Control of voice-onset time in the absence of hearing: a review

Discrimination and sensorimotor adaptation of self-produced vowels in cochlear implant users

Humans rely on auditory feedback to monitor and adjust their speech for clarity. Cochlear implants (CIs) have helped over a million people restore access to auditory feedback, which significantly improves speech production. However, there is substantial variability in outcomes. This study investigates the extent to which CI users can use their auditory feedback to detect self-produced sensory errors and make adjustments to their speech, given the coarse spectral resolution provided by their implants. First, we used an auditory discrimination task to assess the sensitivity of CI users to small differences in formant frequencies of their self-produced vowels. Then, CI users produced words with altered auditory feedback in order to assess sensorimotor adaptation to auditory error. Almost half of the CI users tested can detect small, within-channel differences in their self-produced vowels, and they can utilize this auditory feedback towards speech adaptation. An acoustic hearing control group showed better sensitivity to the shifts in vowels, even in CI-simulated speech, and elicited more robust speech adaptation behavior than the CI users. Nevertheless, this study confirms that CI users can compensate for sensory errors in their speech and supports the idea that sensitivity to these errors may relate to variability in production.

Interarticulator Speech Coordination: Timing Is of the Essence

PURPOSE

In skilled speech production, sets of articulators, such as the jaw, tongue, and lips, work cooperatively to achieve task-specific movement goals, despite rampant contextual variation. Efforts to understand these functional units, termed coordinative structures, have focused on identifying the essential control parameters responsible for allowing articulators to achieve these goals, with some research focusing on temporal parameters (relative timing of movements) and other research focusing on spatiotemporal parameters (phase angle of movement onset for one articulator, relative to another). Here, both types of parameters were investigated and compared in detail.

METHOD

Ten talkers recorded nonsense, disyllabic /tV#Cat/ utterances using electromagnetic articulography, with alternative V (/ɑ/-/ɛ/) and C (/t/-/d/), across variation in rate (fast-slow) and stress (first syllable stressed-unstressed). Two measures were obtained: (a) the timing of tongue-tip raising onset for medial C, relative to jaw opening-closing cycles and (b) the angle of tongue-tip raising onset, relative to the jaw phase plane.

RESULTS

Results showed that any manipulation that shortened the jaw opening-closing cycle reduced both the relative timing and phase angle of the tongue-tip movement onset, but relative timing of tongue-tip movement onset scaled more consistently with jaw opening-closing across rate and stress variation.

CONCLUSION

These findings suggest the existence of an intrinsic timing mechanism (or "central clock") that is the primary control parameter for coordinative structures, with online compensation then allowing these structures to achieve their goals spatially.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.22144259.

VOT y VOT ratio en hispanohablantes con Enfermedad de Parkinson

El Voice Onset Time (VOT) es una medida acústica que hace referencia a la diferencia entre el tiempo de la liberación de la oclusión y el inicio de la vibración de las cuerdas vocales en los sonidos oclusivos; el VOT ratio (VOTr), por su parte, se refiere a la relación entre el VOT y la duración de la sílaba que busca modelar el efecto de la velocidad del habla sobre el VOT. Ambas medidas han sido estudiadas en hablantes con Enfermedad de Parkinson (EP) en tareas de habla experimentales, pero existen pocos trabajos en personas con EP que sean hispanohablantes y en el contexto de habla conectada. En este estudio se investigó el comportamiento del VOT y VOTr en habla conectada en hispanohablantes colombianos con EP. Mediante el software Praat se calculó el VOT y VOTr de los sonidos /p, b, t, d, k, g/ en grabaciones tomadas del corpus PC-GITA que correspondían a 50 personas con EP y 50 sin EP pareadas por edad y sexo. Se encontró que, con algunas variaciones, el VOT y el VOTr en habla conectada se comportan de manera similar entre sí y respecto a otros contextos de análisis previamente estudiados; comparado con el grupo control, se hallaron diferencias en las personas con EP, pero estas solamente fueron significativas en el VOT y VOTr de /p/, que fue más largo para las mujeres con EP(p < .05) así como en el VOT y VOTr de /d/ para ambos sexos con EP, pues fueron menores(p ≤ .05). Las diferencias relacionadas con el sexo solamente estuvieron entre hombres y mujeres con EP en el VOT de /p/, que fue más largo en las mujeres (p < .05). Esta evidencia podría indicar que en español, en habla conectada, el VOT y el VOTr son igual de sensibles a los cambios en el VOT asociados a la EP y al parecer el sexo no tiene un efecto significativo sobre ellas.

