Speech Intelligibility For Individuals Research Articles

Altered Auditory Feedback Improves Speech Intelligibility in Individuals Diagnosed with Parkinson’s Disease: A Pilot Study

Introduction: The purpose of the current study was to evaluate speech intelligibility and speech rate in individuals with Parkinson’s disease using altered auditory feedback (AAF) in comparison to age-matched healthy controls. Based on prior research, it is hypothesized that the use of AAF will improve participants’ speech intelligibility. Methods: Five individuals with Parkinson’s disease (clinical group) and five age-matched healthy controls aged 50 years and above participated in this pre-/post-group experiment. All participants completed reading and monologue tasks with and without AAF. The AAF delayed the participants’ auditory feedback by 150 ms and altered it by 1/20 octave. Thirty-two naïve listeners listened to the recorded participants’ speech samples (with and without AAF) randomly and rated the participants’ speech intelligibility. Results: Results of the mixed model ANOVA revealed that participants in the control group had significantly higher speech intelligibility scores than the participants in the clinical group. Post hoc tests indicated that only participants in the clinical group were more intelligible with AAF than without AAF. Participants in the clinical group had better speech intelligibility when reading the passage than speaking the monologue. With regards to speech rate, participants spoke more slowly with AAF than without. Finally, there was a negative correlation between speech rate and speech intelligibility. Discussion: The current findings support our hypothesis that AAF improves speech intelligibility in people with Parkinson’s disease, though not in healthy controls. Future research should evaluate the long-term effect of AAF use on speech intelligibility in people with Parkinson’s disease.

A Transparent Mask and Clear Speech Benefit Speech Intelligibility in Individuals With Hearing Loss.

The purpose of the study is to investigate the impacts of a surgical mask and a transparent mask on audio-only and audiovisual speech intelligibility in noise (i.e., 0 dB signal-to-noise ratio) in individuals with mild-to-profound hearing loss. The study also examined if individuals with hearing loss can benefit from using a transparent mask and clear speech for speech understanding in noise. Thirty-one individuals with hearing loss (from 22 to 74 years old) completed keyword identification tasks to measure face-masked speech intelligibility in noise. A mixed-effects logistic regression model was used to examine the effects of face masks (no mask, transparent mask, surgical mask), presentation modes (audio only, audiovisual), speaking styles (conversational, clear), noise type (speech-shaped noise [SSN], four-talker babble [4-T babble]), hearing groups (mild hearing loss [MHL], greater than MHL: GHL), and their interactions on binary accuracy of keyword identification. In the audio-only mode, the GHL group showed reduced speech intelligibility regardless of other factors, whereas the MHL group showed decreased speech intelligibility for the transparent mask more than for the surgical mask. The use of a transparent mask was advantageous for both hearing loss groups. Clear speech remediated the detrimental effects of face masks on speech intelligibility in noise. Both groups tended to perform better in SSN versus 4-T babble. The findings indicate that, when using face masks, either a transparent mask or a surgical mask negatively affects speech understanding in noise for individuals with hearing loss. Using a transparent mask and clear speech could be a potential solution to improve speech intelligibility in communication with face masks in noise.

Speech treatment for Hebrew-speaking adolescents and young adults with developmental dysarthria: A comparison of mSIT and Beatalk.

