Intelligibility In Dysarthria Research Articles

Vowel Acoustics as Predictors of Speech Intelligibility in Dysarthria.

This study sought to determine if alternative vowel space area (VSA) measures (i.e., novel trajectory-based measures: vowel space hull area and vowel space density) predicted speech intelligibility to the same extent as two traditional vowel measures (i.e., token-based measures: VSA and corner dispersion) in speakers with dysarthria. Additionally, this study examined if the strength of the relationship between acoustic vowel measures and intelligibility differed based on how intelligibility was measured (i.e., orthographic transcriptions [OTs] and visual analog scale [VAS] ratings). The Grandfather Passage was read aloud by 40 speakers with dysarthria of varying etiologies, including Parkinson's disease (n = 10), amyotrophic lateral sclerosis (n = 10), Huntington's disease (n = 10), and cerebellar ataxia (n = 10). Token- and trajectory-based acoustic vowel measures were calculated from the passage. Naïve listeners (N = 140) were recruited via crowdsourcing to provide OTs and VAS intelligibility ratings. Hierarchical linear regression models were created to model OTs and VAS intelligibility ratings using the acoustic vowel measures as predictors. Traditional VSA was the sole significant predictor of speech intelligibility for both the OTs (R 2 = .259) and VAS (R 2 = .236) models. In contrast, the trajectory-based measures were not significant predictors of intelligibility. Additionally, the OTs and VAS intelligibility ratings conveyed similar information. The findings suggest that traditional token-based vowel measures better predict intelligibility than trajectory-based measures. Additionally, the findings suggest that VAS methods are comparable to OT methods for estimating speech intelligibility for research purposes.

The Reliability and Validity of Speech-Language Pathologists' Estimations of Intelligibility in Dysarthria.

This study examined the reliability and validity of speech-language pathologists’ (SLP) estimations of speech intelligibility in dysarthria, including a visual analog scale (VAS) method and a percent estimation method commonly used in clinical settings. Speech samples from 20 speakers with dysarthria of varying etiologies were used to collect orthographic transcriptions from naïve listeners and VAS ratings and percent estimations of intelligibility from SLPs . Intra- and interrater reliability for the two SLP intelligibility measures were evaluated, and the relationship between these measures was assessed. Finally, linear regression was used to evaluate the relationship between the naïve listeners’ orthographic transcription scores and the two SLP intelligibility measures. The results indicated that the intrarater reliability for both SLP intelligibility measures was strong, and the interrater reliability between the SLP ratings was moderate to excellent. A moderate positive relationship between SLPs’ VAS ratings and percent estimations was also observed. Finally, both SLPs’ percent estimations and VAS ratings were predictive of naïve listeners’ orthographic transcription scores, with SLPs’ percent estimations being the strongest predictor. In conclusion, the average SLP percent estimations and VAS ratings are valid and reliable intelligibility measures. However, the validity and reliability of these measures vary between SLPs.

Picture Description in the Assessment of Connected Speech Intelligibility in Parkinson’s Disease: A Pilot Study

Introduction: Assessment of intelligibility in dysarthria tends to rely on oral reading of sentences or words. However, self-generated utterances are closer to a client's natural speech. This study investigated how transcription of utterances elicited by picture description can be used in the assessment of intelligibility in speakers with Parkinson’s disease. Methods: Speech samples from eleven speakers with Parkinson’s disease and six neurologically healthy persons were audio-recorded. Forty-two naive listeners completed transcriptions of self-generated sentences from a picture description task and orally read sentences from the Swedish Test of Intelligibility, as well as scaled ratings of narrative speech samples. Results: Intelligibility was higher in orally read than self-generated sentences and higher for content words than for the whole sentence in self-generated sentences for most of the speakers, although these within-group differences were not statistically significant at the group level. Adding contextual leads for the listeners increased intelligibility in self-generated utterances significantly but with individual variation. Although correlations between the intelligibility measures were at least moderate or strong, there was a considerable inter- and intra-speaker variability in intelligibility scores between tasks for the speakers with Parkinson’s disease, indicating individual variation of factors that impact intelligibility. Intelligibility scores from neurologically healthy speakers were generally high across tasks with no significant differences between the conditions. Conclusion: Within-speaker variability supports literature recommendations to use multiple methods and tasks when assessing intelligibility. The inclusion of transcription of self-generated utterances elicited by picture description to the intelligibility assessment has the potential to provide additional information to assessment methods based on oral reading of pre-scripted sentences and to inform the planning of interventions.