The Relationship Between Voice Onset Time and Increase in Vocal Effort and Fundamental Frequency

Purpose Prior work suggests that voice onset time (VOT) may be impacted by laryngeal tension: VOT means decrease when individuals with typical voices increase their fundamental frequency (f o) and VOT variability is increased in individuals with vocal hyperfunction, a voice disorder characterized by increased laryngeal tension. This study further explored the relationship between VOT and laryngeal tension during increased f o, vocal effort, and vocal strain. Method Sixteen typical speakers of American English were instructed to produce VOT utterances under four conditions: baseline, high pitch, effort, and strain. Repeated-measures analysis of variance models were used to analyze the effects of condition on VOT means and standard deviations (SDs); pairwise comparisons were used to determine significant differences between conditions. Results Voicing, condition, and their interaction significantly affected VOT means. Voiceless VOT means significantly decreased for high pitch (p < .001) relative to baseline; however, no changes in voiceless VOT means were found for effort or strain relative to baseline. Although condition had a significant effect on VOT SDs, there were no significant differences between effort, strain, and high pitch conditions relative to baseline. Conclusions Speakers with typical voices likely engage different musculature to increase pitch than to increase vocal effort and strain. The increased VOT variability present with vocal hyperfunction is not seen in individuals with typical voices using increased effort and strain, supporting the assertion that this feature of vocal hyperfunction may be related to disordered vocal motor control rather than resulting from effortful voice production.

Age-related and noise-induced hearing loss alters grasshopper mouse (Onychomys) vocalizations

Age-related and noise-induced hearing loss disorders are among the most common pathologies affecting Americans across their lifespans. Loss of auditory feedback due to hearing disorders is correlated with changes in voice and speech-motor control in humans. Although rodents are increasingly used to model human age- and noise-induced hearing loss, few studies have assessed vocal changes after acoustic trauma. Northern grasshopper mice (Onychomys leucogaster) represent a candidate model because their hearing sensitivity is matched to the frequencies of long-distance vocalizations that are produced using vocal fold vibrations similar to human speech. In this study, we quantified changes in auditory brainstem responses (ABRs) and vocalizations related to aging and noise-induced acoustic trauma. Mice showed a progressive decrease in hearing sensitivity across 4-32 kHz, with males losing hearing more rapidly than females. In addition, noise-exposed mice had a 61.55 dB SPL decrease in ABR sensitivity following a noise exposure, with some individuals exhibiting a 21.25 dB recovery 300-330 days after noise exposure. We also found that older grasshopper mice produced calls with lower fundamental frequency. Sex differences were measured in duration of calls with females producing longer calls with age. Our findings indicate that grasshopper mice experience age- and noise- induced hearing loss and concomitant changes in vocal output, making them a promising model for hearing and communication disorders.

