Aerodynamic and acoustic voice measurements of patients with vocal nodules: variation in baseline and changes across voice therapy

Subject-Specific Modeling by Domain Adaptation for the Estimation of Subglottal Pressure from Neck-Surface Acceleration Signals

Subglottal air pressure is a critical physiologically-based parameter that reveals fundamental pathophysiological processes in patients with voice disorders. However, its assessment in both laboratory and ambulatory settings presents significant challenges due to the necessity for specialized instruments, invasive procedures, and the impracticality of direct measurement in ambulatory contexts. This study expands upon previous efforts to estimate subglottal pressure from portable, lightweight neck-surface acceleration signals using a physiologically relevant model of voice production combined with machine learning techniques. The proposed approach employs a neural network architecture initially trained with numerical simulations from the voice production model, which is subsequently refined through a domain adaptation strategy from synthetic data to in vivo laboratory data. This proposed method provides a means to create subject and group-specific refinements of the original neural network. For comprehensive comparisons with previous methods reported in the literature, the proposed approach is applied to both normal and disordered voices, including cases of unilateral vocal fold paralysis and phonotraumatic and non-phonotraumatic vocal hyperfunction. The study is divided into two datasets, encompassing a total of 135 participants. The in vivo recordings consist of synchronous measurements of oral airflow, intraoral pressure, and signals from a microphone and a neck-surface accelerometer. Each participant was asked to utter /p/-vowel syllable gestures with variations in loudness, vowels, pitch, and voice quality. Compared to previously reported approaches, the proposed method results in subject-specific models that achieve over a 21% improvement in the estimation of subglottal pressure, as measured by root mean square error. These findings underscore the effectiveness of a non-linear, subject-specific regression approach in enhancing the estimation of subglottal pressure from neck-surface vibration signals.

Aerodynamic Threshold Measures for Reflecting Glottal Closure in Voice Disorders

PURPOSE

Previous work suggested that phonation threshold pressure (PTP), phonation threshold flow (PTF), and phonation threshold power (PTW) could be effective aerodynamic measures for quantifying glottal incompetence. This study examined how these measures could reflect varying extent of incomplete glottal closure in individuals with voice disorders.

METHOD

Thirty individuals formally diagnosed with glottal incompetence, including 10 with hypofunctional disorders (hypo group) and 20 with hyperfunctional disorders (hyper group), and 30 individuals with normal voice (control group) participated in the study. PTP was measured indirectly by intra-oral pressure during production of bilabial stop consonant-vowel syllables, PTF was measured during the sustained vowel /a/, and PTW was obtained as the product of PTP and PTF. The extent of incomplete glottal closure was quantified by normalized glottal gap (NGG) and normalized glottal gap area (NGGA) based on image analysis of videostroboscopic recordings of sustained /i/.

RESULTS

Significant differences in all threshold measures (p < .05) were found among three participant groups with medium-to-large effect sizes (ηp2 = .128-.220), with significantly higher values for the hypo group than the control group and no significant differences between the hyper and control groups. Receiver operating characteristic (ROC) analysis showed the highest diagnostic or classification accuracy contrasting between the hypo and control groups (area under the ROC curve = .717-.757), with the highest classification accuracy for PTW. There were significant, moderate-to-strong positive correlations with NGG and NGGA for the disorders group (Pearson's r = .4244-.6226) and the hypo group (r = .5689-.8949).

CONCLUSIONS

These measures could be effective for identifying glottal incompetence, especially for hypofunctional disorders. PTW could be more sensitive than PTP and PTF in reflecting the extent of incomplete glottal closure, consistent with theoretical predictions. Their relative sensitivities for quantifying distinct incomplete glottal closures specific to different voice disorders should be evaluated in future studies.

Can Vocal Therapy With Transcutaneous Electrical Nerve Stimulation (TENS) Followed by Vocal Exercises Reduce Benign Laryngeal Lesions in Dysphonic Women?: Randomized, Blind Clinical Trial

PURPOSE

To investigate the effectiveness of vocal therapy with the use of low-frequency transcutaneous electrical nerve stimulation (TENS) followed by voice exercises on vocal fold lesion size, vocal quality and quality of life in dysphonic women.

METHODS

27 women with vocal nodules participated, randomized into to: experimental group (EG)-13 women who received vocal therapy with 12 sessions of 20 min of TENS application (pulse:200μs, frequency:10Hz, motor threshold intensity, electrodes positioned in the trapezius muscle [descending fibers and submandibular region, bilaterally]). Each TENS session was followed by 30 min of vocal exercises; and the Control Group (CG)- 14 women who received 12 sessions with 20 min of application of placebo TENS (same conditions EG, but without receiving the stimulus electric), followed by 30 min of vocal exercise. Before, immediately after and one month after vocal therapy, participants underwent vocal recording for acoustic analysis, vocal self-assessment, laryngological examination and answered voice-related quality of life (V-RQOL) protocol.

RESULTS

There was reduction in the size of vocal fold lesions only in the EG, immediately after treatment and one month after treatment. Acoustic analysis showed decreases in SPI values immediately after and one month after treatment in both groups. There was improvement in voice self-perception in both groups after treatment and one month after, but no significant difference in V-RQOL values.

CONCLUSION

TENS followed by vocal exercises produced results similar to vocal therapy without TENS regarding voice quality, self-perception and quality of life in voice. However, vocal therapy with low-frequency TENS followed by vocal exercise was effective in reducing vocal fold lesion size in dysphonic women.

Continuous-Time Model Identification of the Subglottal System

Mathematical models that accurately simulate the physiological systems of the human body serve as cornerstone instruments for advancing medical science and facilitating innovative clinical interventions. One application is the modeling of the subglottal tract and neck skin properties for its use in the ambulatory assessment of vocal function, by enabling non-invasive monitoring of glottal airflow via a neck surface accelerometer. For the technique to be effective, the development of an accurate building block model for the subglottal tract is required. Such a model is expected to utilize glottal volume velocity as the input parameter and yield neck skin acceleration as the corresponding output. In contrast to preceding efforts that employed frequency-domain methods, the present paper leverages system identification techniques to derive a parsimonious continuous-time model of the subglottal tract using time-domain data samples. Additionally, an examination of the model order is conducted through the application of various information criteria. Once a low-order model is successfully fitted, an inverse filter based on a Kalman smoother is utilized for the estimation of glottal volume velocity and related aerodynamic metrics, thereby constituting the most efficient execution of these estimates thus far. Anticipated reductions in computational time and complexity due to the lower order of the subglottal model hold particular relevance for real-time monitoring. Simultaneously, the methodology proves efficient in generating a spectrum of aerodynamic features essential for ambulatory vocal function assessment.

The Immediate Impact of Targeted Exercises on Voice Characteristics in Female Speakers With Phonotraumatic Vocal Fold Lesions

OBJECTIVE

To examine the immediate impact of 30 minutes of targeted voice exercises on measures of vocal function and lesion characteristics in female speakers with phonotraumatic vocal fold lesions (PVFLs).

STUDY DESIGN

Prospective cohort study.

METHOD

Twenty-nine (n = 29) female subjects with PVFLs completed a 30 minutes targeted voice exercise protocol and a multidimensional voice analysis was conducted immediately pre and post-exercise. Analysis included expert perceptual evaluation of connected speech and stroboscopy recordings, instrumental analysis by selected aerodynamic and acoustic parameters, and self-ratings of effort and vocal function by participants. The direction and magnitude of the change from pre- to post-exercise for each individual across parameters was assessed against a Minimal Clinically Important Difference criteria.

RESULTS

Variability was observed among participants in their response to exercise and across parameters. Multidirectional change in function was demonstrated across instrumental parameters, with observations of both improvement and decline. The most consistent change observed was a reduced PTP post-exercises for 38% of participants (n = 11), and the greatest magnitude of change was observed in aerodynamic measures of airflow and pressure, and the acoustic parameter semitone range. Variability in the direction of change across instrumental measures was observed for 24% of participants (n = 7), while consistent improved function was seen for 45% (n = 13), declined function for 17% (n = 5) and no change for 14% (n = 4). Participant's self-reported effort and function post-exercise was also multidirectional, with the greatest number reporting improvement. Comparatively little change was observed in perceptual evaluation of speech and stroboscopy recordings. Findings suggest that individuals with all lesion types, sizes and liabilities have the potential to improve vocal function immediately post-exercises according to instrumental measures, with the greatest magnitude of change observed in participants with large lesions. Although participants' characteristics did not differentiate, those with nodules or polyps tended to report improvement in function and reduced effort post-exercise, whereas those with a diagnosis of pseudocyst/s or a unilateral lesion appeared to report no change or declined function.

