display consistency in their ability to perceive speech across different types of degraded speech, suggesting that, for at least these listeners, global skills may be involved in navigating the ambiguity in speech signals. However, there are substantial differences in the perceptual challenges faced by listeners with normal and impaired hearing. This study examines whether listeners with sensorineural hearing loss demonstrate the same type of consistency as normal-hearing listeners when processing neurotypical (i.e., control) speech that has been degraded by external noise and speech that is neurologically degraded such as dysarthria.

METHOD

Listeners with normal hearing (n = 31) and listeners with sensorineural hearing loss (n = 36) completed an intelligibility task with neurotypical speech in noise and with dysarthric speech in quiet.

RESULTS

Findings were consistent with previous work demonstrating a relationship between the ability to perceive neurotypical speech in noise and dysarthric speech for listeners with normal hearing, albeit at a higher intelligibility level than previously observed. This relationship was also observed for listeners with hearing loss, although listeners with more severe hearing losses performed better with dysarthric speech than with neurotypical speech in noise.

CONCLUSIONS

This study demonstrated a high level of consistency in intelligibility performance for listeners across two different types of degraded speech, even when those listeners were further challenged by the presence of sensorineural hearing loss. Clinical implications for both listeners with hearing loss and their communication partners with dysarthria are discussed.

Acoustic Predictors of Ease of Understanding in Spanish Speakers With Dysarthria Associated With Parkinson's Disease

PURPOSE

The purpose of this study was to examine selected baseline acoustic features of hypokinetic dysarthria in Spanish speakers with Parkinson's disease (PD) and identify potential acoustic predictors of ease of understanding in Spanish.

METHOD

Seventeen Spanish-speaking individuals with mild-to-moderate hypokinetic dysarthria secondary to PD and eight healthy controls were recorded reading a translation of the Rainbow Passage. Acoustic measures of vowel space area, as indicated by the formant centralization ratio (FCR), envelope modulation spectra (EMS), and articulation rate were derived from the speech samples. Additionally, 15 healthy adults rated ease of understanding of the recordings on a visual analogue scale. A multiple linear regression model was implemented to investigate the predictive value of the selected acoustic parameters on ease of understanding.

RESULTS

Listeners' ease of understanding was significantly lower for speakers with dysarthria than for healthy controls. The FCR, EMS from the first 10 s of the reading passage, and the difference in EMS between the end and the beginning sections of the passage differed significantly between the two groups of speakers. Findings indicated that 67.7% of the variability in ease of understanding was explained by the predictive model, suggesting a moderately strong relationship between the acoustic and perceptual domains.

CONCLUSIONS

Measures of envelope modulation spectra were found to be highly significant model predictors of ease of understanding of Spanish-speaking individuals with hypokinetic dysarthria associated with PD. Articulation rate was also found to be important (albeit to a lesser degree) in the predictive model. The formant centralization ratio should be further examined with a larger sample size and more severe dysarthria to determine its efficacy in predicting ease of understanding.

The Application of Time-Frequency Masking To Improve Intelligibility of Dysarthric Speech in Background Noise

PURPOSE

Background noise reduces speech intelligibility. Time-frequency (T-F) masking is an established signal processing technique that improves intelligibility of neurotypical speech in background noise. Here, we investigated a novel application of T-F masking, assessing its potential to improve intelligibility of neurologically degraded speech in background noise.

METHOD

Listener participants (N = 422) completed an intelligibility task either in the laboratory or online, listening to and transcribing audio recordings of neurotypical (control) and neurologically degraded (dysarthria) speech under three different processing types: speech in quiet (quiet), speech mixed with cafeteria noise (noise), and speech mixed with cafeteria noise and then subsequently processed by an ideal quantized mask (IQM) to remove the noise.