Individuals with developmental dysarthria typically demonstrate reduced functioning of one or more of the speech subsystems, which negatively impacts speech intelligibility and communication within social contexts. A few treatment approaches are available for improving speech production and intelligibility among individuals with developmental dysarthria. However, these approaches have only limited application and research findings among adolescents and young adults. To determine and compare the effectiveness of two treatment approaches, the modified Speech Intelligibility Treatment (mSIT) and the Beatalk technique, on speech production and intelligibility among Hebrew-speaking adolescents and young adults with developmental dysarthria. Two matched groups of adolescents and young adults with developmental dysarthria participated in the study. Each received one of the two treatments, mSIT or Beatalk, over the course of 9 weeks. Measures of speech intelligibility, articulatory accuracy, voice and vowel acoustics were assessed both pre- and post-treatment. Both the mSIT and Beatalk groups demonstrated gains in at least some of the outcome measures. Participants in the mSIT group exhibited improvement in speech intelligibility and voice measures, while participants in the Beatalk group demonstrated increased articulatory accuracy and gains in voice measures from pre- to post-treatment. Significant increases were noted post-treatment for first formant values for select vowels. Results of this preliminary study are promising for both treatment approaches. The differentiated results indicate their distinct application to speech intelligibility deficits. The current findings also hold clinical significance for treatment among adolescents and young adults with motor speech disorders and application for a language other than English. What is already known on the subject Developmental dysarthria (e.g., secondary to cerebral palsy) is a motor speech disorder that negatively impacts speech intelligibility, and thus communication participation. Select treatment approaches are available with the aim of improving speech intelligibility in individuals with developmental dysarthria; however, these approaches are limited in number and have only seldomly been applied specifically to adolescents and young adults. What this paper adds to existing knowledge The current study presents preliminary data regarding two treatment approaches, the mSIT and Beatalk technique, administered to Hebrew-speaking adolescents and young adults with developmental dysarthria in a group setting. Results demonstrate the initial effectiveness of the treatment approaches, with different gains noted for each approach across speech and voice domains. What are the potential or actual clinical implications of this work? The findings add to the existing literature on potential treatment approaches aiming to improve speech production and intelligibility among individuals with developmental dysarthria. The presented approaches also show promise for group-based treatments as well as the potential for improvement among adolescents and young adults with motor speech disorders.

Speech intelligibility loss due to amyotrophic lateral sclerosis: the effect of tongue movement reduction on vowel and consonant acoustic features

ABSTRACT The purpose of this study was to identify aspects of impaired tongue motor performance that limit the ability to produce distinct speech sounds and contribute to reduced speech intelligibility in individuals with dysarthria secondary to amyotrophic lateral sclerosis (ALS). We analyzed simultaneously recorded tongue kinematic and acoustic data from 22 subjects during three target words (cat, dog, and took). The subjects included 11 participants with ALS and 11 healthy controls from the X-ray microbeam dysarthria database (Westbury, 1994). Novel measures were derived based on the range and speed of relative movement between two quasi-independent regions of the tongue – blade and dorsum – to characterize the global pattern of tongue dynamics. These “whole tongue” measures, along with the range and speed of single tongue regions, were compared across words, groups (ALS vs. control), and measure types (whole tongue vs. tongue blade vs. tongue dorsum). Reduced range and speed of both global and regional tongue movements were found in participants with ALS relative to healthy controls, reflecting impaired tongue motor performance in ALS. The extent of impairment, however, varied across words and measure types. Compared with the regional tongue measures, the whole tongue measures showed more consistent disease-related changes across the target words and were more robust predictors of speech intelligibility. Furthermore, these whole tongue measures were correlated with various word-specific acoustic features associated with intelligibility decline in ALS, suggesting that impaired tongue movement likely contributes to reduced phonetic distinctiveness of both vowels and consonants that underlie speech intelligibility decline in ALS.

Korean Clear Speech Improves Speech Intelligibility for Individuals with Normal Hearing and Individuals with Hearing Loss.

Clear speech is an effective communication strategy to improve speech intelligibility. While clear speech in several languages has been shown to significantly benefit intelligibility among listeners with differential hearing sensitivities and across environments of different noise levels, whether these results apply to Korean clear speech is unclear on account of the language's unique acoustic and linguistic characteristics. This study aimed to measure the intelligibility benefits of Korean clear speech relative to those of conversational speech among listeners with normal hearing and hearing loss. We used a mixed-model design that included both within-subject (effects of speaking style and listening condition) and between-subject (hearing status) elements. We compared the rationalized arcsine unit scores, which were transformed from the number of keywords recognized and repeated, between clear and conversational speech in groups with different hearing sensitivities across five listening conditions (quiet and 10, 5, 0, and -5 dB signal-to-noise ratio) using a mixed model analysis. The intelligibility scores of Korean clear speech were significantly higher than those of conversational speech under most listening conditions in all groups; the former yielded increases of 6 to 32 rationalized arcsine units in intelligibility. The present study provides information on the actual benefits of Korean clear speech for listeners with varying hearing sensitivities. Audiologists or hearing professionals may use this information to establish communication strategies for Korean patients with hearing loss.