CONCLUSION

Change in measures of vocal function was observed in female speakers with PVFLs immediately following a 30 minutes targeted exercises protocol. Many demonstrated improvement but a high degree of variability was observed in the way speakers respond, and it is likely an individual's response is influenced by a range of factors. Self-rating scales, along with key instrumental parameters sensitive to the presence of PVFLs, may prove most useful in tracking initial change in the immediate and short-term duration in this population, and in assessing stimulability and candidacy for therapy. Further exploration is warranted of stimulability for immediate and cumulative change to achieve sustained improvement in function and efficiency across time.

Spectral and cepstral measurements in women with behavioral dysphonia

PURPOSE

To investigate whether there are differences in cepstral and spectral acoustic measures between women with behavioral dysphonia with and without laryngeal lesions and verify whether there is a correlation between such measures and the auditory-perceptual evaluation of voice quality.

METHODS

The sample comprised 78 women with behavioral dysphonia without laryngeal lesions (BDWOL) and 68 with behavioral dysphonia with laryngeal lesions (vocal nodules) (BDWL). Cepstral peak prominence (CPP), cepstral peak prominence-smoothed (CPPS), spectral decrease, and H1-H2 (difference between the amplitude of the first and second harmonics) were extracted. They were submitted to the auditory-perceptual evaluation (APE) of the grade of hoarseness (GH), roughness (RO), breathiness (BR), and strain (ST).

RESULTS

BDWL women had higher H1-H2 values and lower CPP and CPPS values than BDWOL women. More deviant voices had lower CPP and CPPS values. Breathy voices had lower CPP and CPPS values and higher H1-H2 values than rough ones. There was a weak negative correlation between CPP and RO, a moderate negative correlation with GH, and a strong negative correlation with BR. CPPS had a moderate negative correlation with GH, RO, and BR. H1-H2 had a weak positive correlation with BR. There was a weak positive correlation between spectral decrease and ST.

CONCLUSION

H1-H2, CPP, and CPPS were different between BDWOL and BDWL women. Furthermore, cepstral and spectral measures were correlated with the different APE parameters.

Auditory-Motor Function Pre- and Post-Therapy in Hyperfunctional Voice Disorders: A Case Series

OBJECTIVE/HYPOTHESIS

Behavioral voice therapy is the most common treatment for hyperfunctional voice disorders (HVDs) but has limited long-term effectiveness since the comprehensive mechanisms underlying HVDs remain unclear. Recent work has implicated disordered sensorimotor integration during speech in some speakers with HVDs and suggests that auditory processing is a key factor to consider in HVD assessment and therapy. The purpose of this case-series study was to assess whether current voice therapy approaches for HVDs resulted in improvements to auditory-motor function.

STUDY DESIGN

Longitudinal (pre-post) study.

METHOD

Pre and postvoice therapy for HVDs, 11 speakers underwent an assessment of auditory-motor function via auditory discrimination of vocal pitch, responses to unanticipated auditory perturbations, and responses to predictable auditory perturbations of vocal pitch.

RESULTS

At the post-therapy session, 10 out of 11 participants demonstrated voice therapy success (via self-reported voice problems and/or auditory-perceptual judgements of voice by a clinician) and eight of the 11 participants demonstrated improvements in at least one measure of auditory discrimination and/or auditory-motor control. Specifically, three speakers demonstrated improvements in auditory discrimination, five speakers demonstrated improved (within typical cutoffs) responses to predictable perturbations, and two speakers demonstrated improvements in both auditory discrimination and auditory-motor measures.

CONCLUSIONS

Together, these findings support that voice therapy in individuals with HVDs may impact auditory-motor control and highlight the potential benefit of systematically addressing auditory function in voice therapy and assessment for HVDs.

Examining Therapy Duration in Adults With Voice Disorders

PURPOSE

This study examined the number of voice therapy sessions and the number of weeks in treatment to achieve desired voice outcomes in adults with voice disorders. Factors that may predict therapy duration were examined, as was the percentage of patients returning to the clinic for additional voice therapy after initial discharge.

METHOD

An observational cohort design was utilized. Data from 558 patients were extracted from the University of Wisconsin-Madison Voice and Swallow Outcomes Database. Patients diagnosed with muscle tension dysphonia, vocal fold paralysis, benign vocal fold lesions, laryngospasm/irritable larynx, and presbyphonia were examined. Patient demographics, auditory-perceptual assessments, acoustics, aerodynamics, videostroboscopy ratings, self-reported scales, and medical comorbidities were collected.

RESULTS

Patients required an average of 5.32 (SD = 3.43) sessions of voice therapy before voice outcomes were sufficiently improved for discharge. Average number of sessions ranged from 4.3 for presbyphonia to 6.7 for benign vocal fold lesions. Baseline overall Grade Roughness Breathiness Asthenia and Strain rating (p < .001), Dysphonia Severity Index (p < .001), Voice Handicap Index score (p < .01), age (p = .006), and occupational voice user status (p < .001) significantly predicted the number of therapy sessions required. Overall, 14.5% of patients returned for additional voice therapy following an initial discharge from treatment.

CONCLUSIONS

Findings inform our understanding of how many sessions patients with voice disorders require to achieve desired voice outcomes. Additional research is needed to optimize the efficacy of voice treatment and determine how recurrence of dysphonia might best be prevented.

Glottal Airflow Estimation using Neck Surface Acceleration and Low-Order Kalman Smoothing

The use of non-invasive skin accelerometers placed over the extrathoracic trachea has been proposed in the literature for measuring vocal function. Glottal airflow is estimated using inverse filtering or Bayesian techniques based on a subglottal impedance-based model when utilizing these sensors. However, deviations in glottal airflow estimates can arise due to sensor positioning and model mismatch, and addressing them requires a significant computational load. In this paper, we utilize system identification techniques to obtain a low order state-space representation of the subglottal impedance-based model. We then employ the resulting low order model in a Kalman smoother to estimate the glottal airflow. Our proposed approach reduces the model order by 94% and requires only 1.5% of the computing time compared to previous Bayesian methods in the literature, while achieving slightly better accuracy when correcting for glottal airflow deviations. Additionally, our Kalman smoother approach provides a measure of uncertainty in the airflow estimate, which is valuable when measurements are taken under different conditions. With its comparable accuracy in signal estimation and reduced computational load, the proposed approach has the potential for real-time estimation of glottal airflow and its associated uncertainty in wearable voice ambulatory monitors using neck-surface acceleration.

Examining Relationships Between GRBAS Ratings and Acoustic, Aerodynamic and Patient-Reported Voice Measures in Adults With Voice Disorders

OBJECTIVE

To determine if auditory-perceptual voice ratings performed using the GRBAS scale correlate with acoustic and aerodynamic measures of voice. A secondary aim was to examine the relationship between GRBAS ratings and patient-reported quality of life scales.

METHODS

GRBAS ratings, acoustic, aerodynamic and patient-reported quality of life ratings were collected from the University of Wisconsin Madison Voice and Swallow Outcomes Database for 508 adults with voice disorders. Acoustic measures included noise to harmonic ratio, jitter%, shimmer%, highest fundamental frequency (F0) of vocal range, lowest F0 of vocal range, maximum phonation time and dysphonia severity index. Aerodynamic measures included phonation threshold pressure, subglottal pressure, mean transglottal airflow and laryngeal airway resistance. Patient-reported quality of life measures included the Vocal Handicap Index (VHI) and Glottal Function Index (GFI).

RESULTS

GRBAS ratings were significantly correlated with several acoustic and aerodynamic measures, VHI and GFI. The strongest significant correlations for acoustic measures were observed between GRBAS ratings of overall voice quality and perturbation measures (jitter% r = 0.58, shimmer% r = 0.45, noise to harmonic ratio r = 0.36, Dysphonia Severity Index r = -0.56). The strongest significant correlation for aerodynamic voice measures was observed between GRBAS ratings of breathiness and transglottal airflow (r = 0.23), subglottal pressure (r = 0.49), and phonation threshold pressure (r = 0.26). GRBAS ratings were also significantly correlated with both VHI and the GFI scales. R values were higher for the VHI, but remained largely in low range for both scales.

CONCLUSIONS

Although GRBAS ratings were significantly correlated with multiple objective voice and patient related quality of life ratings, r values were low. These findings support the need for multiple voice measures when performing voice evaluations as no single voice measure was highly correlated with voice quality as measured by the GRBAS scale.