RESULTS

We observed significant reductions in intelligibility of dysarthric speech, even at highly favorable signal-to-noise ratios (+11 to +23 dB) that did not impact neurotypical speech. We also observed significant intelligibility improvements from speech in noise to IQM-processed speech for both control and dysarthric speech across a wide range of noise levels. Furthermore, the overall benefit of IQM processing for dysarthric speech was comparable with that of the control speech in background noise, as was the intelligibility data collected in the laboratory versus online.

CONCLUSIONS

This study demonstrates proof of concept, validating the application of T-F masks to a neurologically degraded speech signal. Given that intelligibility challenges greatly impact communication, and thus the lives of people with dysarthria and their communication partners, the development of clinical tools to enhance intelligibility in this clinical population is critical.

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.

Intelligibility, Speech Rate, and Communication Efficiency in Children With Neurological Conditions: A Longitudinal Study of Childhood Dysarthria

PURPOSE

This study aimed to describe communication-related parameters (i.e., intelligibility, speech rate, and communication efficiency) and their developmental courses in children with neurological conditions against the background of typical development. In addition, interrelations between the developmental courses of communication-related parameters and auditory-perceptual ratings related to speech subsystems were investigated.

METHOD

Fourteen children with neurological conditions (CNC) and 14 typically developing children (CTD), matched for age and gender (four girls; 5;1-8;4 [years;months] at first examination), were assessed at three points in time over an 18-month period. Speech samples were collected using the Bogenhausener Dysarthrie Skalen-Kindliche Dysarthrien (English: Bogenhausen Dysarthria Scales-Childhood Dysarthria), a German tool for the assessment of childhood dysarthria. To assess intelligibility, naïve listeners transcribed audio samples of sentence repetitions of the children. Speech rate was measured by acoustic analyses, and communication efficiency was determined by multiplying the proportion of correctly transcribed syllables with speech rate. Age normalization was performed following a recently published approach.

RESULTS

On the group level, CNC had conspicuous raw and normalized scores for the three communication-related parameters and were more variable than the CTD group regarding their developmental courses. These differences were more pronounced for intelligibility than for speech rate. A strong relationship between communication-related and speech subsystems-related auditory-perceptual characteristics was apparent only between intelligibility and articulation/resonance.

CONCLUSIONS

For the first time, age-normalized scores for communication-related parameters were reported in children with neurological disorders and put into a developmental context within the framework of a longitudinal study. Age-normalized intelligibility was more vulnerable to large developmental changes than speech rate and was best predicted by changes in articulation and resonance. Overall, this study may contribute to a more comprehensive and valid clinical assessment of childhood dysarthria and to a better understanding of its developmental dynamics.

The Effects of Intensive Voice Treatment in Mandarin Speakers With Parkinson's Disease: Acoustic and Perceptual Findings

PURPOSE

This study investigated the effects of intensive voice treatment on subjective and objective measures of speech production in Mandarin speakers with hypokinetic dysarthria.

METHOD

Nine Mandarin speakers with hypokinetic dysarthria due to Parkinson's disease received 4 weeks of intensive voice treatment (4 × 60 min per week). The speakers were recorded reading a passage before treatment (PRE), immediately after treatment (POST), and at 6-month follow-up (FU). Listeners (n = 15) rated relative ease of understanding (EOU) of paired speech samples on a visual analogue scale. Acoustic analyses were performed. Changes in EOU, vocal intensity, global and local fundamental frequency (f _o) variation, speech rate, and acoustic vowel space area (VSA) were examined.

RESULTS

Increases were found in EOU and vocal intensity from PRE to POST and from PRE to FU, with no change found from POST to FU. Speech rate increased from PRE to POST, with limited evidence of an increase from PRE to FU and no change from POST to FU. No changes in global or local f _o variation or in VSA were found.

CONCLUSIONS

Intensive voice treatment shows promise for improving speech production in Mandarin speakers with hypokinetic dysarthria. Vocal intensity, speech rate, and, crucially, intelligibility, may improve for up to 6 months posttreatment. In contrast, f _o variation and VSA may not increase following the treatment.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.19529017.

