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Purpose: The impact of clear speech, increased vocal intensity, and rate reduction on acoustic characteristics of vowels was compared in speakers with Parkinson's disease (PD), speakers with multiple sclerosis (MS), and healthy controls. Method: Speakers read sentences in habitual, clear, loud, and slow conditions. Variations in clarity, intensity, and rate were stimulated using magnitude production. Formant frequency values for peripheral and nonperipheral vowels were obtained at 20%, 50%, and 80% of vowel duration to derive static and dynamic acoustic measures. Intensity and duration measures were obtained. Results: Rate was maximally reduced in the slow condition, and vocal intensity was maximized in the loud condition. The clear condition also yielded a reduced articulatory rate and increased intensity, although less than for the slow or loud conditions. Overall, the clear condition had the most consistent impact on vowel spectral characteristics. Spectral and temporal distinctiveness for peripheral-nonperipheral vowel pairs was largely similar across conditions. Conclusions: Clear speech maximized peripheral and nonperipheral vowel space areas for speakers with PD and MS while also reducing rate and increasing vocal intensity. These results suggest that a speech style focused on increasing articulatory amplitude yields the most robust changes in vowel segmental articulation.

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.

Researchers have generally assumed that listeners perceive speech compositionally, based on the combined processing of local acoustic–phonetic cues associated with individual linguistic units. Yet, these cue-based approaches have failed to fully account for variation in listeners’ identification of the words produced by a talker (i.e., variation in talker intelligibility). The current study adopts an alternative approach, estimating the perceptual representations used to process speech (the perceptual similarity space ) using the machine learning technique of self-supervised learning. We assessed intelligibility of 114 second-language (L2) English talkers and 25 L1 American English talkers through a speech-in-noise experiment (collecting data from ten L1 English listeners per talker, each transcribing 120 sentences). For each sample in a speech recording, we obtained a representation from a self-supervised learning model; the sequence of these representations forms a trajectory in the perceptual similarity space. The holistic distance between trajectories (two speakers’ productions of the same sentence) was analyzed. We found that for L2 talkers, the average distance between the trajectories of an L2 talker and the L1 American English talker group predicts relative intelligibility of a given L2 talker. Crucially, the distance measure predicted relative intelligibility among L2 talkers over and above a set of traditional acoustic–phonetic cues. Additionally, we found that the distance measure accounts for some of the relative intelligibility among L1 talkers. These results provide evidence that relative talker intelligibility is better captured with the perceptual similarity space approach, suggesting it is an appropriate tool to study variability in human speech production and perception.

To describe a new measure of functional intelligibility, the Intelligibility in Context Scale (ICS), and evaluate its validity, reliability, and sensitivity using 3 clinical measures of severity of speech sound disorder: (a) percentage of phonemes correct (PPC), (b) percentage of consonants correct (PCC), and (c) percentage of vowels correct (PVC). Speech skills of 120 preschool children (109 with parent-/teacher-identified concern about how they talked and made speech sounds and 11 with no identified concern) were assessed with the Diagnostic Evaluation of Articulation and Phonology (Dodd, Hua, Crosbie, Holm, & Ozanne, 2002). Parents completed the 7-item ICS, which rates the degree to which children's speech is understood by different communication partners (parents, immediate family, extended family, friends, acquaintances, teachers, and strangers) on a 5-point scale. Parents' ratings showed that most children were always (5) or usually (4) understood by parents, immediate family, and teachers, but only sometimes (3) by strangers. Factor analysis confirmed the internal consistency of the ICS items; therefore, ratings were averaged to form an overall intelligibility score. The ICS had high internal reliability (α = .93), sensitivity, and construct validity. Criterion validity was established through significant correlations between the ICS and PPC (r = .54), PCC (r = .54), and PVC (r = .36). The ICS is a promising new measure of functional intelligibility. These data provide initial support for the ICS as an easily administered, valid, and reliable estimate of preschool children's intelligibility when speaking with people of varying levels of familiarity and authority.

Auditory rhythms are ubiquitous in music, speech, and other everyday sounds. Yet, it is unclear how perceived rhythms arise from the repeating structure of sounds. For speech, it is unclear whether rhythm is solely derived from acoustic properties (e.g., rapid amplitude changes), or if it is also influenced by the linguistic units (syllables, words, etc.) that listeners extract from intelligible speech. Here, we present three experiments in which participants were asked to detect an irregularity in rhythmically spoken speech sequences. In each experiment, we reduce the number of possible stimulus properties that differ between intelligible and unintelligible speech sounds and show that these acoustically-matched intelligibility conditions nonetheless lead to differences in rhythm perception. In Experiment 1, we replicate a previous study showing that rhythm perception is improved for intelligible (16-channel vocoded) as compared to unintelligible (1-channel vocoded) speech–despite near-identical broadband amplitude modulations. In Experiment 2, we use spectrally-rotated 16-channel speech to show the effect of intelligibility cannot be explained by differences in spectral complexity. In Experiment 3, we compare rhythm perception for sine-wave speech signals when they are heard as non-speech (for naïve listeners), and subsequent to training, when identical sounds are perceived as speech. In all cases, detection of rhythmic regularity is enhanced when participants perceive the stimulus as speech compared to when they do not. Together, these findings demonstrate that intelligibility enhances the perception of timing changes in speech, which is hence linked to processes that extract abstract linguistic units from sound.