Examining Use and Effectiveness of Teletherapy for Patients with Dysphonia

OBJECTIVE(S)/HYPOTHESIS

Virtual therapy (teletherapy) for patients with dysphonia has become ubiquitous in the COVID-19 era. However, barriers to widespread implementation are evident, including unpredictable insurance coverage attributed to limited evidence supporting this approach. In our single-institution cohort, our objective was to show strong evidence for use and effectiveness of teletherapy for patients with dysphonia.

STUDY DESIGN

Single institution, retrospective cohort study.

MATERIAL AND METHODS

This was an analysis of all patients referred for speech therapy with dysphonia as primary diagnosis from 4/1/2020 to 7/1/2021 and in whom all therapy sessions were delivered in a teletherapy format. We collated and analyzed demographics and clinical characteristics and adherence to the teletherapy program. We assessed changes in perceptual assessments and vocal capabilities (GRBAS, MPT), patient-reported outcomes (V-RQOL), and metrics of session outcomes (complexity of vocal tasks, carry-over of target voice) pre- and post-teletherapy using student's t test and chi-square test.

RESULTS

Our cohort included 234 patients (mean [SD] age 52 [20] years) residing a mean (SD) distance of 51.3 (67.1) miles from our institution. The most common referral diagnosis was muscle tension dysphonia (n = 145, 62.0% patients). Patients attended a mean (SD) of 4.2 (3.0) sessions; 68.0% (n = 159) of patients completed four or more sessions and/or were deemed appropriate for discharge from teletherapy program. Statistically significant improvements were seen in complexity and consistency of vocal tasks with consistent gains in carry-over of target voice for isolated tasks and connected speech.

CONCLUSIONS

Teletherapy is a versatile and effective approach for treatment of patients with dysphonia of varying age, geography, and diagnoses.

Variability in Voice Characteristics of Female Speakers With Phonotraumatic Vocal Fold Lesions

OBJECTIVE

To examine the variability of lesion characteristics and vocal function in female speakers with phonotraumatic vocal fold lesions (PVFLs).

STUDY DESIGN

Prospective Cohort Study METHODS: Thirty adult female speakers with PVFL who were participating in voice therapy were recruited to complete a multidimensional voice analysis at four time points across 1 month. Analysis comprised self-ratings of effort and vocal function, expert ratings of videostroboscopy and audio recordings, and instrumental evaluation by selected aerodynamic and acoustic parameters. The degree of variability across time for each individual was assessed against a minimal clinically important difference threshold.

RESULTS

A high degree of variability across time was observed for participant self-ratings of perceived effort and vocal function, and for instrumental parameters. The greatest degree of variability was observed in aerodynamic measures of airflow and pressure, and the acoustic parameter semitone range. Comparatively less variability was observed in perceptual evaluation of speech, and lesion characteristics via stroboscopy still images. Findings suggest that individuals with all PVFL types and sizes present with variability in function across time, with the greatest degree of variability in function observed in participants with large lesions and vocal fold polyps.

CONCLUSION

Variability is observed in voice characteristics of female speakers with PVFLs across 1 month despite general stability in lesion presentation, suggesting vocal function can change despite the presence of laryngeal pathology. This study highlights the need to explore individual functional and lesion responses across time to determine potential for change and improvement in both aspects when selecting treatment options.

Ambulatory Monitoring of Subglottal Pressure Estimated from Neck-Surface Vibration in Individuals with and without Voice Disorders

The aerodynamic voice assessment of subglottal air pressure can discriminate between speakers with typical voices from patients with voice disorders, with further evidence validating subglottal pressure as a clinical outcome measure. Although estimating subglottal pressure during phonation is an important component of a standard voice assessment, current methods for estimating subglottal pressure rely on non-natural speech tasks in a clinical or laboratory setting. This study reports on the validation of a method for subglottal pressure estimation in individuals with and without voice disorders that can be translated to connected speech to enable the monitoring of vocal function and behavior in real-world settings. During a laboratory calibration session, a participant-specific multiple regression model was derived to estimate subglottal pressure from a neck-surface vibration signal that can be recorded during natural speech production. The model was derived for vocally typical individuals and patients diagnosed with phonotraumatic vocal fold lesions, primary muscle tension dysphonia, and unilateral vocal fold paralysis. Estimates of subglottal pressure using the developed method exhibited significantly lower error than alternative methods in the literature, with average errors ranging from 1.13 to 2.08 cm H₂O for the participant groups. The model was then applied during activities of daily living, thus yielding ambulatory estimates of subglottal pressure for the first time in these populations. Results point to the feasibility and potential of real-time monitoring of subglottal pressure during an individual's daily life for the prevention, assessment, and treatment of voice disorders.

Clinical Utility of the Ratio of Sound Pressure Level to Subglottal Pressure in Patients Surgically Treated for Phonotraumatic Vocal Fold Lesions

PURPOSE

This study aimed to determine whether a simplified, and potentially more stable, acoustic-aerodynamic voice outcome ratio (ratio of sound pressure level [SPL] to subglottal pressure) is comparable to a traditional vocal efficiency measure (ratio of acoustic power to the product of average subglottal pressure and average phonatory airflow) in terms of the ability to detect change in vocal function following surgical removal of bilateral phonotraumatic lesions.

METHOD

Pre- and postoperative acoustic and aerodynamic measures were analyzed retrospectively from 75 female patients who underwent surgical removal of bilateral phonotraumatic lesions. A 2 × 2 repeated-measures analysis of variance was conducted for each of three acoustic-aerodynamic voice outcome ratios-traditional vocal efficiency, an SPL-based ratio with both airflow and subglottal pressure, and a simplified SPL-based ratio with subglottal pressure only-to investigate the main effects of treatment stage (pre- and postsurgery), loudness condition (comfortable and loud), and their interaction. Post hoc paired samples t tests were conducted for statistically significant interactions. The within-subject variability of the measures was assessed using the coefficient of variation.

RESULTS

Although exhibiting an expected main effect of loudness (higher values in the loud condition), the traditional vocal efficiency ratio did not exhibit a main effect of treatment. For both SPL-based ratios, there were significant main effects of treatment stage (higher values postoperatively) and loudness condition (lower values in the loud condition). Within-subject, postoperative changes in the two SPL-based ratios moderately correlated with one another. The simplified ratio of SPL to subglottal pressure (without airflow) exhibited the least within-subject variability relative to the other two acoustic-aerodynamic ratios.

CONCLUSIONS

These findings indicate that SPL-based acoustic-aerodynamic voice outcome ratios increase significantly following the surgical removal of phonotraumatic vocal fold lesions. The simplified ratio of SPL to subglottal pressure exhibits the least variability and can be easily obtained without requiring the measurement of airflow.

Impact of Vocal Effort on Respiratory and Articulatory Kinematics

PURPOSE

The goal of this study was to examine the effects of increases in vocal effort, without changing speech intensity, on respiratory and articulatory kinematics in young adults with typical voices.

METHOD

A total of 10 participants completed a reading task under three speaking conditions: baseline, mild vocal effort, and maximum vocal effort. Respiratory inductance plethysmography bands around the chest and abdomen were used to estimate lung volumes during speech, and sensor coils for electromagnetic articulography were used to transduce articulatory movements, resulting in the following outcome measures: lung volume at speech initiation (LVSI) and at speech termination (LVST), articulatory kinematic vowel space (AKVS) of two points on the tongue dorsum (body and blade), and lip aperture.

RESULTS

With increases in vocal effort, and no statistical changes in speech intensity, speakers showed: (a) no statistically significant differences in LVST, (b) statistically significant increases in LVSI, (c) no statistically significant differences in AKVS measures, and (d) statistically significant reductions in lip aperture.

CONCLUSIONS

Speakers with typical voices exhibited larger lung volumes at speech initiation during increases in vocal effort, paired with reduced lip displacements. To our knowledge, this is the first study to demonstrate evidence that articulatory kinematics are impacted by modulations in vocal effort. However, the mechanisms underlying vocal effort may differ between speakers with and without voice disorders. Thus, future work should examine the relationship between articulatory kinematics, respiratory kinematics, and laryngeal-level changes during vocal effort in speakers with and without voice disorders.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.17065457.