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

PurposeIndependent 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. MethodIntelligibility 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. ResultsIn 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. ConclusionThough 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.

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.

Assessment of intelligibility in dysarthria: development of a Maltese word and phrase list

ABSTRACTThis paper describes the development of the Maltese Intelligibility Lists (MIL) for the assessment of word and phrase intelligibility in dysarthria. Two main tools were employed: the Frenchay Dysarthria Assessment-2 (FDA), and the Maltese Language Resource Server (MLRS). Three main criteria served as the basis for the construction of the word and phrase lists: frequency of occurrence of Maltese phonemes, word frequency and an analysis of syllable types and structures. The most common 500 words in the MLRS corpus (Korpus Malti v. 3) were broadly transcribed and an analysis of different types of syllables and their frequency of occurrence was carried out. Based on this analysis, the relevant proportion of different syllable types required for the word and phrase lists for Maltese was calculated in line with the number of items present in the FDA-2. With regards to phoneme frequency, the words chosen demonstrate a similar short-vowel and consonant distribution as reported in a previous large-scale study. The MIL consists of 116 words and 50 phrases which are representative of Standard Maltese and can be used in the clinic to assess speech intelligibility in Maltese individuals with dysarthria.

Diphthong productions in speakers with Parkinson’s disease across speaking modes

Several vowel acoustics parameters (e.g., second formant frequency (F2) slope, vowel space area) are known to significantly contribute to speech intelligibility in dysarthria (Kim, Kent, Weismer, 2011; Lansford & Liss, 2014). Particularly, F2 slope has been identified as an important predictor of speech intelligibility regardless of underlying neuropathologies of dysarthria (Kim, Weismer, Kent & Duffy, 2009). The current study focuses on intra-speaker modifications of F2 slope in speakers with Parkinson’s disease (PD) voluntarily elicited across three speaking modes, less clear, conversational, and more clear speech, in recognition that prior work has mostly focused on inter-speaker comparisons. Varying speech clarity was our interest, given its wide use as an efficient behavioral therapeutic approach in clinic. Twenty speakers (10 PD, 10 neurologically healthy) were asked to read diphthongs embedded in real words. Diphthongs were chosen because they require a significant change in configuration of vocal tract and, therefore, are sensitive to the presence/severity of dysarthria. In the presentation, distributions of F2 slope 1) between PD and healthy speakers, and 2) across speaking modes within each speaker will be discussed. In addition, articulatory data will be presented for part of the speakers from whom kinematic data were obtained using the electromagnetic articulography (EMA) system.

Tongue- and jaw-specific contributions to increased vowel acoustic contrast in response to slow, loud, and clear speech in talkers with dysarthria

Slow, loud, and clear speech can elicit increased acoustic vowel contrast in talkers with dysarthria. However, articulator-specific changes in response to these speech modifications and their relative contribution to vowel acoustic changes remain poorly understood despite the fact that these three speech modulations are commonly used as speech treatments to increase intelligibility in dysarthria. This preliminary study examined tongue and jaw movements in talkers with Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS) using electromagnetic articulography. Participants repeated the phrase “See a kite again” five times under four speech conditions: typical, slow, loud, and clear speech. Tongue movements were decoupled from the jaw to determine the relative contribution of the jaw and tongue to the overall tongue composite movement during the diphthong /ai/ in “kite”. In the acoustic signal, the F2 minimum during /a/ and the F2 maximum during /i/ and their corresponding F1 values were extracted to calculate acoustic vowel contrast in F1-F2 vowel space. Linear regression analyses were used to determine tongue- and jaw-specific contributions to acoustic vowel contrast changes in response to these speech modifications. Data analysis is currently underway. We hypothesized that talkers with PD and ALS demonstrate different response patterns to these speech modifications.

The Impact of Contrastive Stress on Vowel Acoustics and Intelligibility in Dysarthria.