Identifying speech requires that listeners make rapid use of fine-grained acoustic cues—a process that is facilitated by being able to see the talker’s face. Face masks present a challenge to this process because they can both alter acoustic information and conceal the talker’s mouth. Here, we investigated the degree to which different types of face masks and noise levels affect speech intelligibility and subjective listening effort for young ( N  = 180) and older ( N  = 180) adult listeners. We found that in quiet, mask type had little influence on speech intelligibility relative to speech produced without a mask for both young and older adults. However, with the addition of moderate (− 5 dB SNR) and high (− 9 dB SNR) levels of background noise, intelligibility dropped substantially for all types of face masks in both age groups. Across noise levels, transparent face masks and cloth face masks with filters impaired performance the most, and surgical face masks had the smallest influence on intelligibility. Participants also rated speech produced with a face mask as more effortful than unmasked speech, particularly in background noise. Although young and older adults were similarly affected by face masks and noise in terms of intelligibility and subjective listening effort, older adults showed poorer intelligibility overall and rated the speech as more effortful to process relative to young adults. This research will help individuals make more informed decisions about which types of masks to wear in various communicative settings.

Binaural speech intelligibility in rooms is a complex process that is affected by many factors including room acoustics, hearing loss, and hearing aid (HA) signal processing. Intelligibility is evaluated in this paper for a simulated room combined with a simulated hearing aid. The test conditions comprise three spatial configurations of the speech and noise sources, simulated anechoic and concert hall acoustics, three amounts of multitalker babble interference, the hearing status of the listeners, and three degrees of simulated HA processing provided to compensate for the noise and/or hearing loss. The impact of these factors and their interactions is considered for normal-hearing (NH) and hearing-impaired (HI) listeners for sentence stimuli. Both listener groups showed a significant reduction in intelligibility as the signal-to-noise ratio (SNR) decreased, and showed a reduction in intelligibility in reverberation when compared to anechoic listening. There was no significant improvement in intelligibility for the NH group for the noise suppression algorithm used here, and no significant improvement in intelligibility for the HI group for more advanced HA processing algorithms as opposed to linear amplification in either of the two acoustic spaces or at any of the three SNRs.

Purpose: To further understand the effect of Parkinson's disease (PD) on articulatory movements in speech and to expand our knowledge of therapeutic treatment strategies, this study examined movements of the jaw, tongue blade, and tongue dorsum during sentence production with respect to speech intelligibility and compared the effect of varying speaking styles on these articulatory movements. Method: Twenty-one speakers with PD and 20 healthy controls produced 3 sentences under normal, loud, clear, and slow speaking conditions. Speech intelligibility was rated for each speaker. A 3-dimensional electromagnetic articulograph tracked movements of the articulators. Measures included articulatory working spaces, ranges along the first principal component, average speeds, and sentence durations. Results: Speakers with PD demonstrated significantly smaller jaw movements as well as shorter than normal sentence durations. Between-speaker variation in movement size of the jaw, tongue blade, and tongue dorsum was associated with speech intelligibility. Analysis of speaking conditions revealed similar patterns of change in movement measures across groups and articulators: larger than normal movement sizes and faster speeds for loud speech, increased movement sizes for clear speech, and larger than normal movement sizes and slower speeds for slow speech. Conclusions: Sentence-level measures of articulatory movements are sensitive to both disease-related changes in PD and speaking-style manipulations.

[Please see PDF for full article text] [Please see PDF for full article text] Objectives: To report the development and administration of the Saudi pediatric speech intelligibility (SPSI) test. Methods: This study was carried out at King Abdullah Ear Specialist Center, King Saud University, Riyadh, Saudi Arabia, between 2021 and 2023. A pilot study was carried out in 5 regions of Saudi Arabia including 100 normal hearing children aged 7-11 years old, with 20 children from each region. The final test materials were voice-recorded by a native Saudi radio announcer, and a software-based application for administering the SPSI was developed. Results: During the pilot study, minor adjustments were carried out to the test for more clarity. The developed SPSI software is an android-based application that includes features like automatic result calculation, data saving, and individual user accounts for examiners to review results. The SPSI test comprises 4-word cards and 2 sentence cards, each with 5 pictures, and operates in 3 modes: quiet, background noise, and competing sentences. Conclusion: The SPSI test has been developed in an android-based software using the Saudi local dialects. It can facilitate comprehensive and accurate assessment of speech intelligibility, particularly in children with hearing impairments. Keywords: Saudi pediatric speech intelligibility, speech test, hearing loss

The effects of muscle weakness on speech are currently not fully known. We investigated the relationships between maximum tongue pressure and second formant transition in adults with different types of dysarthria. It focused on the slope in the second formant transition because it reflects the tongue velocity during articulation. Sixty-three Japanese speakers with dysarthria (median age, 68 years; interquartile range, 58–77 years; 44 men and 19 women) admitted to acute and convalescent hospitals were included. Thirty neurologically normal speakers aged 19–85 years (median age, 22 years; interquartile range, 21.0–23.8 years; 14 men and 16 women) were also included. The relationship between the maximum tongue pressure and speech function was evaluated using correlation analysis in the dysarthria group. Speech intelligibility, the oral diadochokinesis rate, and the second formant slope were based on the impaired speech index. More than half of the speakers had mild to moderate dysarthria. Speakers with dysarthria showed significantly lower maximum tongue pressure, speech intelligibility, oral diadochokinesis rate, and second formant slope than neurologically normal speakers. Only the second formant slope was significantly correlated with the maximum tongue pressure (r = 0.368, p = 0.003). The relationship between the second formant slope and maximum tongue pressure showed a similar correlation in the analysis of subgroups divided by sex. The oral diadochokinesis rate, which is related to the speed of articulation, is affected by voice on/off, mandibular opening/closing, and range of motion. In contrast, the second formant slope was less affected by these factors. These results suggest that the maximum isometric tongue strength is associated with tongue movement speed during articulation.