Voice Onset Time in Individuals With Hyperfunctional Voice Disorders: Evidence for Disordered Vocal Motor Control

Purpose This study examined vocal hyperfunction (VH) using voice onset time (VOT). We hypothesized that speakers with VH would produce shorter VOTs, indicating increased laryngeal tension, and more variable VOTs, indicating disordered vocal motor control. Method We enrolled 32 adult women with VH (aged 20-74 years) and 32 age- and sex-matched controls. All were speakers of American English. Participants produced vowel-consonant-vowel combinations that varied by vowel (ɑ/u) and plosive (p/b, t/d, k/g). VOT-measured at the release of the plosive to the initiation of voicing-was averaged over three repetitions of each vowel-consonant-vowel combination. The coefficient of variation (CoV), a measure of VOT variability, was also computed for each combination. Results The mean VOTs were not significantly different between the two groups; however, the CoVs were significantly greater in speakers with VH compared to controls. Voiceless CoV values were moderately correlated with clinical ratings of dysphonia (r = .58) in speakers with VH. Conclusion Speakers with VH exhibited greater variability in phonemic voicing targets compared to vocally healthy speakers, supporting the hypothesis for disordered vocal motor control in VH. We suggest future work incorporate VOT measures when assessing auditory discrimination and auditory-motor integration deficits in VH.

Influence of Oral Morphology on Speech Production in Subjects Wearing Maxillary Removable Partial Dentures with Major Connectors

BACKGROUND/AIMS

Speech impairment during the initial phase of removable partial denture (RPD) treatment can prevent patient adaptation to RPDs. This study was undertaken to investigate the influence of oral morphology on speech production in subjects wearing RPDs with major connectors.

METHODS

Two types of connectors were fabricated for 17 subjects with normal dentitions: covering the middle palate (M-bar) and the anterior/posterior palate (AP-bar). Four target sounds ([∫i], [t∫i], [çi], and [ki]) were evaluated under 3 recording conditions: no connector, M-bar, and AP-bar. The mean appearance ratios of correct labels (MARCs) were calculated as parameters representing speech production accuracy with the speech evaluation system. Subgroup analysis was conducted based on palate height, dental arch width, and front space volume of the oral cavity.

RESULTS

Based on the multiple linear regression test, a significant association was found between the MARCs of [∫i] with M-bar and front space (p = 0.036). In the subgroup analysis, the AP-bar had a significant effect on the MARCs of [∫i] among subjects with high palate (p = 0.026), narrow arch (p = 0.004), and small front space (p = 0.014).

CONCLUSION

RPDs with major connectors could disturb speech production among patients with high palates, narrow arches, and small front spaces.

The prosodic licensing of coda consonants in early speech: interactions with vowel length

English has a word-minimality requirement that all open-class lexical items must contain at least two moras of structure, forming a bimoraic foot (Hayes, 1995).Thus, a word with either a long vowel, or a short vowel and a coda consonant, satisfies this requirement. This raises the question of when and how young children might learn this language-specific constraint, and if they would use coda consonants earlier and more reliably after short vowels compared to long vowels. To evaluate this possibility we conducted an elicited imitation experiment with 15 two-year-old Australian English-speaking children, using both perceptual and acoustic analysis. As predicted, the children produced codas more often when preceded by short vowels. The findings suggest that English-speaking two-year-olds are sensitive to language-specific lexical constraints, and are more likely to use coda consonants when prosodically required.

Voice Onset Time for Turkish Stop Consonants in Adult Cochlear Implanted Patients

The voice onset time is a temporal acoustic parameter defined as the time between the release of the oral constriction for plosive production and the onset of vocal fold vibrations. Hearing impairment is one of the factors that can effect the magnitude of voice onset time. Since voice onset time is a useful, noninvasive method for documenting the articulatory-phonatory aspects of vocal training during speech, we investigated voice onset time values for Turkish stop consonants in adult cochlear implanted patients in order to clarify the effect of CI and sequential hearing rehabilitation over voice onset time values. The CI patients were divided into two groups according to duration of CI usage. We looked for relations between results of the study and average voice onset time values in Turkish language for adults. Mean VOT values for for both males and females in the first and second group are shown in Tables 1, 2, 3, and 4. Most syllables both in males and females statistically significant differ from average VOT values, e.g. They did not reach to normal hearing adults level. These acoustic results indicated that VOT may be an effective measure for examining the effect of cochlear implantation over the articulatory accuracy. As far as we know, this is the first publication using voice onset time values for the efficiency of cochlear implantation in adult patients. [Table: see text] [Table: see text] [Table: see text] [Table: see text].