Effects of an intensive voice treatment on articulatory function and speech intelligibility in children with motor speech disorders: A phase one study

Producing speech that is clear, audible, and intelligible to others is a challenge for many children with cerebral palsy (CP) and children with Down syndrome (DS). Previous studies have demonstrated the effectiveness of using the Lee Silverman Voice Treatment (LSVT LOUD®) to increase vocal loudness and improve speech intelligibility in individuals with dysarthria secondary to Parkinson’s disease (PD), and some research suggests that it also may be effective for individuals with dysarthria secondary to other conditions, including CP and DS. Although LSVT LOUD targets healthy vocal loudness, there is some evidence of spreading effects to the articulatory system. Acoustic data from two groups of children with secondary motor speech disorders [one with CP (n = 17) and one with DS (n = 9)] who received a full dose of LSVT LOUD and for whom post-treatment intelligibility gains have been previously reported, were analyzed for treatment effects on: 1) vowel duration, 2) acoustic vowel space and 3) the ratio of F2/i/ to F2/u/. Statistically significant changes in vowel duration and acoustic vowel space occurred pre-treatment to 12 weeks post-treatment in the CP group, and increased acoustic vowel space was observed in 5 of the DS participants. The present study provides preliminary evidence of intensive voice treatment spreading effects to the articulatory system in some children with CP and children with DS consistent with previous findings in other populations.

Influence of transient pressure changes on speech intelligibility: Implications for next-generation train travel.

High-speed trains are operated in increasingly complex railway networks and continual improvement of driver assistance systems is necessary to maintain safety. Speech offers the opportunity to provide information to the driver without disrupting visual attention. However, it is not known whether the transient pressure changes inside trains passing through tunnels interfere with speech intelligibility. Our primary goal was to test whether the most severe pressure variations occurring in high-speed trains (25 hPa in 2 s) affect speech intelligibility in individuals with normal hearing ability and secondly whether a potential effect would depend on the direction of the pressure change. A cross-over design was used to compare speech intelligibility, measured with the monosyllable word test by Wallenberg and Kollmeier, in steady ambient pressure versus subsequent to pressure events, both realised in a pressure chamber. Since data for a power calculation did not exist, we conducted a pilot study with 20 participants to estimate variance of intra-individual differences. The upper 80% confidence limit guided sample size of the main campaign, which was performed with 72 participants to identify a 10% difference while limiting alpha (5%) and beta error (10%). On average, a participant understood 0.7 fewer words following a pressure change event compared to listening in steady ambient pressure. However, this intra-individual differences varied strongly between participants, standard deviation (SD) ± 4.5 words, resulting in a negligible effect size of 0.1 and the Wilcoxon signed rank test (Z = -1.26; p = 0.21) did not distinguish it from chance. When comparing decreasing and increasing pressure events an average of 0.2 fewer words were understood (± 3.9 SD). The most severe pressure changes expected to occur in high-speed trains passing through tunnels do not interfere with speech intelligibility and are in itself not a risk factor for loss of verbal information transmission.

A Cross-Language Study of Acoustic Predictors of Speech Intelligibility in Individuals With Parkinson's Disease.