Kalman Filter Implementation of Subglottal Impedance-Based Inverse Filtering to Estimate Glottal Airflow during Phonation

Subglottal Impedance-Based Inverse Filtering (IBIF) allows for the continuous, non-invasive estimation of glottal airflow from a surface accelerometer placed over the anterior neck skin below the larynx. It has been shown to be advantageous for the ambulatory monitoring of vocal function, specifically in the use of high-order statistics to understand long-term vocal behavior. However, during long-term ambulatory recordings over several days, conditions may drift from the laboratory environment where the IBIF parameters were initially estimated due to sensor positioning, skin attachment, or temperature, among other factors. Observation uncertainties and model mismatch may result in significant deviations in the glottal airflow estimates; unfortunately, they are very difficult to quantify in ambulatory conditions due to a lack of a reference signal. To address this issue, we propose a Kalman filter implementation of the IBIF filter, which allows for both estimating the model uncertainty and adapting the airflow estimates to correct for signal deviations. One-way analysis of variance (ANOVA) results from laboratory experiments using the Rainbow Passage indicate an improvement using the modified Kalman filter on amplitude-based measures for phonotraumatic vocal hyperfunction (PVH) subjects compared to the standard IBIF; the latter showing a statistically difference (p-value = 0.02, F = 4.1) with respect to a reference glottal volume velocity signal estimated from a single notch filter used here as ground-truth in this work. In contrast, maximum flow declination rates from subjects with vocal phonotrauma exhibit a small but statistically difference between the ground-truth signal and the modified Kalman filter when using one-way ANOVA (p-value = 0.04, F = 3.3). Other measures did not have significant differences with either the modified Kalman filter or IBIF compared to ground-truth, with the exception of H1–H2, whose performance deteriorates for both methods. Overall, both methods (modified Kalman filter and IBIF) show similar glottal airflow measures, with the advantage of the modified Kalman filter to improve amplitude estimation. Moreover, Kalman filter deviations from the IBIF output airflow might suggest a better representation of some fine details in the ground-truth glottal airflow signal. Other applications may take more advantage from the adaptation offered by the modified Kalman filter implementation.

The influence of gravity on respiratory kinematics during phonation measured by dynamic magnetic resonance imaging

Respiratory kinematics are important for the regulation of voice production. Dynamic MRI is an excellent tool to study respiratory motion providing high-resolution cross-sectional images. Unfortunately, in clinical MRI systems images can only be acquired in a horizontal subject position, which does not take into account gravitational effects on the respiratory apparatus. To study the effect of body posture on respiratory kinematics during phonation, 8 singers were examined both in an open-configuration MRI with a rotatable gantry and a conventional horizontal MRI system. During dynamic MRI the subjects sang sustained tones at different pitches in both supine and upright body positions. Sagittal images of the respiratory system were obtained at 1-3 images per second, from which 6 anatomically defined distances were extracted to characterize its movements in the anterior, medium and posterior section of the diaphragm as well as the rip cage (diameter at the height of the 3rd and 5th rip) and the anterior-posterior position of the diaphragm cupola. Regardless of body position, singers maintained their general principles of respiratory kinematics with combined diaphragm and thorax muscle activation for breath support. This was achieved by expanding their chest an additional 20% during inspiration when singing in the supine position but not for sole breathing. The diaphragm was cranially displaced in supine position for both singing and breathing and its motion range increased. These results facilitate a more realistic extrapolation of research data obtained in a supine position.

Changes in the Daily Phonotrauma Index Following the Use of Voice Therapy as the Sole Treatment for Phonotraumatic Vocal Hyperfunction in Females

Purpose The aim of this study was to use the Daily Phonotrauma Index (DPI) to quantify group-based changes in the daily voice use of patients with phonotraumatic vocal hyperfunction (PVH) after receiving voice therapy as the sole treatment. This is part of an ongoing effort to validate an updated theoretical framework for PVH. Method A custom-designed ambulatory voice monitor was used to collect 1 week of pre- and posttreatment data from 52 female patients with PVH. Normative weeklong data were also obtained from 52 matched controls. Each week was represented by the DPI, which is a combination of neck-surface acceleration magnitude skewness and the standard deviation of the difference between the first and second harmonic magnitudes. Results Compared to pretreatment, the DPI statistically decreased towards normal in the patient group after treatment (Cohen's d = -0.25). The posttreatment patient group's DPI was still significantly higher than the control group (d = 0.68). Conclusions The DPI showed the pattern of improved ambulatory voice use in a group of patients with PVH following voice therapy that was predicted by the updated theoretical framework. Per the prediction, voice therapy was associated with a decreased potential for phonotrauma in daily voice use, but the posttreatment patient group data were still significantly different from the normative control group data. This posttreatment difference is interpreted as reflecting the impact on voice use of the persistence of phonotrauma-induced structural changes to the vocal folds. Further validation of the DPI is needed to better understand its potential clinical use.

Acoustic Variability in the Healthy Female Voice Within and Across Days: How Much and Why?

Purpose The aims of this study were (1) to quantify variability in voice production (as measured acoustically) within and across consecutive days in vocally healthy female speakers, (2) to identify which acoustic measures are sensitive to this variability, and (3) to identify participant characteristics related to such voice variability. Method Participants included 45 young women with normal voices who were stratified by age, specifically 18-23, 24-29, and 30-35 years. Following an initial acoustic and auditory-perceptual voice assessment, participants performed standardized field voice recordings 3 times daily across a 7-day period. Acoustic analyses involved 32 cepstral-, spectral-, and time-based measures of connected speech and sustained vowels. Relationships among acoustic data and select demographic, health, and lifestyle (i.e., participant-based) factors were also examined. Results Significant time-of-day effects were observed for acoustic analyses within speakers (p < .05), with voices generally being worse in the morning. No significant differences were observed across consecutive days. Variations in voice production were associated with several participant factors, including improved voice with increased voice use; self-perceived poor voice function, minimal or no alcohol consumption, and extroverted personality; and worse voice with regular or current menstruation, depression, and anxiety. Conclusions This acoustic study provides essential information regarding the nature and extent to which healthy voices vary throughout the day and week. Participant-based factors that were associated with improved voice over time included increased voice use, self-perceived poor voice function, minimal or no alcohol consumption, and extroverted personality. Factors associated with worse voice production over time included regular or current menstruation, and depression and anxiety.

Impaired auditory discrimination and auditory-motor integration in hyperfunctional voice disorders

Hyperfunctional voice disorders (HVDs) are the most common class of voice disorders, consisting of diagnoses such as vocal fold nodules and muscle tension dysphonia. These speech production disorders result in effort, fatigue, pain, and even complete loss of voice. The mechanisms underlying HVDs are largely unknown. Here, the auditory-motor control of voice fundamental frequency (f_o) was examined in 62 speakers with and 62 speakers without HVDs. Due to the high prevalence of HVDs in singers, and the known impacts of singing experience on auditory-motor function, groups were matched for singing experience. Speakers completed three tasks, yielding: (1) auditory discrimination of voice f_o; (2) reflexive responses to sudden f_o shifts; and (3) adaptive responses to sustained f_o shifts. Compared to controls, and regardless of singing experience, individuals with HVDs showed: (1) worse auditory discrimination; (2) comparable reflexive responses; and (3) a greater frequency of atypical adaptive responses. Atypical adaptive responses were associated with poorer auditory discrimination, directly implicating auditory function in this motor disorder. These findings motivate a paradigm shift for understanding development and treatment of HVDs.

Clinical Features of Essential Voice Tremor and Associations with Tremor Severity and Response to Octanoic Acid Treatment

OBJECTIVES/HYPOTHESIS

The purpose of this study was to characterize the clinical features, tremor variability, and factors related to octanoic acid (OA) treatment response in essential voice tremor (EVT).

STUDY DESIGN

Prospective, double blind, placebo-controlled, crossover study with secondary analysis.

METHODS

Clinical tremor features in 16 individuals with EVT were comprehensively assessed, and correlations with acoustic tremor severity were determined. Intrasubject and intersubject variability measures were analyzed from 18 repeated measures for each acoustic tremor variable. Clinical correlates of treatment response were evaluated, and cumulative effects over a 2-week period of OA drug dosing were assessed.

RESULTS

Participants with EVT were 90% female with a mean age of 70.31 (±8.68) years at the time of testing. Neurologist-rated body tremor beyond the vocal tract region was present in 69% of participants, and multiple vocal tract regions contributed to the voice tremor. The mean frequency of amplitude tremor was 4.67 Hz (±0.88). Respiratory tremor was evident in 50% of participants. Participants experienced moderate voice-related disability as assessed on the Voice Handicap Index-10 (19.38, ±8.50), and increased speaking effort. Acoustic tremor severity was significantly associated with severity of tremor affecting vocal tract structures. Overall intrasubject consistency was strong (single measures intraclass correlation coefficient = 0.701, P < .01), with high intersubject variability. Acoustic tremor severity was significantly, positively associated with treatment response, and results suggested a cumulative OA benefit for magnitude of amplitude tremor.

