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Purpose: This study aimed to evaluate a novel communication system designed to translate surface electromyographic (sEMG) signals from articulatory muscles into speech using a personalized, digital voice. The system was evaluated for word recognition, prosodic classification, and listener perception of synthesized speech. Method: sEMG signals were recorded from the face and neck as speakers with (n = 4) and without (n = 4) laryngectomy subvocally recited (silently mouthed) a speech corpus comprising 750 phrases (150 phrases with variable phrase-level stress). Corpus tokens were then translated into speech via personalized voice synthesis (n = 8 synthetic voices) and compared against phrases produced by each speaker when using their typical mode of communication (n = 4 natural voices, n = 4 electrolaryngeal [EL] voices). Naïve listeners (n = 12) evaluated synthetic, natural, and EL speech for acceptability and intelligibility in a visual sort-and-rate task, as well as phrasal stress discriminability via a classification mechanism. Results: Recorded sEMG signals were processed to translate sEMG muscle activity into lexical content and categorize variations in phrase-level stress, achieving a mean accuracy of 96.3% (SD = 3.10%) and 91.2% (SD = 4.46%), respectively. Synthetic speech was significantly higher in acceptability and intelligibility than EL speech, also leading to greater phrasal stress classification accuracy, whereas natural speech was rated as the most acceptable and intelligible, with the greatest phrasal stress classification accuracy. Conclusion: This proof-of-concept study establishes the feasibility of using subvocal sEMG-based alternative communication not only for lexical recognition but also for prosodic communication in healthy individuals, as well as those living with vocal impairments and residual articulatory function.

Objectives: Most cases of irresolvable hoarseness are due to deficiencies in the pliability and volume of the superficial lamina propria of the phonatory mucosa. By using a US Food and Drug Administration–approved polymer, polyethylene glycol (PEG), we created a novel hydrogel (PEG30) and investigated its effects on multiple vocal fold structural and functional parameters. Methods: We injected PEG30 unilaterally into 16 normal canine vocal folds with survival times of 1 to 4 months. High-speed videos of vocal fold vibration, induced by intratracheal airflow, and phonation threshold pressures were recorded at 4 time points per subject. Three-dimensional reconstruction analysis of 11.7 T magnetic resonance images and histologic analysis identified 3 cases wherein PEG30 injections were the most superficial, so as to maximally impact vibratory function. These cases were subjected to in-depth analyses. Results: High-speed video analysis of the 3 selected cases showed minimal to no reduction in the maximum vibratory amplitudes of vocal folds injected with PEG30 compared to the non-injected, contralateral vocal fold. All PEG30-injected vocal folds displayed mucosal wave activity with low average phonation threshold pressures. No significant inflammation was observed on microlaryngoscopic examination. Magnetic resonance imaging and histologic analyses revealed time-dependent resorption of the PEG30 hydrogel by phagocytosis with minimal tissue reaction or fibrosis. Conclusions: The PEG30 hydrogel is a promising biocompatible candidate biomaterial to restore form and function to deficient phonatory mucosa, while not mechanically impeding residual endogenous superficial lamina propria.

Purpose: This study tested the hypothesis that individuals with vocal hyperfunction would show decreases in relative fundamental frequency (RFF) surrounding a voiceless consonant. Method: This retrospective study of 2 clinical databases used speech samples from 15 control participants and women with hyperfunction-related voice disorders: 82 prior to treatment (muscle tension dysphonia, n = 22; vocal fold nodules, n = 30; vocal fold polyps, N = 30) and 18 before and after surgical removal of vocal fold nodules or polyps. Acoustic samples were analyzed with respect to the RFF at the offset and onset of voicing surrounding a voiceless consonant. Results: Individuals with vocal hyperfunction in a large clinical sample showed significant lowering of offset and onset RFF compared with controls. Voicing offset and onset RFFs were not significantly changed by the removal of vocal fold lesions in the surgical group. Conclusions: Altered offset and onset RFF in patients with hyperfunction-related voice disorders can be interpreted as a by-product of heightened levels of laryngeal muscle tension. Measurement of RFF during voice offset and onset has potential for use as a simple, noninvasive measure of vocal hyperfunction.