To compare vowel acoustics and intelligibility in words produced with and without contrastive stress by speakers with spastic (mixed-spastic) dysarthria secondary to cerebral palsy (DYSCP) and healthy controls (HCs). Fifteen participants (9 men, 6 women; age M = 42 years) with DYSCP and 15 HCs (9 men, 6 women; age M = 36 years) produced sentences containing target words with and without contrastive stress. Forty-five healthy listeners (age M = 25 years) completed a vowel identification task of DYSCP productions. Vowel acoustics were compared across stress conditions and groups using 1st (F1) and 2nd (F2) formant measures. Perceptual intelligibility was compared across stress conditions and dysarthria severity. F1 and F2 significantly increased in stressed words for both groups, although the degree of change differed. Mean Euclidian distance between vowels also increased with stress. The relative probability of vowels falling within the target F1 × F2 space was greater for HCs but did not differ with stress. Stress production resulted in greater listener vowel identification accuracy for speakers with mild dysarthria. Contrastive stress affected vowel formants for both groups. Perceptual results suggest that some speakers with dysarthria may benefit from a contrastive stress strategy to improve vowel intelligibility.

Familiarization Effects on Consonant Intelligibility in Dysarthric Speech

Background/Aims: This study investigates the effects of familiarization on naïve listeners' ability to identify consonants in dysarthric speech. Methods: A total of 120 listeners (30 listeners/speaker) participated in experiments over a 6-week period. Listeners were randomly assigned to one of the three familiarization conditions: a passive condition in which listeners heard audio recordings of words, an active condition in which listeners heard audio recordings of words while viewing the written material of words, and a control condition in which listeners had no exposure to the audio signal prior to identification tasks. Results: Familiarization improved naïve listeners' ability to identify consonants produced by a speaker with dysarthria. The active familiarization method exhibited an advantage over the other conditions, in terms of the magnitude and rapidness of improvement. One-month delayed test scores were higher than pre-familiarization scores, but the advantage of active familiarization was not present for all speakers. Conclusion: This study supports familiarization benefits in enhancing consonant intelligibility in dysarthria and suggests that perceptual learning mechanisms be harnessed for developing effective listener-oriented intervention techniques in the management of dysarthria. Current findings call for further research on a familiarization protocol that can subserve segmental learning with maximum efficacy.

Effects of listeners' working memory and noise on speech intelligibility in dysarthria

The purpose of this study was to investigate the effects of listeners' working memory (WM), types of noise and signal to noise ratios (SNRs) on speech intelligibility in dysarthria. Speech intelligibility was judged by using a word transcription task. A three-way mixed design (2 × 3 × 2) was used with the WM group (high/low group) as a between-subject factor and the types of noise (multi-talker babble/environmental noise) and SNRs (0, +10 and +20 dB) as within-subject factors. The dependent measure was the percentage of correctly transcribed words. The results revealed that the high WM group performed significantly better than the low WM group and listeners performed significantly better at higher levels of SNRs on the speech intelligibility test. The findings of this study suggested that listeners' cognitive abilities and SNRs should be considered as important factors when evaluating speech intelligibility in dysarthria.

Relationship between kinematics, F2 slope and speech intelligibility in dysarthria due to cerebral palsy

A multimodal approach combining acoustics, intelligibility ratings, articulography and surface electromyography was used to examine the characteristics of dysarthria due to cerebral palsy (CP). CV syllables were studied by obtaining the slope of F2 transition during the diphthong, tongue–jaw kinematics during the release of the onset consonant, and the related submental muscle activities and relating these measures to speech intelligibility. The results show that larger reductions of F2 slope are correlated with lower intelligibility in CP-related dysarthria. Among the three speakers with CP, the speaker with the lowest F2 slope and intelligibility showed smallest tongue release movement and largest jaw opening movement. The other two speakers with CP were comparable in the amplitude and velocity of tongue movements, but one speaker had abnormally prolonged jaw movement. The tongue–jaw coordination pattern found in the speakers with CP could be either compensatory or subject to an incompletely developed oromotor control system.

Acoustic characteristics of diphthongs in Parkinson's disease

The second formant frequency (F2) is sensitive to dysarthria. For example, vowel F2 slope has been shown to correlate with intelligibility, such that persons who are less intelligible or who have more severe speech impairment also tend to have shallower F2 slopes (Weismer etal., 1992). This result is consistent with studies suggesting the perceptual importance of transitions (Hillenbrand and Nearey, 1999), although the extent to which F2 slope explains reduced intelligibility in dysarthria is unclear. F2 slope also may serve as an acoustic metric of effort (Moon and Lindblom, 1994; Wouters and Macon, 2002). Therapeutic techniques for dysarthria, including Clear and Loud speech, are thought to be beneficial because they involve a scaling up of effort. Clear speech emphasizes hyperarticulation or increased articulatory effort, while Loud speech focuses on increasing respiratory–phonatory effort, although it has been suggested that increased loudness involves a system-wide scaling up of effort (Fox etal., 2006). Empirical evidence that Clear or Loud speech is associated with increased articulatory effort in dysarthria is limited. The current study sought to further evaluate this suggestion by investigating F2 slope characteristics for vowels produced in Habitual, Clear and Loud conditions by individuals with dysarthria secondary to Parkinson's disease.