CONCLUSIONS

This study identified common clinical correlates of EVT and demonstrated positive associations between acoustic tremor severity, severity of affected vocal tract structures, and response to treatment.

LEVEL OF EVIDENCE

2 Laryngoscope, 2021.

Perceptual and Acoustic Assessment of Strain Using Synthetically Modified Voice Samples

Purpose Assessment of strained voice quality is difficult due to the weak reliability of auditory-perceptual evaluation and lack of strong acoustic correlates. This study evaluated the contributions of relative fundamental frequency (RFF) and mid-to-high frequency noise to the perception of strain. Method Stimuli were created using recordings of speakers producing /ifi/ with a comfortable voice and with maximum vocal effort. RFF values of the comfortable voice samples were synthetically lowered, and RFF values of the maximum vocal effort samples were synthetically raised. Mid-to-high frequency noise was added to the samples. Twenty listeners rated strain in a visual sort-and-rate task. The effects of RFF modification and added noise on strain were assessed using an analysis of variance; intra- and interrater reliability were compared with and without noise. Results Lowering RFF in the comfortable voice samples increased their perceived strain, whereas raising RFF in the maximum vocal effort samples decreased their strain. Adding noise increased strain and decreased intra- and interrater reliability relative to samples without added noise. Conclusions Both RFF and mid-to-high frequency noise contribute to the perception of strain. The presence of dysphonia may decrease the reliability of auditory-perceptual evaluation of strain, which supports the need for complementary objective assessments. Supplemental Material https://doi.org/10.23641/asha.13172252.

Changes in a Daily Phonotrauma Index After Laryngeal Surgery and Voice Therapy: Implications for the Role of Daily Voice Use in the Etiology and Pathophysiology of Phonotraumatic Vocal Hyperfunction

Purpose This study attempts to gain insights into the role of daily voice use in the etiology and pathophysiology of phonotraumatic vocal hyperfunction (PVH) by applying a logistic regression-based daily phonotrauma index (DPI) to predict group-based improvements in patients with PVH after laryngeal surgery and/or postsurgical voice therapy. Method A custom-designed ambulatory voice monitor was used to collect 1 week of pre- and postsurgery data from 27 female patients with PVH; 13 of these patients were also monitored after postsurgical voice therapy. Normative weeklong data were obtained from 27 matched controls. Each week was represented by the DPI, standard deviation of the difference between the first and second harmonic amplitudes (H1-H2). Results Compared to pretreatment, the DPI significantly decreased in the patient group after surgery (Cohen's d effect size = -0.86) and voice therapy (d = -1.06). The patient group DPI only normalized after voice therapy. Conclusions The DPI produced the expected pattern of improved ambulatory voice use across laryngeal surgery and postsurgical voice therapy in a group of patients with PVH. The results were interpreted as providing new objective information about the role of daily voice use in the etiology and pathophysiology of PVH. The DPI is viewed as an estimate of potential vocal fold trauma that relies on combining the long-term distributional characteristics of two parameters representing the magnitude of phonatory forces (neck-surface acceleration magnitude) and vocal fold closure dynamics (H1-H2). Further validation of the DPI is needed to better understand its potential clinical use.

An Updated Theoretical Framework for Vocal Hyperfunction

Purpose The purpose of this viewpoint article is to facilitate research on vocal hyperfunction (VH). VH is implicated in the most commonly occurring types of voice disorders, but there remains a pressing need to increase our understanding of the etiological and pathophysiological mechanisms associated with VH to improve the prevention, diagnosis, and treatment of VH-related disorders. Method A comprehensive theoretical framework for VH is proposed based on an integration of prevailing clinical views and research evidence. Results The fundamental structure of the current framework is based on a previous (simplified) version that was published over 30 years ago (Hillman et al., 1989). A central premise of the framework is that there are two primary manifestations of VH-phonotraumatic VH and nonphonotraumatic VH-and that multiple factors contribute and interact in different ways to cause and maintain these two types of VH. Key hypotheses are presented about the way different factors may contribute to phonotraumatic VH and nonphonotraumatic VH and how the associated disorders may respond to treatment. Conclusions This updated and expanded framework is meant to help guide future research, particularly the design of longitudinal studies, which can lead to a refinement in knowledge about the etiology and pathophysiology of VH-related disorders. Such new knowledge should lead to further refinements in the framework and serve as a basis for improving the prevention and evidence-based clinical management of VH.

Laryngeal strategies to minimize vocal fold contact pressure and their effect on voice production

The goal of this study is to identify laryngeal strategies that minimize vocal fold contact pressure while producing a target sound pressure level (SPL) using a three-dimensional voice production model. The results show that while the subglottal pressure and transverse stiffness can be manipulated to reduce the peak contact pressure, such manipulations also reduce the SPL, and are thus less effective in reducing contact pressure in voice tasks targeting a specific SPL level. In contrast, changes in the initial glottal angle and vocal fold vertical thickness that reduce the contact pressure also increase the SPL. Thus, in voice tasks targeting a specific SPL, such changes in the initial glottal angle and vertical thickness also lower the subglottal pressure, which further reduces the peak contact pressure. Overall the results show that for voice tasks with a target SPL level, vocal fold contact pressure can be significantly reduced by adopting a barely abducted glottal configuration or reducing the vocal fold vertical thickness. Aerodynamic measures are effective in identifying voice production with large initial glottal angles, but by themselves alone are not useful in differentiating hyperadducted vocal folds from barely abducted vocal folds, which may be better differentiated by closed quotient and voice type measures.

Estimation of Subglottal Pressure From Neck Surface Vibration in Patients With Voice Disorders

Purpose Given the established linear relationship between neck surface vibration magnitude and mean subglottal pressure (Ps) in vocally healthy speakers, the purpose of this study was to better understand the impact of the presence of a voice disorder on this baseline relationship. Method Data were obtained from participants with voice disorders representing a variety of glottal conditions, including phonotraumatic vocal hyperfunction, nonphonotraumatic vocal hyperfunction, and unilateral vocal fold paralysis. Participants were asked to repeat /p/-vowel syllable strings from loud-to-soft loudness levels in multiple vowel contexts (/pa/, /pi/, /pu/) and pitch levels (comfortable, higher than comfortable, lower than comfortable). Three statistical metrics were computed to analyze the regression line between neck surface accelerometer (ACC) signal magnitude and Ps within and across pitch, vowel, and voice disorder category: coefficient of determination (r 2), slope, and intercept. Three linear mixed-effects models were used to evaluate the impact of voice disorder category, pitch level, and vowel context on the relationship between ACC signal magnitude and Ps. Results The relationship between ACC signal magnitude and Ps was statistically different in patients with voice disorders than in vocally healthy controls; patients exhibited higher levels of Ps given similar values of ACC signal magnitude. Negligible effects were found for pitch condition within each voice disorder category, and negligible-to-small effects were found for vowel context. The mean of patient-specific r 2 values was .63, ranging from .13 to .92. Conclusions The baseline, linear relationship between ACC signal magnitude and Ps is affected by the presence of a voice disorder, with the relationship being participant-specific. Further work is needed to improve ACC-based prediction of Ps, across treatment, and during naturalistic speech production.

Effectiveness of voice therapy in patients with vocal fold nodules: a systematic search and narrative review

BACKGROUND/OBJECTIVE

An adult with vocal fold nodules can suffer from hoarseness, breathiness and vocal fatigue, which, in turn, significantly affects their vocal participation as well as activities. A well-designed voice therapy program improves the quality of life and vocal functionality. This is a narrative review with a systematic search of the current literature about the effectiveness of voice therapy interventions in adults with vocal fold nodules.

METHODS

Several key terms were used for the database electronic search of articles. Strict inclusion criteria were used and a broad evaluation of the studies was performed. This included the level of evidence based on the National Health and Medical Research Council levels of evidence, assessment, and critical appraisal.

RESULTS

Nine out of 30 reviewed articles met the criteria of inclusion and reported positive effects of voice therapy intervention on adult patients with vocal fold nodules. The vast majority of the reviewed studies reported multidimensional voice measures outcome data, most of them containing visual-perceptual, auditory-perceptual, acoustic and self-assessment results. Regardless of receiving direct or indirect or a combination of both voice therapy contents, nearly all voice quality parameters were found to improve after treatment. Short-term treatment (< 3 weeks) may be as beneficial as longer traditional voice therapy programs, and using telepractice voice therapy may be an achievable and practical way of delivering treatment and enhance adherence to therapy. The study design and the evidence levels of the included studies were low (≤ III-2) and the risk of bias of the comparative studies was moderate.