Purpose: The purpose of this study was to determine whether the relative fundamental frequency (RFF) surrounding a voiceless consonant in patients with hyperfunctionally related voice disorders would normalize after a successful course of voice therapy. Method: Pre- and posttherapy measurements of RFF were compared in 16 subjects undergoing voice therapy for voice disorders associated with vocal hyperfunction. Results: A 2-way analysis of variance showed a statistically significant effect of both cycle of vibration near the consonant and therapy phase (pre- vs. post-), with p less than 0.001. A post hoc paired Student's t test showed that posttherapy RFF measurements were significantly higher (more typical; p less than 0.0001) than pretherapy measurements. Conclusions: Prior to therapy, participants exhibited lowered RFF values, similar to those found previously (Stepp, Hillman, & Heaton, 2010). After successful completion of voice therapy, RFF values increased toward patterns seen previously in individuals with healthy typical voice. The goal of voice therapy in these patients was to reduce laryngeal muscle tension; therefore, the increase of RFF toward more typical values may be indicative of decreased baseline laryngeal muscle tension resulting from therapy. Results are discussed further in terms of necessary research to incorporate RFF as a clinical measure of vocal hyperfunction.

Accurate estimation of daily patterns of vocal behavior is essential to understanding the role of voice use in voice disorders. Given that clinicians currently rely on patient self-report to assess daily vocal behaviors, this study sought to assess the accuracy with which adults with and without voice disorders can estimate their amount of daily voice use in terms of phonation time. Eighteen subjects (6 patients, 6 matched members of a control group without voice disorders, 6 low voice users) wore the accelerometer-based Ambulatory Phonation Monitor (APM; model 3200, KayPENTAX, Montvale, NJ) for at least 5 workdays. Subjects were instructed to provide hourly self-reports of time spent talking using a visual analog scale. Spearman correlation coefficients and errors between self-reported and APM-based estimates of phonation time revealed subject- and group-specific characteristics. A majority of subjects exhibited a significant bias toward overestimating their phonation times, with an average absolute error of 113%. Correlation coefficients between self-reported and APM-based estimates of phonation time ranged from statistically nonsignificant to .91, reflecting large intersubject variability. Subjects in all 3 groups were moderately accurate at estimating their hourly voice use, with a consistent bias toward overestimation. The results support the potential role that ambulatory monitoring could play in improving the clinical assessment of voice disorders.

Purpose: The purpose of this study was to better understand neck intermuscular beta coherence (15-35 Hz; NIBcoh) in healthy individuals, with respect to modulation by behavioral tasks. Method: Mean NIBcoh was measured using surface electromyography at 2 anterior neck locations in 10 individuals during normal speech, static nonspeech maneuvers, \"clear\" speech (intentionally produced to maximize intelligibility), divided-attention speech, singing, and mimicked hyperfunctional speech. Results: An analysis of variance showed significant effects of both individual and condition (p = 0.001) on the mean beta-band intermuscular coherence. Dunnett's simultaneous paired t tests found decreased NIBcoh during low-attention speech, singing, and hyperfunctional speech (p[subscript adj] less than 0.05), but no significant difference in NIBcoh during nonspeech tasks or clear speech production relative to normal speech. Conclusions: Compared with normal speech, mean NIBcoh was decreased in a divided-attention speech task, but clear speech did not result in increased mean coherence relative to normal speech, possibly due to ceiling effects caused by heightened attention and precision during experimental recording. Mimicking a strained, hyperfunctional voice resulted in a reduction in mean beta intermuscular coherence quantitatively and qualitatively similar to the lowered values of mean beta coherence seen in individuals with vocal nodules relative to individuals with normal voice.

Objectives: Recently developed systems for ambulatory monitoring of voice use employ miniature accelerometers placed at the base of the anterior neck to sense phonation. As it is hoped that such systems will help improve the clinical assessment and management of voice disorders, this study was undertaken to determine the impact of dysphonia severity on the accuracy of accelerometer-based estimates of vocal function. Methods: Simultaneous recordings were made of oral acoustic (microphone) and neck skin acceleration signals for 6 normal speakers and 18 patients with voice disorders (mild to severe dysphonia) as they performed several speech tasks. Measures of phonation time, fundamental frequency, and sound pressure level were extracted from the Two types of signals and compared. Results: It was generally demonstrated that accelerometer-based measures closely approximated corresponding measurements obtained from a microphone signal across all levels of dysphonia severity. Furthermore, there was evidence that in some cases the accelerometer may actually represent a more robust approach for estimating phonation parameters in disordered voices. Conclusions: The results generally support the recent application of accelerometers as phonation sensors in ambulatory voice monitoring systems that can be used in the clinical assessment and management of voice disorders.