From Speech Acoustics to Communicative Participation in Dysarthria: Toward a Causal Framework

PURPOSE

We proposed and tested a causal instantiation of the World Health Organization's International Classification of Functioning, Disability and Health (ICF) framework, linking acoustics, intelligibility, and communicative participation in the context of dysarthria.

METHOD

Speech samples and communicative participation scores were collected from individuals with dysarthria (n = 32). Speech was analyzed for two acoustic metrics (i.e., articulatory precision and speech rate), and an objective measure of intelligibility was generated from listener transcripts. Mediation analysis was used to evaluate pathways of effect between acoustics, intelligibility, and communicative participation.

RESULTS

We observed a strong relationship between articulatory precision and intelligibility and a moderate relationship between intelligibility and communicative participation. Collectively, data supported a significant relationship between articulatory precision and communicative participation, which was almost entirely mediated through intelligibility. These relationships were not significant when speech rate was specified as the acoustic variable of interest.

CONCLUSION

The statistical corroboration of our causal instantiation of the ICF framework with articulatory acoustics affords important support toward the development of a comprehensive causal framework to understand and, ultimately, address restricted communicative participation in 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.

Intelligibility, Articulation Rate, Fluency, and Communicative Efficiency in Typically Developing Children

Purpose This article describes the developmental trajectories of four communication-related parameters (i.e., intelligibility, articulation rate, fluency, and communicative efficiency) in a cross-sectional study of typically developing children between 3 and 9 years. The four target parameters were related to auditory-perceptual parameters of speech function. Method One hundred forty-four typically developing children (ages 3;0-9;11 [years;months]; 72 girls and 72 boys) participated. Speech samples were collected using the materials of the Bogenhausen Dysarthria Scales for Childhood Dysarthria, a German assessment tool for childhood dysarthria, and analyzed following established auditory-perceptual criteria on relevant speech functions. To assess intelligibility, naïve listeners transcribed sentences repeated by the children. Articulation rate and fluency were measured by acoustic analyses; communicative efficiency was determined by multiplying the proportion of correctly transcribed syllables by speech rate. Results Intelligibility showed a steep developmental trajectory, with the majority of children obtaining a proportion of intelligible syllables close to 1.0 at the age of 5 years. Articulation rate demonstrated a flatter trajectory, with high variability still within the older children. Disfluencies, on the contrary, occurred only in the youngest children. By definition, communicative efficiency shared the characteristics of intelligibility and rate curves. A principal component analysis revealed, among other findings, strong connections between intelligibility and articulation, as well as between communicative efficiency, articulation, and rate measures. Conclusions While children speak intelligibly, in terms of the applied assessment, at a comparably young age, other communication-relevant parameters show a slower developmental progress. Knowledge on the typical development of communication-related parameters and on their complex relationships with functional speech variables is crucial for the clinical assessment of childhood dysarthria. Supplemental Material https://doi.org/10.23641/asha.14880285.

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.

Stability of Speech Intelligibility Measures Over Repeated Sampling Times in Speakers With Acquired Apraxia of Speech

Purpose The purpose of this investigation was to measure the test-retest stability of single-word intelligibility in a group of 28 speakers with chronic apraxia of speech and aphasia. Method The Assessment of Intelligibility of Dysarthric Speech was administered twice to each participant, with samples separated by 1 week. Scoring of recorded samples was completed independently by three expert listeners using transcription and multiple-choice scoring formats. Results Percent intelligible words was very similar for the group over the two sampling times for both scoring formats (i.e., within 1.5%), with no statistically significant differences found between times. Statistically significant, very strong, positive correlations were found between sampling times for intelligibility scores. Transcription and multiple-choice scores were strongly, positively correlated, with multiple-choice scores being statistically higher. There was a statistically significant difference between mean transcription and multiple-choice scores for the group at Time 1 and Time 2. Individual performance was similar to group performance for the majority of participants. Conclusions These findings indicate that single-word intelligibility measures are stable over repeated sampling occasions. Stability was evident for transcription and multiple-choice scoring methods. Supplemental Material https://doi.org/10.23641/asha.14226737.