Temporal control and compensation for perturbed voicing feedback

Previous research employing a real-time auditory perturbation paradigm has shown that talkers monitor their own speech attributes such as fundamental frequency, vowel intensity, vowel formants, and fricative noise as part of speech motor control. In the case of vowel formants or fricative noise, what was manipulated is spectral information about the filter function of the vocal tract. However, segments can be contrasted by parameters other than spectral configuration. It is possible that the feedback system monitors phonation timing in the way it does spectral information. This study examined whether talkers exhibit a compensatory behavior when manipulating information about voicing. When talkers received feedback of the cognate of the intended voicing category (saying "tipper" while hearing "dipper" or vice versa), they changed the voice onset time and in some cases the following vowel.

Auditory-motor interactions in pediatric motor speech disorders: neurocomputational modeling of disordered development

BACKGROUND/PURPOSE

Differentiating the symptom complex due to phonological-level disorders, speech delay and pediatric motor speech disorders is a controversial issue in the field of pediatric speech and language pathology. The present study investigated the developmental interaction between neurological deficits in auditory and motor processes using computational modeling with the DIVA model.

METHOD

In a series of computer simulations, we investigated the effect of a motor processing deficit alone (MPD), and the effect of a motor processing deficit in combination with an auditory processing deficit (MPD+APD) on the trajectory and endpoint of speech motor development in the DIVA model.

RESULTS

Simulation results showed that a motor programming deficit predominantly leads to deterioration on the phonological level (phonemic mappings) when auditory self-monitoring is intact, and on the systemic level (systemic mapping) if auditory self-monitoring is impaired.

CONCLUSIONS

These findings suggest a close relation between quality of auditory self-monitoring and the involvement of phonological vs. motor processes in children with pediatric motor speech disorders. It is suggested that MPD+APD might be involved in typically apraxic speech output disorders and MPD in pediatric motor speech disorders that also have a phonological component. Possibilities to verify these hypotheses using empirical data collected from human subjects are discussed.

LEARNING OUTCOMES

The reader will be able to: (1) identify the difficulties in studying disordered speech motor development; (2) describe the differences in speech motor characteristics between SSD and subtype CAS; (3) describe the different types of learning that occur in the sensory-motor system during babbling and early speech acquisition; (4) identify the neural control subsystems involved in speech production; (5) describe the potential role of auditory self-monitoring in developmental speech disorders.

Computational neural modeling of speech motor control in childhood apraxia of speech (CAS)

PURPOSE

Childhood apraxia of speech (CAS) has been associated with a wide variety of diagnostic descriptions and has been shown to involve different symptoms during successive stages of development. In the present study, the authors attempted to associate the symptoms of CAS in a particular developmental stage with particular information-processing deficits by using computational modeling with the Directions Into Velocities of Articulators (DIVA) model. The hypothesis was that the speech production system in CAS suffers from poor feed-forward control and, consequently, an increased reliance on the feedback control subsystem.

METHOD

In a series of computer simulations, the authors systematically varied the ratio between feed-forward and feedback control during production attempts in the acquisition of feed-forward motor commands. The simulations were evaluated acoustically on 4 selected key symptoms of CAS.

RESULTS

Results showed that increasing the reliance on feedback control causes increased severity of these 4 symptoms of CAS: deviant coarticulation, speech sound distortion, searching articulation, and increased variability.

CONCLUSIONS

The findings support the idea that the key symptoms found in CAS could result from an increased reliance on feedback control due to poor feed-forward commands. Two possible root causes of degraded feed-forward control in CAS are discussed: reduced somatosensory information and increased levels of neural noise.