Adipose-derived stem cells (ASCs) may provide a clinical option for rebuilding damaged superficial lamina propria of the vocal fold. We investigated the effects of five hydrogels (hyaluronic acid [HA], collagen, fibrin, and cogels of fibrin–collagen and fibrin–HA) on the differentiation of ASCs, with the long-term goal of establishing the conditions necessary for controlling the differentiation of ASC into the functional equivalent of superficial lamina propria fibroblasts. Human ASCs were isolated and characterized by fluorescence-activated cell sorting and real-time polymerase chain reaction. According to fluorescence-activated cell sorting and gene analysis, over 90% of isolated ASCs expressed adult stem cell surface markers and expressed adult stem cell genes. Scaffold-specific gene expression and morphology were assessed by culturing the ASCs in three-dimensional hydrogels. Twofold higher amounts of total DNA were detected in fibrin and cogel cultures than in collagen and HA cultures. Elastin expression was significantly higher in cells grown in fibrin-based gels than in cells grown in other gels. Cells grown in the cogels showed elongated morphology, expressed decorin marker, and exhibited glycosaminoglycan synthesis, which indicate ASC differentiation. Our data suggest that it may be possible to control the differentiation of ASCs using scaffolds appropriate for vocal fold tissue engineering applications. In particular, cogels of HA or collagen with fibrin enhanced proliferation, differentiation, and elastin expression.

The sniffing position is traditionally considered optimal for direct laryngoscopic examination of the vocal folds. This study examined head and neck positions associated with ideal exposure of the anterior glottal commissure with a variety of laryngoscopes. A prospective investigation was done in 20 patients by comparing the force required to expose the anterior vocal folds by utilizing 3 head and neck positions with 3 different-sized tubular laryngoscopes. The completeness of anterior glottal exposure was rated and the force required to achieve this exposure was measured with a strain gauge. Three positions relating the atlanto-occipital and cervicothoracic vertebrae were analyzed: 1) extension-extension, 2) sniffing: extension-flexion, and 3) flexion-flexion. Head and neck position and laryngoscope size were both statistically significant factors for achieving complete anterior vocal fold exposure. Regardless of the laryngoscope, the number of patients in whom complete exposure could be achieved increased gradually when the position was changed from extension-extension to extension-flexion to flexion-flexion. Complete exposure was inversely related to larger laryngoscope size. According to the data herein, the flexion-flexion position provides the best glottal exposure for endotracheal intubation in those patients who are anatomically predisposed to difficulty in direct examination of the glottis. Because this places the laryngoscope lumen in a vertical position, this position is inappropriate for microlaryngoscopy. The study reinforced the concept that the sniffing position is the optimal position for microlaryngoscopy because it enables the use of the largest-lumened laryngoscope. This facilitates ideal exposure of the anterior vocal folds, which is necessary for phonomicrosurgery.

Hands-free triggering and pitch control would improve electrolarynx devices, which are inconvenient to use and sound unnatural. The present study tested the strategy of salvaging voice-related neural signals for hands-free electrolarynx control either by transferring cut recurrent laryngeal nerves (RLNs) to denervated neck strap muscles or by preserving strap muscles with their normal innervation. An RLN nerve transfer was performed at the time of total laryngectomy in 8 individuals, and in 5 of these subjects, strap muscles with intact ansa cervicalis innervation were also preserved for comparison. Neck surface electromyography performed over the strap muscles was used periodically for more than 1 year on phonatory and nonphonatory tasks. Signals were eventually obtained in all subjects from both RLN-innervated and ansa-innervated strap muscles that correlated with speech production. After 1 year, RLN-driven signals were larger than ansa-driven signals in magnitude, and their timing appeared better correlated with intended phonation. The results show that neck surface electromyography is an effective control source for hands-free electrolarynx activation, and that RLN transfer may provide the best approach for obtaining phonation-related activity.