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.

Variation in Speech Intelligibility Ratings as a Function of Speech Rate Modification in Parkinson's Disease

Purpose The aim of this study was to quantify changes in speech intelligibility in two cohorts of people with Parkinson's disease (PD; those with and without deep brain stimulation [DBS]) across a broad range of self-selected speech rate alterations in (a) read sentences and (b) extemporaneous speech (monologues). Method Four speaker groups participated in this study: younger and older controls, people with PD undergoing standard pharmaceutical treatment, and people with PD and DBS. Naïve listeners rated the intelligibility of read sentences and extemporaneous monologues, spoken by participants at seven self-selected speech rates from very slow to very fast. Intelligibility was modeled as a function of group, speech rate condition, and speech task. Results Overall, compared to habitual speech rate, slower speech rate conditions were not associated with changes in speech intelligibility, whereas faster-than-habitual conditions were associated in declines in intelligibility. Results were mediated by group and task effects, such that talkers with PD and DBS were more likely to see intelligibility benefits at slower self-selected speech rates and less likely to see detriments at faster rates, and these differences were amplified in monologues compared to sentences. Conclusion Findings suggest differences in the ways in which slower and faster speech rate adjustments impact speech intelligibility in people with PD with and without DBS, with the latter demonstrating greater magnitudes of change.

Neuromotor Speech Recovery Across Different Behavioral Speech Modifications in Individuals Following Facial Transplantation

Despite signs of facial nerve recovery within a few months following face transplantation, speech deficits persist for years. Behavioral speech modifications (e.g., slower-than-normal speaking rate and increased loudness) have shown promising potential to enhance speech intelligibility in populations with dysarthric speech. However, such evidence-based practice approach is lacking in clinical management of speech in individuals with facial transplantation. Because facial transplantation involves complex craniofacial reconstruction and facial nerve coaptation, it is unknown to what extent individuals with face transplant are capable of adapting their motor system to task-specific articulatory demands. The purpose of this study was to identify the underlying articulatory mechanisms employed by individuals with face transplantation in response to speech modification cues at early and late stages of neuromotor recovery. In addition, we aimed to identify speech modifications that conferred improved speech clarity. Participants were seven individuals who underwent full or partial facial vascularized composite allografts that included lips and muscles of facial animation and were in early (~2 months) or late (~42 months) stages of recovery. Participants produced repetitions of the sentence “Buy Bobby a puppy” in normal, fast, loud, and slow speech modifications. Articulatory movement traces were recorded using a 3D optical motion capture system. Kinematic measures of average speed (mm/s) and range of movement (mm³) were extracted from the lower lip (± jaw) marker. Two speech language pathologists rated speech clarity for each speaker using a visual analog scale (VAS) approach. Results demonstrated that facial motor capacity increased from early to late stages of recovery. While individuals in the early group exhibited restricted capabilities to adjust their motor system based on the articulatory demands of each speech modification, individuals in the late group demonstrated faster speed and larger-than-normal range of movement for loud speech, and slower speed and larger-than-normal range of movement for slow speech. In addition, subjects in both groups showed overreliance on jaw rather than lip articulatory function across all speech modifications, perhaps as a compensatory strategy to optimize articulatory stability and maximize speech function. Finally, improved speech clarity was associated with loud speech in both stages of recovery.

Investigation of Different Time-Frequency Representations for Intelligibility Assessment of Dysarthric Speech

Speech disorders linked to neurological problems affect person's ability to communicate through speech. Dysarthria is one of the speech disorders caused due to muscle weakness producing slow, slurred and less intelligible speech. Automatic intelligibility assessment of dysarthria from speech can be used as a promising clinical tool in treatment. This paper explores the use of perceptually enhanced Fourier transform spectrograms and Constant-Q transform spectrograms with CNN to assess word level and sentence level intelligibility of dysarthric speech from UA and TORGO databases. Constant-Q transform and perceptually enhanced mel warped STFT spectrograms performed better in the classification task.