CONCLUSION

This narrative review cannot conclude the general effectiveness of voice therapy programs. Further research and understanding of what specific parameters (exercise and techniques) of a therapy's content will improve voice outcome measures. More studies are required to investigate whether or not voice therapy benefits are sustainable 6 months after ending the therapy. However, improved evidence is required to suggest that short period treatments are as beneficial as traditional therapy programs. Telepractice voice therapy may be an achievable and practical way of delivering treatment and enhance adherence to therapy.

Relevant Work Factors Associated with Voice Disorders in Early Childhood Teachers: A Comparison between Kindergarten and Elementary School Teachers in Yancheng, China

Background: Early childhood teachers consist of kindergarten and elementary school teachers in the lower grades. Young children at school may increase the vocal load of these teachers. Therefore, the objectives of this study were to determine the prevalence of voice disorders and the associated factors in early childhood teachers, and to determine if differences exist between kindergarten and elementary school teachers. Method: A cross-sectional survey was performed in July 2019 as a network questionnaire. Through cluster sampling, teachers (n = 414) from all five public kindergartens (n = 211) in the urban area of Yancheng, China, and four public elementary schools (n = 203) in the same school district participated in this study. Multivariate logistic regression models were used to analyze the associations among the prevalence of voice disorders in the teachers, school type, and relevant factors. Results: Our results indicated, based on the Voice Handicap Index scale (VHI-10, China), that the prevalence of voice disorders in early childhood teachers was 59.7%, while that in elementary school teachers (65.5%) was significantly higher than that in kindergarten teachers (54.0%) during the previous semester. Contributing factors included daily class hours, classroom air humidity, and speaking loudly during teaching. Additionally, certain types of voice usage in teaching such as falsetto speak, speaking more than other teachers, not using vocal techniques, and habitual voice clearing, were significantly associated with voice disorders. Conclusion: Most early childhood teachers have voice disorders. Compared with the kindergarten teachers, the elementary school teachers experienced a significantly higher prevalence of voice disorders. Several factors among work organization, work environment, and types of voice usage in teaching were associated with the voice disorders in early childhood teachers. The finding suggests that voice training should be provided for early childhood teachers, classroom teaching time should be decreased, and the number of teachers in basic subjects should be increased in the lower grades of elementary schools.

Is there an improvement on acoustic voice parameters in patients with bilateral vocal fold nodules after voice therapy? a meta-analysis

BACKGROUND/OBJECTIVE

The aim of this study is to estimate the effect of voice therapy intervention in adults with vocal fold nodules, on three acoustic voice parameters (fundamental frequency_, jitter and shimmer). The purpose of this meta-analysis is to present evidence based on literature regarding objective acoustic voice parameters changes, after voice therapy, in patients with bilateral VFNs. A pooled statistical analysis comparing pre- and post-therapy measurements of three acoustic voice parameters (average F0, % jitter and % shimmer) were performed.

METHODS

A literature review was performed by searching studies in adults, with bilateral vocal fold nodules who received voice therapy, and where voice quality was evaluated quantitatively using acoustic analysis, before and after treatment. Meta-analysis was performed using random-effects model. PubMed, CINAHL, CENTRAL and Web of Science were searched for retrospective and prospective cohort, cross-sectional and case-control with comparative studies in adults published between January/1995 and March/2019 and English written. Search terms used were: intervention, therapy, vocal, voice, nodules, bilateral, multidimensional assessment, acoustic and analysis.

RESULTS

Overall 1950 articles were identified. After removing repeated articles and conducting screening stages using inclusion and exclusion criteria, a total of four studies were selected with 147 participants for the meta-analysis. The pooled results analysis showed a statistically significant effect in two acoustic parameters after voice therapy: (1) F0 [increased mean difference post-therapy was 33.00 Hz (95% CI 20.26-45.74, p < 0.001)] and (2) jitter (%) [decreased mean difference post-therapy was 0.59% (95% CI 0.23-0.94%, p = 0.001)]. In addition, a non-statistically significant effect in shimmer (%) [decreased mean difference post-therapy was 2.98% (95% CI - 0.03-6.00, p = 0.052)].

CONCLUSION

Acoustic analysis has a clinical role in patients with vocal fold nodules, by objectively assessing and providing data on the effect of voice therapy in voice acoustic parameters. This meta-analysis has shown that patients with vocal fold nodules improved their acoustic voice parameters after receiving voice therapy.

Differences in Weeklong Ambulatory Vocal Behavior Between Female Patients With Phonotraumatic Lesions and Matched Controls

Purpose Previous work using ambulatory voice recordings has shown no differences in average vocal behavior between patients with phonotraumatic vocal hyperfunction and matched controls. This study used larger groups to replicate these results and expanded the analysis to include distributional characteristics of ambulatory voice use and measures indicative of glottal closure. Method Subjects included 180 adult women: 90 diagnosed with vocal fold nodules or polyps and 90 age-, sex-, and occupation-matched controls with no history of voice disorders. Weeklong summary statistics (average, variability, skewness, kurtosis) of voice use were computed from neck-surface acceleration recorded using an ambulatory voice monitor. Voice measures included estimates of sound pressure level (SPL), fundamental frequency (f _o), cepstral peak prominence, and the difference between the first and second harmonic magnitudes (H1-H2). Results Statistical comparisons resulted in medium-large differences (Cohen's d ≥ 0.5) between groups for SPL skewness, f _o variability, and H1-H2 variability. Two logistic regressions (theory-based and stepwise) found SPL skewness and H1-H2 variability to classify patients and controls based on their weekly voice data, with an area under the receiver operating characteristic curve of 0.85 and 0.82 on training and test sets, respectively. Conclusion Compared to controls, the weekly voice use of patients with phonotraumatic vocal hyperfunction reflected higher SPL tendencies (negatively skewed SPL) with more abrupt glottal closure (reduced H1-H2 variability, especially toward higher values). Further work could examine posttreatment data (e.g., after surgery and/or therapy) to determine the extent to which these differences are associated with the etiology and pathophysiology of phonotraumatic vocal fold lesions.

Improved subglottal pressure estimation from neck-surface vibration in healthy speakers producing non-modal phonation

Subglottal air pressure plays a major role in voice production and is a primary factor in controlling voice onset, offset, sound pressure level, glottal airflow, vocal fold collision pressures, and variations in fundamental frequency. Previous work has shown promise for the estimation of subglottal pressure from an unobtrusive miniature accelerometer sensor attached to the anterior base of the neck during typical modal voice production across multiple pitch and vowel contexts. This study expands on that work to incorporate additional accelerometer-based measures of vocal function to compensate for non-modal phonation characteristics and achieve an improved estimation of subglottal pressure. Subjects with normal voices repeated /p/-vowel syllable strings from loud-to-soft levels in multiple vowel contexts (/ɑ/, /i/, and /u/), pitch conditions (comfortable, lower than comfortable, higher than comfortable), and voice quality types (modal, breathy, strained, and rough). Subject-specific, stepwise regression models were constructed using root-mean-square (RMS) values of the accelerometer signal alone (baseline condition) and in combination with cepstral peak prominence, fundamental frequency, and glottal airflow measures derived using subglottal impedance-based inverse filtering. Five-fold cross-validation assessed the robustness of model performance using the root-mean-square error metric for each regression model. Each cross-validation fold exhibited up to a 25% decrease in prediction error when the model incorporated multidimensional aspects of the accelerometer signal compared with RMS-only models. Improved estimation of subglottal pressure for non-modal phonation was thus achievable, lending to future studies of subglottal pressure estimation in patients with voice disorders and in ambulatory voice recordings.

Impact of Remnant Nodules on Immediate and Long-term Outcomes of Voice Therapy for Vocal Fold Nodules

OBJECTIVES

In this study, we aimed to assess whether remnant vocal fold nodules (VFN) influence immediate and long-term voice outcomes after voice therapy.

STUDY DESIGN

This is a retrospective cohort study evaluating immediate and long-term voice outcomes.

METHODS

Twenty-five adult patients with VFN who completed voice therapy were included in this study. Patients were classified into remnant (n = 18) and nonremnant (n = 7) groups according to the presence of remnant nodules immediately after completion of voice therapy. Acoustic and perceptual parameters, as well as voice handicap index (VHI), were compared between groups immediately (immediate outcome) and more than 3 months (long-term outcome) after completion of voice therapy.

RESULTS

Immediately after voice therapy, there were no significant differences between groups in grade-roughness-breathiness-asthenia-strain (GRBAS) score, jitter, shimmer, noise-to-harmonics ratio, voice range profile, or s/z ratio. Postvoice therapy VHI scores did not significantly differ between the two groups (9.29 ± 8.94 in the nonremnant group vs. 12.78 ± 9.01 in the remnant group, P = 0.392). The overall GRBAS grade of all patients was maintained at 0 or 1 during long-term follow-up. There was no significant difference between the long-term VHI scores of the remnant group (10.00 ± 8.58) and the nonremnant group (5.67 ± 8.71) (P = 0.306).