Vowel Contrast and Speech Intelligibility in Dysarthria

Background/Aims: This study examined the spectral characteristics of American English vowels in dysarthria associated with cerebral palsy (CP), and investigated the relationship between a speaker’s overall speech intelligibility and vowel contrast. Methods: The data were collected from 12 American English native speakers (9 speakers with a diagnosis of CP and 3 controls). Primary measures were F₁ and F₂ frequencies of 3 corner vowels /i, a, u/ and 3 noncorner vowels /I, 3, */. Six acoustic variables were derived from the formant measures, and were regressed against intelligibility: corner vowel space, noncorner vowel space, mean distance between vowels, F₁ and F₂ variability, and overlap degree among vowels. Results: First, the effect of vowel was significant for both F₁ and F₂ measures for all speakers, but post hoc analysis revealed a reduced distinction at lower intelligibility. Second, regression functions relating intelligibility and acoustic variables were significant for overlap degree among vowels, F₁ variability, corner vowel space and mean distance between vowels. Overlap degree among vowels accounted for the greatest amount of variance in intelligibility scores. Conclusion: A speaker’s overall intelligibility in dysarthric speech is better represented by the overlap degree among vowels than by the vowel space.

Effect of Rate Control on Speech Production and Intelligibility in Dysarthria

The reported study investigated the effect of 7 rate control methods (RCM) on running speech intelligibility, speaking rate (SR), articulation rate (AR) and pause characteristics in 27 individuals with dysarthria. The data reveal that with the exception of slower on demand, each RCM resulted in lower mean SRs and ARs (p < 0.05). Clinically significant improvements in intelligibility were found in half of the participants with different types of dysarthria. The majority of them had normal or decreased ARs and SRs. The most effective methods were: alphabet board, hand tapping and pacing board. For the majority of speakers, the maximal decrease in speech rate was not associated with the maximal increase in intelligibility.

Speech technology‐based assessment of phoneme intelligibility in dysarthria

Currently, clinicians mainly rely on perceptual judgements to assess intelligibility of dysarthric speech. Although often highly reliable, this procedure is subjective with a lot of intrinsic variables. Therefore, certain benefits can be expected from a speech technology-based intelligibility assessment. Previous attempts to develop an automated intelligibility assessment mainly relied on automatic speech recognition (ASR) systems that were trained to recognize the speech of persons without known impairments. In this paper automatic speech alignment (ASA) systems are used instead. In addition, previous attempts only made use of phonemic features (PMF). However, since articulation is an important contributing factor to intelligibility of dysarthric speech and since phonological features (PLF) are shared by multiple phonemes, phonological features may be more appropriate to characterize and identify dysarthric phonemes. To investigate the reliability of objective phoneme intelligibility scores obtained by three types of intelligibility models: models using only phonemic features (yielded by an automated speech aligner) (PMF models), models using only phonological features (PLF models), and models using a combination of phonemic and phonological features (PMF + PLF models). Correlations were calculated between the objective phoneme intelligibility scores of 60 dysarthric speakers and the corresponding perceptual phoneme intelligibility scores obtained by a standardized perceptual phoneme intelligibility assessment. The correlations between the objective and perceptual intelligibility scores range from 0.793 for the PMF models, over 0.828 for PLF models to 0.943 for PMF + PLF models. The features selected to obtain such high correlations can be divided into six main subgroups: (1) vowel-related phonemic and phonological features, (2) lateral-related features, (3) silence-related features, (4) fricative-related features, (5) velar-related features and (6) plosive-related features. The phoneme intelligibility scores of dysarthric speakers obtained by the three investigated intelligibility model types are reliable. The highest correlation between the perceptual and objective intelligibility scores was found for models combining phonemic and phonological features. The intelligibility scoring system is now ready to be implemented in a clinical tool.