A Comparison of Speech Amplification and Personal Communication Devices for Hypophonia

Purpose This study compared the performance of three amplification devices hypothesized to improve speech communication in individuals with hypophonia (HP), as well as to identify individuals' device preferences. Method Twenty-two individuals with HP and their primary communication partners participated in a cross-over design study comparing three different speech amplification devices: a wired portable amplifier (Device A), a wireless stationary amplifier (Device B), and a one-way personal communication system (Device C). Participants attended one laboratory visit followed by 1-week trial periods with each device. At the first visit, HP participants completed speech tasks with and without the devices, in quiet and in noise. Following the in-laboratory test period, participants trialed each device at home for approximately 1 week per device. Following completion of the study, participants indicated whether or not they would like to continue using a device. Results Overall, in the presence of noise, all three devices demonstrated significant improvements in speech-to-noise levels and speech intelligibility compared to no device. A clear device hierarchy emerged such that the personal communication device (Device C) was associated with significantly better speech outcomes compared to the other two devices. The majority of participants elected to continue using a device at the completion of the study. Device preferences, however, did not clearly reflect the objective device hierarchy that was found for the objective speech measures. Each of the three devices was selected as a preferred device by at least three participants at the completion of the study. Conclusion Results from this study demonstrated clear differences in device performance in three distinct forms of amplification devices for individuals with HP. Findings suggest that amplification device use may be beneficial for this clinical population and underscore the potential to improve device availability and device selection criteria in future research. Supplemental Material https://doi.org/10.23641/asha.12735875.

Effects of Rate Manipulation on Intelligibility in Children With Cerebral Palsy

Purpose We evaluated the effects of a speech supplementation strategy to reduce rate and improve intelligibility in children with cerebral palsy. Method Twenty-five children with cerebral palsy (M _age = 12.08 years) completed a structured speaking task in 2 speech conditions: habitual speech and slow speech. Fifteen children had mild intelligibility deficits; 10 had moderate-severe intelligibility deficits. In each condition, children repeated utterances of 2-7 words in length. In the habitual speech condition, children used their natural and unaltered speaking rate. In the slow speech condition, children were cued to insert pauses between words. Intelligibility ratings were obtained from orthographic transcriptions by unfamiliar adult listeners (n = 100). Speech rate, in words per minute, was measured for each utterance. Results All children, regardless of severity group, were able to reduce their rate of speech when implementing the slow speech strategy. Only children in the moderate-severe group showed an improvement in intelligibility when implementing the slow speech strategy. Although there was considerable individual variability, there was a greater improvement in intelligibility for longer utterances compared to shorter ones. Conclusion A slow speech strategy may be beneficial for children with moderate-severe intelligibility deficits who speak in longer utterances. Future studies should seek to further examine the clinical feasibility of slow speech for children with reduced intelligibility.

Dysarthria Consequent to Cervical Spinal Cord Injury and Recurrent Laryngeal Nerve Damage: A Case Report

Objective

To assess and describe the involvement of all speech subsystems, including respiration, phonation, articulation, resonance, and prosody, in an individual with cervical spinal cord injury.

Methods

Detailed speech and voice assessment was performed that included Frenchay Dysarthria Assessment, cranial nerve examination, voice (per-ceptual and instrumental) and nasometric evalua-tion, and intelligibility and communicative effecti-veness.

Results

Impaired respiratory and phonatory con-trol correlated with the physical impairment of C4 and C5 prolapsed intervertebral disc. Cranial nerve examination indicated nerve IX and XI pathology. Phonatory deficits such as imprecise consonants and mild sibilant distortions were apparent. Voice analysis revealed a hoarse, breathy voice with re-duced loudness and no problems with resonance. Reading and speaking rate was reduced, and over-all a mild reduction in communicative effectiveness was perceived.