CONCLUSIONS

Immediately after voice therapy, perceptual scores, acoustic parameters, and VHI scores all significantly improved regardless of presence of remnant nodules. Favorable outcomes of voice therapy were maintained during long-term follow-up regardless of presence of remnant nodules after voice therapy.

Impact of Nonmodal Phonation on Estimates of Subglottal Pressure From Neck-Surface Acceleration in Healthy Speakers

Purpose The purpose of this study was to evaluate the effects of nonmodal phonation on estimates of subglottal pressure (Ps) derived from the magnitude of a neck-surface accelerometer (ACC) signal and to confirm previous findings regarding the impact of vowel contexts and pitch levels in a larger cohort of participants. Method Twenty-six vocally healthy participants (18 women, 8 men) were asked to produce a series of p-vowel syllables with descending loudness in 3 vowel contexts (/a/, /i/, and /u/), 3 pitch levels (comfortable, high, and low), and 4 elicited phonatory conditions (modal, breathy, strained, and rough). Estimates of Ps for each vowel segment were obtained by averaging the intraoral air pressure plateau before and after each segment. The root-mean-square magnitude of the neck-surface ACC signal was computed for each vowel segment. Three linear mixed-effects models were used to statistically assess the effects of vowel, pitch, and phonatory condition on the linear relationship (slope and intercept) between Ps and ACC signal magnitude. Results Results demonstrated statistically significant linear relationships between ACC signal magnitude and Ps within participants but with increased intercepts for the nonmodal phonatory conditions; slopes were affected to a lesser extent. Vowel and pitch contexts did not significantly affect the linear relationship between ACC signal magnitude and Ps. Conclusion The classic linear relationship between ACC signal magnitude and Ps is significantly affected when nonmodal phonation is produced by a speaker. Future work is warranted to further characterize nonmodal phonatory characteristics to improve the ACC-based prediction of Ps during naturalistic speech production.

Indirect vs Direct Voice Therapy for Children With Vocal Nodules: A Randomized Clinical Trial

Importance

Benign vocal fold nodules affect 12% to 22% of the pediatric population, and 95% of otolaryngologists recommend voice therapy as treatment. However, no randomized clinical trials that we are aware of have shown its benefits.

Objective

To determine the impact of voice therapy in children with vocal fold nodules according to pretherapy and posttherapy scores on the Pediatric Voice-Related Quality of Life (PVRQOL) survey; secondary objectives included changes in phonatory parameters.

Design, Setting, and Participants

For this multicenter randomized clinical trial, 114 children ages 6 to 10 years with vocal fold nodules, PVRQOL scores less than 87.5, and dysphonia for longer than 12 weeks were recruited from outpatient voice and speech clinics. This age range was identified because these patients have not experienced pubertal changes of the larynx, tolerate stroboscopy, and cooperate with voice therapy. Participants were blinded to treatment arm.

Interventions

Participants received either indirect or direct therapy for 8 to 12 weeks. Indirect therapy focused on education and discussion of voice principles, while direct treatment used the stimulus, response, antecedent paradigm.

Main Outcomes and Measures

The primary outcome measure was PVRQOL score change before and after treatment. Secondary phonatory measures were also compared.

Results

Overall, 114 children were recruited for study (mean [SD] age, 8 [1.4] years; 83 males [73%]); with 57 randomized to receive either indirect or direct therapy. Both direct and indirect therapy approaches showed significant differences in PVRQOL scores pretherapy to posttherapy. The mean increase in PVRQOL score for direct therapy was 19.2, and 14.7 for indirect therapy (difference, 4.5; 95.3% CI, -10.8 to 19.8). Of 44 participants in the direct therapy group, 27 (61%) achieved a clinically meaningful PVRQOL improvement, compared with 26 of 49 (53%) for indirect therapy (difference, 8%; 95% CI, -12 to 28). Post hoc stratification showed robust effects in the direct therapy group for older children (Cohen d = 0.50) and the latter two-thirds of participants (Cohen d = 0.46). Vocal fold nodules reduced in size in 31% (22 of 70) and completely resolved in 11% (8 of 70) of participants who consented to a second set of images after going through the recruitment process.

Conclusions and Relevance

Both direct and indirect voice therapy improved voice-related quality of life in children with vocal fold nodules, although there was no significant difference between approaches. Future studies may focus upon which voice therapy approaches are effective in treating age-defined populations.

Trial Registration

clinicaltrials.gov Identifier: NCT01255735.

Vocal nodules management

Vocal fold nodules present the voice clinic team with a number of clinical dilemmas which are not as simple as previously thought. The definition, aetiology, prevalence and diagnosis are all poorly understood. Furthermore, treatment evidence for both behavioural and surgical approaches is weak. This paper reviews the published evidence pertaining to all of these aspects. Specific areas of uncertainty that remain include poorly defined nomenclature, the natural history of paediatric vocal nodules, the establishment of criteria to measure successful treatment, optimal configuration of speech therapy regimens and the rationale for surgical intervention. The authors suggest the development of evidence-based guidelines for UK practice.

The Relationship Between Physiological Mechanisms and the Self-Perception of Vocal Effort

Purpose This study aimed to examine the relationship between a large set of hypothesized physiological measures of vocal effort and self-ratings of vocal effort. Method Twenty-six healthy adults modulated speech rate and vocal effort during repetitions of the utterance /ifi/, followed by self-perceptual ratings of vocal effort on a visual analog scale. Physiological measures included (a) intrinsic laryngeal tension via kinematic stiffness ratios determined from high-speed laryngoscopy, (b) extrinsic suprahyoid and infrahyoid laryngeal tension via normalized percent activations and durations derived from surface electromyography, (c) supraglottal compression via expert visual-perceptual ratings, and (d) subglottal pressure via magnitude of neck surface vibrations from an accelerometer signal. Results Individual statistical models revealed that all of the physiological predictors, except for kinematic stiffness ratios, were significantly predictive of self-ratings of vocal effort. However, a combined regression model analysis yielded only 3 significant predictors: subglottal pressure, mediolateral supraglottal compression, and the normalized percent activation of the suprahyoid muscles (adjusted R 2 = .60). Conclusions Vocal effort manifests as increases in specific laryngeal physiological measures. Further work is needed to examine these measures in combination with other contributing factors, as well as in speakers with dysphonia.

Effects of a simulated system of straw phonation on the complete phonatory range of excised canine larynges

PURPOSE

This study investigated the effects of straw phonation therapy on the aerodynamic and acoustic parameters of the vocal folds at different levels of elongation and subglottal pressure.

METHODS

20 excised canine larynges were used in both experimental (straw phonation therapy simulation) and control conditions. Aerodynamic parameters, including phonation threshold pressure (PTP), phonation instability pressure (PIP), phonation pressure range (PPR), phonation threshold flow (PTF), phonation instability flow (PIF), phonation flow range (PFR), were obtained at different levels of vocal fold elongation (0%, 10%, 20%). Acoustic parameters, including fundamental frequency (F0), jitter, shimmer, signal noise ratio (SNR) were detected at different levels of vocal fold elongation (0%, 10%, 20%) and subglottal pressure (15 cmH₂O, 20 cmH₂O, 25 cmH₂O).

RESULTS

Significant decreases in PTP and PTF and significant increases in PIP, PIF, PPR, and PFR occurred in experimental condition at all levels of elongation when compared with control condition. However, no significant changes of acoustic parameters were obtained between conditions at all levels.

CONCLUSION

At different levels of vocal fold elongation, straw phonation not only lowered the onset of normal voice, but also elevated the onset of chaotic voice, indicating a better voice economy and voice control. Moreover, the improved phonatory range demonstrated that straw phonation had the potential to prevent voice users who have high voice demand from voice fatigue and vocal damage.