Effects of visible vs concealed alphabet cues on speech intelligibility in dysarthria

Aims Alphabet cues are often applied to improve communication with people with speech impairment. Uncertainty remains regarding which factors associated with the individual participant applying the technique (e.g. type and severity of dysarthria) or with the technique itself (e.g. visual letter information or altered speech output) impact on outcome. This study examined intelligibility of dysarthric speech with and without visible and concealed cues, and investigated the effects of word frequency, length and complexity on word recognition. Methods Twenty-two listeners transcribed words (n=120) of varying length (monosyllabic n=66, disyllabic n=54) and varying complexity (simple onset n=60, complex onset n=60) from an audiorecording of an adult with severe dysarthria associated with amyotrophic lateral sclerosis. Words were spoken with habitual speech, and with simultaneous pointing to the initial letter on an alphabet board (cueing). Intelligibility was tested in three listening conditions: habitual speech (with no cues), cued speech with alphabet cues visible to listeners and cued speech without alphabet cues visible to listeners. Findings In total, 46.6% of all the 120 words were correctly identified. Considering all items, visible cues increased intelligibility while concealed cues decreased intelligibility compared to the no cues condition. When examining word subsets, 30% of items with complex onsets and 38% of two-syllable items were correctly recognized. Higher word frequency facilitated recognition. Conclusions Visible cues significantly improved intelligibility however, not all words were equally facilitated. The possible issues around the implementation of cues associated with some neurological aetiologies are highlighted.

Telediagnostic assessment of intelligibility in dysarthria: A pilot investigation of MVP-online

BackgroundA most important index of functional impairment in dysarthria is intelligibility. The Munich Intelligibility Profile (MVP) is a computer-based method for the assessment of the intelligibility of dysarthric patients. A multi-user online version of MVP is now available. AimsTo describe the structure of MVP-online and to evaluate important psychometric features of the test. MethodsMVP-online was used in 200 test administrations (48 normal, 152 dysarthric). Intelligibility scores were based on 884 listening sessions (30 listeners). Various measures of listener agreement and of internal consistency were examined. ResultsNormal speakers achieved scores between 95% and 100% intelligible, the range for dysarthric patients was 20–100%. Test reliability turned out to be good when scores from 2 to 3 listeners were averaged. The amounts of long-term listener learning and of within-test listener adaptation were low. MVP-online proved to have a high internal consistency. ConclusionsMVP-online is an efficient, reliable and valid method for the assessment of intelligibility in dysarthria. It is useful for clinical standard diagnosis, for large-scale studies of speech motor impairment, and for longitudinal studies, e.g. in treatment research.Learning outcomes: The reader will be able to (1) understand the requirements to be met by clinical methods of intelligibility testing in the assessment of dysarthria, (2) evaluate the design of a new, computer-based rhyme test, (3) estimate the value of a tele-diagnostic approach in diagnosis, and (4) discuss the psychometric properties of intelligibility testing methods.

Effect of level of presentation on scaled speech intelligibility of speakers with dysarthria

A considerable amount of effort has been made to seek the acoustic correlates of reduced speech intelligibility in dysarthria, although some acoustic variables are under debate: For example, articulation rate, F2 slope, and vowel space have been frequently discussed in previous studies as acoustic predictors of speech intelligibility of dysarthria [Kim (2007)]. One variable that is not well understood, with respect to its effect on speech intelligibility in dysarthria, is level of presentation. This includes level generated by a speaker as well as level of presentation after the speaker has recorded utterances. Clearly, variations in level of presentation of recorded utterances will have some effect when an intelligibility test requires some segmental analysis (as in a minimal pairs test), but the potential effect when speech intelligibility is scaled is not so clear. This is an important question because of the frequent use of scaled intelligibility in dysarthria research. In this presentation, we will report data on how scaled speech intelligibility is affected by level of presentation of speech samples produced by speakers with various types and severity of dysarthria. [Work supported by NIH DC00319.]

Application of the ICF in Reduced Speech Intelligibility in Dysarthria

Regardless of the underlying neuromotor impairment, an almost universal consequence of dysarthria is a reduction in speech intelligibility. The purpose of this article is to examine critically and to discuss issues related directly to speech intelligibility in speakers with dysarthria. Reduced speech intelligibility resulting from dysarthria is examined using the World Health Organization's International Classification of Functioning, Disability and Health (ICF) conceptual framework. We propose that the ICF conceptual framework facilitates an awareness of the multidimensional nature of disablement. Furthermore, the ICF facilitates a broad understanding of the complex nature of dysarthria, ranging from the neuroanatomical and physiological substrates contributing to reduced speech intelligibility, to the effects of this type of communication disorder on an individual's functioning in society and beyond. Finally, a case example is presented that describes how the ICF can be applied to an individual with dysarthria and reduced speech intelligibility.