Conclusion

Assessment of the speech subsystems produced a comprehensive picture of the patient’s condition and impairments in one or more areas was identified. Treatment options to improve speech outcomes were provided.

Longitudinal Growth in Single Word Intelligibility Among Children With Cerebral Palsy From 24 to 96 Months of Age: Predicting Later Outcomes From Early Speech Production

Purpose Children with cerebral palsy (CP) are at risk for significant communication problems. Reduced speech intelligibility is common, even for those who do not have speech motor deficits. Development of intelligibility has not been comprehensively quantified in children with CP; as a result, we are currently unable to predict later speech outcomes. Such information would advance treatment decision making. We sought to examine growth in speech intelligibility among children with CP using a prospective longitudinal design, with a focus on age of crossing target intelligibility thresholds, age of greatest intelligibility growth, and how well intelligibility at 36 months predicted intelligibility at 96 months. Method Sixty-nine children with CP were followed longitudinally between 24 and 96 months of age. A total of 566 time points were examined across children ( M = 8.2 time points per child, SD = 2.6). We fitted a nonlinear random effects model for longitudinal observations and then used the fitted model trajectories to generate descriptive analyses of growth. We used results of the model to generate a set of simulations, which we analyzed to determine how well 36-month intelligibility data predicted 96-month data. Results Half of children crossed 25% and 50% intelligibility thresholds at 36 and 49 months of age, respectively. Slightly more than half of children did not reach 75% intelligibility by 96 months of age. Age of crossing 25%, 50%, and 75% intelligibility thresholds was highly negatively correlated with intelligibly at 96 months. Children had the steepest intelligibility growth at 36 months, followed by 48 and 60 months. Intelligibility at 36 months was highly predictive of intelligibility at 96 months. Conclusions The developmental window from 3 to 5 years constitutes a time of rapid growth in speech intelligibility in children with CP. Children who cross intelligibility thresholds of 25%, 50%, and 75% at earlier ages have better outcomes when they are older; early performance is highly predictive of later speech intelligibility outcomes. Children with CP as a group have delayed speech intelligibility development but are still growing through 96 months of age.

Acoustic and Perceptual Consequences of Speech Cues for Mandarin Speakers With Parkinson's Disease

Purpose This study investigated the effects of cueing for increased loudness and reduced speech rate on scaled intelligibility and acoustics of speech produced by Mandarin speakers with hypokinetic dysarthria due to Parkinson's disease (PD). Method Eleven speakers with PD read passages in habitual, loud, and slow speaking conditions. Fifteen listeners rated ease of understanding (EOU) of the speech samples on a visual analog scale. Effects of the cues on EOU, vocal loudness, pitch range, pause duration and frequency, articulation rate, and vowel space, as well as relationships between EOU gains and acoustic features, were analyzed. Results EOU increased significantly in the loud condition only. The loud cue resulted in increased intensity, and the slow cue resulted both in reduced articulation rate and increased pause frequency. In the loud condition, EOU increased significantly as intensity increased and vowel centralization decreased. In the slow condition, EOU tended to increase as intensity increased and vowel centralization decreased but did not reach statistical significance. Conclusion Cueing for loud speech may yield greater EOU gains than cueing for slow speech in Mandarin speakers with PD. Theoretical and clinical implications are discussed, although further investigations with more participants and a larger range of dysarthria severity are warranted.

Minimally Detectable Change and Minimal Clinically Important Difference of a Decline in Sentence Intelligibility and Speaking Rate for Individuals With Amyotrophic Lateral Sclerosis

PURPOSE

The purpose of this study was to determine the minimally detectable change (MDC) and minimal clinically important difference (MCID) of a decline in speech sentence intelligibility and speaking rate for individuals with amyotrophic lateral sclerosis (ALS). We also examined how the MDC and MCID vary across severities of dysarthria.