The relationship between acoustical and perceptual measures of vocal effort

Excessive vocal effort is a common clinical voice symptom, yet the acoustical manifestation of vocal effort and how that is perceived by speakers and listeners has not been fully elucidated. Here, 26 vocally healthy adults increased vocal effort during the production of the utterance /ifi/, followed by self-ratings of effort on a 100 mm visual analog scale. Twenty inexperienced listeners assessed the speakers' vocal effort using the visual sort-and-rate method. Previously proposed acoustical correlates of vocal effort were calculated, including: mean sound pressure level (SPL), mean fundamental frequency (f o), relative fundamental frequency (RFF) offset cycle 10 and onset cycle 1, harmonics-to-noise ratio (HNR), cepstral peak prominence and its standard deviation (SD), and low-to-high (L/H) spectral ratio and its SD. Two separate mixed-effects regression models yielded mean SPL, L/H ratio, and HNR as significant predictors of both speaker and listener ratings of vocal effort. RFF offset cycle 10 and mean f o were significant predictors of listener ratings only. Therefore, speakers and listeners attended to similar acoustical cues when making judgments of vocal effort, but listeners also used additional time-based information. Further work is needed to determine how vocal effort manifests in the speech signal in speakers with voice disorders.

The Effects of Size and Type of Vocal Fold Polyp on Some Acoustic Voice Parameters

BACKGROUND

Vocal abuse and misuse would result in vocal fold polyp. Certain features define the extent of vocal folds polyp effects on voice acoustic parameters. The present study aimed to define the effects of polyp size on acoustic voice parameters, and compare these parameters in hemorrhagic and non-hemorrhagic polyps.

METHODS

In the present retrospective study, 28 individuals with hemorrhagic or non-hemorrhagic polyps of the true vocal folds were recruited to investigate acoustic voice parameters of vowel/ æ/ computed by the Praat software. The data were analyzed using the SPSS software, version 17.0. According to the type and size of polyps, mean acoustic differences and correlations were analyzed by the statistical t test and Pearson correlation test, respectively; with significance level below 0.05.

RESULTS

The results indicated that jitter and the harmonics-to-noise ratio had a significant positive and negative correlation with the polyp size (P=0.01), respectively. In addition, both mentioned parameters were significantly different between the two types of the investigated polyps.

CONCLUSION

Both the type and size of polyps have effects on acoustic voice characteristics. In the present study, a novel method to measure polyp size was introduced. Further confirmation of this method as a tool to compare polyp sizes requires additional investigations.

The Importance of The Occupational Vocal Load for The Occurence and Treatment of Organic Voice Disorders

Introduction

The voice represents a basic working tool for carrying out certain occupations. Hoarseness, as a consequence of vocal fold lesions, presents an important cause of work-related absences for voice professionals.

Methods

Our study was designed as a retrospective cohort one. Data on gender, workplace, vocal load and exposure to risk factors for voice disorders of the patients who had surgery in the 2014-2015 period at the tertiary centre due to benign vocal fold lesions were collected from their clinical records. We compared professional voice users (PVU) to subjects with no vocal load at work (NPVU). The SPSS programme, version 22.0, was used for statistical analysis.

Results

From 2014 to 2015, 103 PVU and 132 NPVU were surgically treated for benign vocal fold lesions. In comparison to the second group, loud speech use was reported significantly more often by PVU (40.8% vs. 14.4%), as was a fast speaking rate (22.3% vs. 9.8%) and additional vocal load outside of the workplace (23.3% vs. 12.9%). The time that had passed between the occurrence of the hoarseness and the surgical treatment did not differ between the groups. The majority of patients were satisfied with the outcome of the operation.

Conclusions

Nearly a half of the operated patients had a considerable vocal load at work. An ENT assessment prior to starting a job as well as priority phoniatric treatment of voice disorders for PVU would significantly reduce the costs of work absences and contribute to a speedier recovery and return to the workplace.

The importance of the occupational vocal load for the occurence and treatment of organic voice disorders

Introduction

The voice represents a basic working tool for carrying out certain occupations. Hoarseness, as a consequence of vocal fold lesions, presents an important cause of work-related absences for voice professionals.

Methods

Our study was designed as a retrospective cohort one. Data on gender, workplace, vocal load and exposure to risk factors for voice disorders of the patients who had surgery in the 2014-2015 period at the tertiary centre due to benign vocal fold lesions were collected from their clinical records. We compared professional voice users (PVU) to subjects with no vocal load at work (NPVU). The SPSS programme, version 22.0, was used for statistical analysis.

Results

From 2014 to 2015, 103 PVU and 132 NPVU were surgically treated for benign vocal fold lesions. In comparison to the second group, loud speech use was reported significantly more often by PVU (40.8% vs. 14.4%), as was a fast speaking rate (22.3% vs. 9.8%) and additional vocal load outside of the workplace (23.3% vs. 12.9%). The time that had passed between the occurrence of the hoarseness and the surgical treatment did not differ between the groups. The majority of patients were satisfied with the outcome of the operation.

Conclusions

Nearly a half of the operated patients had a considerable vocal load at work. An ENT assessment prior to starting a job as well as priority phoniatric treatment of voice disorders for PVU would significantly reduce the costs of work absences and contribute to a speedier recovery and return to the workplace.

Magnitude of Neck-Surface Vibration as an Estimate of Subglottal Pressure During Modulations of Vocal Effort and Intensity in Healthy Speakers

PURPOSE

This study examined the relationship between the magnitude of neck-surface vibration (NSVMag; transduced with an accelerometer) and intraoral estimates of subglottal pressure (P'sg) during variations in vocal effort at 3 intensity levels.

METHOD

Twelve vocally healthy adults produced strings of /pɑ/ syllables in 3 vocal intensity conditions, while increasing vocal effort during each condition. Measures were made of P'sg (estimated during stop-consonant closure), NSVMag (measured during the following vowel), sound pressure level, and respiratory kinematics. Mixed linear regression was used to analyze the relationship between NSVMag and P'sg with respect to total lung volume excursion, levels of lung volume initiation and termination, airflow, laryngeal resistance, and vocal efficiency across intensity conditions.

RESULTS

NSVMag was significantly related to P'sg (p < .001), and there was a significant, although small, interaction between NSVMag and intensity condition. Total lung excursion was the only additional variable contributing to predicting the NSVMag-P'sg relationship.

CONCLUSIONS

NSVMag closely reflects P'sg during variations of vocal effort; however, the relationship changes across different intensities in some individuals. Future research should explore additional NSV-based measures (e.g., glottal airflow features) to improve estimation accuracy during voice production.

Modeling the Pathophysiology of Phonotraumatic Vocal Hyperfunction With a Triangular Glottal Model of the Vocal Folds

PURPOSE

Our goal was to test prevailing assumptions about the underlying biomechanical and aeroacoustic mechanisms associated with phonotraumatic lesions of the vocal folds using a numerical lumped-element model of voice production.

METHOD

A numerical model with a triangular glottis, posterior glottal opening, and arytenoid posturing is proposed. Normal voice is altered by introducing various prephonatory configurations. Potential compensatory mechanisms (increased subglottal pressure, muscle activation, and supraglottal constriction) are adjusted to restore an acoustic target output through a control loop that mimics a simplified version of auditory feedback.

RESULTS

The degree of incomplete glottal closure in both the membranous and posterior portions of the folds consistently leads to a reduction in sound pressure level, fundamental frequency, harmonic richness, and harmonics-to-noise ratio. The compensatory mechanisms lead to significantly increased vocal-fold collision forces, maximum flow-declination rate, and amplitude of unsteady flow, without significantly altering the acoustic output.

CONCLUSION

Modeling provided potentially important insights into the pathophysiology of phonotraumatic vocal hyperfunction by demonstrating that compensatory mechanisms can counteract deterioration in the voice acoustic signal due to incomplete glottal closure, but this also leads to high vocal-fold collision forces (reflected in aerodynamic measures), which significantly increases the risk of developing phonotrauma.

Measuring vocal motor skill with a virtual voice-controlled slingshot

Successful voice training (e.g., singing lessons) and vocal rehabilitation (e.g., therapy for a voice disorder) involve learning complex, vocal behaviors. However, there are no metrics describing how humans learn new vocal skills or predicting how long the improved behavior will persist post-therapy. To develop measures capable of describing and predicting vocal motor learning, a theory-based paradigm from limb motor control inspired the development of a virtual task where subjects throw projectiles at a target via modifications in vocal pitch and loudness. Ten subjects with healthy voices practiced this complex vocal task for five days. The many-to-one mapping between the execution variables pitch and loudness and resulting target error was evaluated using an analysis that quantified distributional properties of variability: Tolerance, noise, covariation costs (TNC costs). Lag-1 autocorrelation (AC1) and detrended-fluctuation-analysis scaling index (SCI) analyzed temporal aspects of variability. Vocal data replicated limb-based findings: TNC costs were positively correlated with error; AC1 and SCI were modulated in relation to the task's solution manifold. The data suggests that vocal and limb motor learning are similar in how the learner navigates the solution space. Future work calls for investigating the game's potential to improve voice disorder diagnosis and treatment.