The present study aimed to compare acoustic models of speech intelligibility in individuals with the same disease (Parkinson's disease [PD]) and presumably similar underlying neuropathologies but with different native languages (American English [AE] and Korean). A total of 48 speakers from the 4 speaker groups (AE speakers with PD, Korean speakers with PD, healthy English speakers, and healthy Korean speakers) were asked to read a paragraph in their native languages. Four acoustic variables were analyzed: acoustic vowel space, voice onset time contrast scores, normalized pairwise variability index, and articulation rate. Speech intelligibility scores were obtained from scaled estimates of sentences extracted from the paragraph. The findings indicated that the multiple regression models of speech intelligibility were different in Korean and AE, even with the same set of predictor variables and with speakers matched on speech intelligibility across languages. Analysis of the descriptive data for the acoustic variables showed the expected compression of the vowel space in speakers with PD in both languages, lower normalized pairwise variability index scores in Korean compared with AE, and no differences within or across language in articulation rate. The results indicate that the basis of an intelligibility deficit in dysarthria is likely to depend on the native language of the speaker and listener. Additional research is required to explore other potential predictor variables, as well as additional language comparisons to pursue cross-linguistic considerations in classification and diagnosis of dysarthria types.

Effects of audio-visual information on the intelligibility of alaryngeal speech

Background There is minimal research on the contribution of visual information on speech intelligibility for individuals with a laryngectomy (IWL). Aims The purpose of this project was to determine the effects of mode of presentation (audio-only, audio-visual) on alaryngeal speech intelligibility. Method Twenty-three naïve listeners were randomly presented 176 phonemically balanced sentences produced by three alaryngeal (tracheoesophageal, esophageal, electrolaryngeal) and one typical, laryngeal speaker in both audio-only and audio-visual modes of presentation. Results Overall, results showed a small (3%) but statistically significant higher speech intelligibility score for audio-visual stimuli compared to audio-only stimuli as well as a significant interaction effect between mode of speech and mode of presentation. Within mode of speech, electrolaryngeal speech was the only mode that benefited significantly from the inclusion of visual information (10% increase). Overall intelligibility showed similar patterns both within audio-only and audio-visual modes of presentation: typical laryngeal and tracheoesophageal speech modes were significantly more intelligible than both esophageal and electrolaryngeal. Conclusions Results suggest that listeners may benefit more from visual information from speakers with poor baseline speech intelligibility. Results also show similar intelligibility between typical, laryngeal and tracheoesophageal modes of speech. Results should be interpreted with caution, however, as only one speaker from each mode of speech was included. Further research is required to determine the nature of the increase. Learning outcomes: Readers will (1) increase their understanding of the potential impact of visual information in the perception of alaryngeal speech; (2) identify potential factors that may augment or hinder speech perception; and (3) discuss how individual modes of alaryngeal speech may be affected by audio-visual information.

Effects of orofacial myofunctional therapy on speech intelligibility in individuals with persistent articulatory impairments

This study examined the effects of orofacial myofunctional therapy (OMT) on speech intelligibility in adults with persistent articulation impairments. Six adults in the age range of 18-23 years were selected to receive orofacial myofunctional therapy for a period of six weeks. The results showed that five out of six clients made significant progress in oral postures and speech sound production across all three speech production tasks: single words, sentences, and spontaneous speech. Speech intelligibility increased significantly in all clients except the one diagnosed with developmental apraxia of speech. Orofacial myofunctional therapists, speech-language pathologists, and other professionals need to rule out underlying orofacial myofunctional variables when targeting speech sounds for intervention. Speech production tasks may be considered as important measures to understand the efficacy of OMT in clinical settings.

The effect of compression and attention allocation on speech intelligibility. II

Previous investigations of the effects of amplitude compression on measures of speech intelligibility have shown inconsistent results. Recently, a novel paradigm was used to investigate the possibility of more consistent findings with a measure of speech perception that is not based entirely on intelligibility (Choi and Carrell, 2003). That study exploited a dual-task paradigm using a pursuit rotor online visual-motor tracking task (Dlhopolsky, 2000) along with a word repetition task. Intensity-compressed words caused reduced performance on the tracking task as compared to uncompressed words when subjects engaged in a simultaneous word repetition task. This suggested an increased cognitive load when listeners processed compressed words. A stronger result might be obtained if a single resource (linguistic) is required rather than two (linguistic and visual-motor) resources. In the present experiment a visual lexical decision task and an auditory word repetition task were used. The visual stimuli for the lexical decision task were blurred and presented in a noise background. The compressed and uncompressed words for repetition were placed in speech-shaped noise. Participants with normal hearing and vision conducted word repetition and lexical decision tasks both independently and simultaneously. The pattern of results is discussed and compared to the previous study.