METHOD

One-hundred forty-seven patients with ALS and 49 healthy control subjects were selected from a larger, longitudinal study of bulbar decline in ALS, resulting in a total of 650 observations. Intelligibility and speaking rate in words per minute (WPM) were calculated using the Sentence Intelligibility Test (Yorkston, Beukelman, & Hakel, 2007), and the ALS Functional Rating Scale-Revised (Cedarbaum et al., 1999) was administered to capture patient perception of motor impairment. The MDC at the 95% confidence level was estimated using the following formula: MDC95 = 1.96 × √2 × SEM. For estimation of the MCID, receiver operating characteristic curves were generated, and area under the curve and optimal thresholds to maximize sensitivity and specificity were calculated.

RESULTS

The MDC for sentence intelligibility was 12.07%, and the MCID was 1.43%. The MDC for speaking rate was 36.57 WPM, and the MCID was 8.80 WPM. Both MDC and MCID estimates varied with severity of dysarthria.

CONCLUSIONS

The findings suggest that declines greater than 12% sentence intelligibility and 37 WPM are required to be outside measurement error and that these estimates vary widely across dysarthria severities. The MDC and MCID metrics used in this study to detect real and clinically relevant change should be estimated for other measures of speech outcomes in intervention research.

Static measurements of vowel formant frequencies and bandwidths: A review

PURPOSE

Data on vowel formants have been derived primarily from static measures representing an assumed steady state. This review summarizes data on formant frequencies and bandwidths for American English and also addresses (a) sources of variability (focusing on speech sample and time sampling point), and (b) methods of data reduction such as vowel area and dispersion.

METHOD

Searches were conducted with CINAHL, Google Scholar, MEDLINE/PubMed, SCOPUS, and other online sources including legacy articles and references. The primary search items were vowels, vowel space area, vowel dispersion, formants, formant frequency, and formant bandwidth.

RESULTS

Data on formant frequencies and bandwidths are available for both sexes over the lifespan, but considerable variability in results across studies affects even features of the basic vowel quadrilateral. Origins of variability likely include differences in speech sample and time sampling point. The data reveal the emergence of sex differences by 4 years of age, maturational reductions in formant bandwidth, and decreased formant frequencies with advancing age in some persons. It appears that a combination of methods of data reduction provide for optimal data interpretation.

CONCLUSION

The lifespan database on vowel formants shows considerable variability within specific age-sex groups, pointing to the need for standardized procedures.

Effects of Familiarization on Intelligibility of Dysarthric Speech in Older Adults With and Without Hearing Loss

PURPOSE

Familiarization tasks offer a promising platform for listener-targeted remediation of intelligibility disorders associated with dysarthria. To date, the body of work demonstrating improved understanding of dysarthric speech following a familiarization experience has been carried out on younger adults. The primary purpose of the present study was to examine the intelligibility effects of familiarization in older adults.

METHOD

Nineteen older adults, with and without hearing loss, completed a familiarization protocol consisting of three phases: pretest, familiarization, and posttest. The older adults' initial intelligibility and intelligibility improvement scores were compared with previously reported data collected from 50 younger adults (Borrie, Lansford, & Barrett, 2017a).

RESULTS

Relative to younger adults, initial intelligibility scores were significantly lower for older adults, although additional analysis revealed that the difference was limited to older adults with hearing loss. Key, however, is that irrespective of hearing status, the older and younger adults achieved comparable intelligibility improvement following familiarization (gain of roughly 20 percentage points).

CONCLUSION

This study extends previous findings of improved intelligibility of dysarthria following familiarization to a group of listeners who are critical to consider in listener-targeted remediation, namely, aging caregivers and/or spouses of individuals with dysarthria.

Receptive Vocabulary, Cognitive Flexibility, and Inhibitory Control Differentially Predict Older and Younger Adults' Success Perceiving Speech by Talkers With Dysarthria

PURPOSE

Previous research has demonstrated equivocal findings related to the effect of listener age on intelligibility ratings of dysarthric speech. The aim of the present study was to investigate the mechanisms that support younger and older adults' perception of speech by talkers with dysarthria.

METHOD

Younger and older adults identified words in phrases produced by talkers with dysarthria. Listeners also completed assessments on peripheral hearing, receptive vocabulary, and executive control functions.

RESULTS

Older and younger adults did not differ in their ability to perceive speech by talkers with dysarthria. Younger adults' success in identifying words produced by talkers with dysarthria was associated only with their hearing acuity. In contrast, older adults showed effects of working memory and cognitive flexibility and interactions between hearing acuity and receptive vocabulary and between hearing acuity and inhibitory control.

CONCLUSIONS

Although older and younger adults had equivalent performance identifying words produced by talkers with dysarthria, older adults appear to utilize more cognitive support to identify those words.

Predicting Intelligibility Gains in Individuals With Dysarthria From Baseline Speech Features

PURPOSE

Across the treatment literature, behavioral speech modifications have produced variable intelligibility changes in speakers with dysarthria. This study is the first of two articles exploring whether measurements of baseline speech features can predict speakers' responses to these modifications.

METHODS

Fifty speakers (7 older individuals and 43 speakers with dysarthria) read a standard passage in habitual, loud, and slow speaking modes. Eighteen listeners rated how easy the speech samples were to understand. Baseline acoustic measurements of articulation, prosody, and voice quality were collected with perceptual measures of severity.

RESULTS

Cues to speak louder and reduce rate did not confer intelligibility benefits to every speaker. The degree to which cues to speak louder improved intelligibility could be predicted by speakers' baseline articulation rates and overall dysarthria severity. Improvements in the slow condition could be predicted by speakers' baseline severity and temporal variability. Speakers with a breathier voice quality tended to perform better in the loud condition than in the slow condition.

CONCLUSIONS

Assessments of baseline speech features can be used to predict appropriate treatment strategies for speakers with dysarthria. Further development of these assessments could provide the basis for more individualized treatment programs.

Predicting Intelligibility Gains in Dysarthria Through Automated Speech Feature Analysis

PURPOSE

Behavioral speech modifications have variable effects on the intelligibility of speakers with dysarthria. In the companion article, a significant relationship was found between measures of speakers' baseline speech and their intelligibility gains following cues to speak louder and reduce rate (Fletcher, McAuliffe, Lansford, Sinex, & Liss, 2017). This study reexamines these features and assesses whether automated acoustic assessments can also be used to predict intelligibility gains.

METHOD

Fifty speakers (7 older individuals and 43 with dysarthria) read a passage in habitual, loud, and slow speaking modes. Automated measurements of long-term average spectra, envelope modulation spectra, and Mel-frequency cepstral coefficients were extracted from short segments of participants' baseline speech. Intelligibility gains were statistically modeled, and the predictive power of the baseline speech measures was assessed using cross-validation.

RESULTS

Statistical models could predict the intelligibility gains of speakers they had not been trained on. The automated acoustic features were better able to predict speakers' improvement in the loud condition than the manual measures reported in the companion article.

CONCLUSIONS

These acoustic analyses present a promising tool for rapidly assessing treatment options. Automated measures of baseline speech patterns may enable more selective inclusion criteria and stronger group outcomes within treatment studies.

Acoustic and perceptual speech characteristics of native Mandarin speakers with Parkinson's disease

This study examines acoustic features of speech production in speakers of Mandarin with Parkinson's disease (PD) and relates them to intelligibility outcomes. Data from 11 participants with PD and 7 controls are compared on several acoustic measures. In speakers with PD, the strength of association between these measures and intelligibility is investigated. Speakers with PD exhibited significant differences in fundamental frequency, pitch variation, vowel space, and rate relative to controls. However, in contrast to the English studies, speech rate was consistently slow and most strongly correlated with intelligibility. Thus, acoustic cues that strongly influence intelligibility in PD may vary cross-linguistically.