The effect of compression and attention allocation on speech intelligibility

Research investigating the effects of amplitude compression on speech intelligibility for individuals with sensorineural hearing loss has demonstrated contradictory results [Souza and Turner (1999)]. Because percent-correct measures may not be the best indicator of compression effectiveness, a speech intelligibility and motor coordination task was developed to provide data that may more thoroughly explain the perception of compressed speech signals. In the present study, a pursuit rotor task [Dlhopolsky (2000)] was employed along with word identification task to measure the amount of attention required to perceive compressed and non-compressed words in noise. Monosyllabic words were mixed with speech-shaped noise at a fixed signal-to-noise ratio and compressed using a wide dynamic range compression scheme. Participants with normal hearing identified each word with or without a simultaneous pursuit-rotor task. Also, participants completed the pursuit-rotor task without simultaneous word presentation. It was expected that the performance on the additional motor task would reflect effect of the compression better than simple word-accuracy measures. Results were complex. For example, in some conditions an irrelevant task actually improved performance on a simultaneous listening task. This suggests there might be an optimal level of attention required for recognition of monosyllabic words.

Implementing Speech Supplementation Strategies

A growing body of experimental research suggests that speech supplementation strategies can markedly increase speech intelligibility for individuals with dysarthria (D. Beukelman & K. Yorkston, 1977; E. Crow & P. Enderby, 1989; L. Hunter, T. Pring, & S. Martin, 1991; K. C. Hustad & D. R. Beukelman, 2001). However, studies in which speech supplementation strategies were actually implemented by speakers with dysarthria are limited, leaving their clinical efficacy unknown. The present study compared intelligibility and speech rate differences following speaker implementation of 3 strategies (topic, alphabet, and combined topic and alphabet supplementation) and a habitual (noncued) speech control condition for 5 speakers with severe dysarthria. Results revealed that combined cues and alphabet cues yielded significantly higher intelligibility scores and slower speech rates than topic cues and noncued speech. Overall, topic cues and noncued speech did not differ from one another with regard to intelligibility or speech rate. Combined cues and alphabet cues did not differ from one another with regard to intelligibility; however, speech rate was significantly different between the 2 strategies. Individual differences among speakers were generally consistent with group findings. Results were somewhat different from previous research in which strategies were experimentally superimposed on the habitual speech signal. However, findings provide evidence that alphabet cues and combined cues can have an important effect on intelligibility for speakers with severe dysarthria.

The correlation of vowel space and speech intelligibility for individuals with cerebral palsy

The relationship between the area of the vowel space (F1/F2 space) and speech intelligibility was studied in a group of 20 Mandarin-Chinese-speaking young adults with cerebral palsy. Subjects read aloud 18 bisyllabic words containing the vowels /i/, /a/, and /u/ using their habitual speaking rate. The words were identified by three normal listeners and the percent corrects of vowel identifications were used as speech intelligibility for the individual cerebral-palsied speakers. Results revealed that cerebral-palsied speakers’ intelligibility varied greatly across individuals (scores ranged from 36% to 100%). Speakers with cerebral palsy exhibited smaller vowel space areas when compared to 10 age-matched controls. The correlation between vowel space area and speech intelligibility was significant (r=0.612, p<0.005). Cerebral-palsied speakers with larger vowels spaces were generally more intelligible than speakers with reduced vowel spaces. These results suggest that vowel space area can serve as an important component of overall estimates of speech intelligibility, and will be related to data collected in studies comparing infant-directed (ID) versus adult-directed (AD) speech, which show that speakers use significantly larger vowel areas when engaged in ID speech. [Work funded by NIH, HFSP, and the Talaris Research Institute.]