Differences in Daily Voice Use Measures Between Female Patients With Nonphonotraumatic Vocal Hyperfunction and Matched Controls

Effect of Smoking on Cepstral Parameters

Smoking exerts certain damage to the voice, which affects sound characteristics. This study explored the effects of smoking, smoking time, and smoking amount on cepstral parameters. We collected the acoustic signals of sustained vowels in 301 participants (135 smokers and 166 nonsmokers). The cepstral parameters, including cepstral peak prominence (CPP), CPP standard deviation (CPP SD), low to high-frequency spectral ratio (L/H), low to high-frequency spectral ratio standard deviation (L/H SD), and voice disorder cepstral/spectral index of dysphonia (CSID), of the sustained vowels were investigated through the analysis of dysphonia in speech and voice (ADSV) application. The effects of smoking on these parameters were explored. The influences of smoking time and smoking amount on cepstral parameters were also analyzed by multiple linear regression. The CPP and L/H values in the smoking group were lower than those in the nonsmoking group (CPP: P < 0.001, L/H: P = 0.033) and negatively correlated with smoking time (CPP: R2 = 0.3828, P < 0.0001; L/H: R2 = 0.02996, P = 0.0447) and smoking amount (CPP: R2 < 0.4526, P < 0.0001; L/H: R2 = 0.08823, P = 0.00005). The CPP SD, L/H SD, and CSID values in the smoking group were higher than those in the nonsmoking group (CPP SD: P = 0.006, L/H SD: P = 0.034, CSID: P < 0.001) and positively correlated with smoking time (CPP SD: R2 = 0.03648, P = 0.0265, L/H SD: R2 = 0.09121, P = 0.0004, CSID: R2 = 0.01247, P = 0.1972) and smoking amount (CPP SD: R2 = 0.05495, P = 0.0062, L/H SD: R2 = 0.1316, P < 0.0001, CSID: R2 = 0.03851, P = 0.0225). Compared with other cepstral parameters, smoking time and smoking volume had the greatest impact on CPP (smoking time: R2 = 0.385, smoking amount: R2 = 0.443). This study confirmed that smoking has a significant effect on cepstral parameters. Compared with the cepstral parameters of nonsmokers, an increase in smoking time and smoking volume increases the abnormality of the cepstral parameters of smokers.

Acoustic and Physiologic Correlates of Vocal Effort in Individuals With and Without Primary Muscle Tension Dysphonia

OBJECTIVES

The aims of this study were to determine relationships between vocal effort and (a) acoustic correlates of vocal output and (b) supraglottic compression in individuals with primary muscle tension dysphonia (pMTD) and without voice disorders (controls) in the context of a vocal load challenge.

METHOD

Twenty-six individuals with pMTD and 35 vocally healthy controls participated in a 30-min vocal load challenge. The pre- and postload relationships among self-ratings of vocal effort, various acoustic voice measures, and supraglottic compression (mediolateral and anteroposterior) were tested with multiple regression models and post hoc Pearson's correlations. Acoustic measures included cepstral peak prominence (CPP), low-to-high spectral ratio, difference in intensity between the first two harmonics, fundamental frequency, and sound pressure level (dB SPL).

RESULTS

Regression models for CPP and mediolateral compression were statistically significant. Vocal effort, diagnosis of pMTD, and vocal demand were each significant variables influencing CPP measures. CPP was lower in the pMTD group across stages. There was no statistical change in CPP following the vocal load challenge within either group, but both groups had an increase in vocal effort postload. Vocal effort and diagnosis influenced the mediolateral compression model. Mediolateral compression was higher in the pMTD group across stages and had a negative relationship with vocal effort, but it did not differ after vocal loading.

CONCLUSIONS

CPP and mediolateral supraglottic compression were influenced by vocal effort and diagnosis of pMTD. Increased vocal effort was associated with lower CPP, particularly after vocal load, and decreased mediolateral supraglottic compression in the pMTD group.

Detecting Mild Phonotrauma in Daily Life

OBJECTIVE

The aim of this study was to gain quantitative insights into the role of daily voice use associated with mild phonotrauma via the Daily Phonotrauma Index (DPI), a measure derived from neck-surface acceleration magnitude (NSAM) and difference between the first two harmonic magnitudes (H1 - H2).

METHODS

An ambulatory voice monitor recorded weeklong voice use for 151 female patients with phonotraumatic vocal hyperfunction (PVH) and 181 female vocally healthy controls. Three laryngologists rated phonotrauma severity from each patient's laryngoscopy. Mixed generalized linear models evaluated the accuracy, sensitivity, and specificity of the original DPI trained on all patients versus a mild DPI version trained on only patients rated with mild phonotrauma. Individual contribution of NSAM and H1 - H2 to each DPI model was also evaluated.

RESULTS

Reliability across the laryngologists' phonotrauma ratings was moderate (Fleiss κ = 0.41). There were 70, 69, and 12 patients with mild, moderate, and severe phonotrauma, respectively. The mild DPI, compared to the original DPI, correctly classified more patients with mild phonotrauma (Cohen's d = 0.9) and less controls (d = -0.9) and did not change in overall accuracy. H1 - H2 contributed less to mild phonotrauma classification than NSAM for mild DPI.

CONCLUSIONS

Compared with the original DPI, the mild DPI exhibited higher sensitivity to mild phonotrauma and lower specificity to controls, but the same overall classification accuracy. These results support the mild DPI as a promising detector of early phonotrauma and that NSAM may be associated with early phonotrauma, and H1 - H2 may be a biomarker associated with vocal fold vibration in the presence of lesions.

LEVEL OF EVIDENCE

Level 4, case-control study Laryngoscope, 133:3094-3099, 2023.

Modeling the influence of the extrinsic musculature on phonation

Neck muscles play important roles in various physiological tasks, including swallowing, head stabilization, and phonation. The mechanisms by which neck muscles influence phonation are not well understood, with conflicting reports on the change in fundamental frequency for ostensibly the same neck muscle activation scenarios. In this work, we introduce a reduced-order muscle-controlled vocal fold model, comprising both intrinsic muscle control and extrinsic muscle effects. The model predicts that when the neck muscles pull the thyroid cartilage in the superior-anterior direction (with a sufficiently large anterior component), inferior direction, or inferior-anterior direction, tension in the vocal folds increases, leading to fundamental frequency rise during sustained phonation. On the other hand, pulling in the superior direction, superior-posterior direction, or inferior-posterior direction (with a sufficiently large posterior component) tends to decrease vocal fold tension and phonation fundamental frequency. Varying the pulling force location alters the posture and phonation biomechanics, depending on the force direction. These findings suggest potential roles of particular neck muscles in modulating phonation fundamental frequency, with implications for vocal hyperfunction.

Do-It-Yourself Voice Dosimeter Device: A Tutorial and Performance Results

PURPOSE

Voice dosimeters gather voice production data in the daily lives of individuals with voice disorders. Additionally, voice dosimeters aid in understanding the pathophysiology of voice disorders. Previously, several voice dosimeters were commercially available. However, these devices have been discontinued and are not available to clinicians and researchers alike. In this tutorial, instructions for a low-cost, easy-to-assemble voice dosimeter are provided. This do-it-yourself (DIY) voice dosimeter is further validated based on performance results.

METHOD

Ten vocally healthy participants wore the DIY voice dosimeter. They produced a sustained /a/ vowel and read a text with three different vocal efforts. These tasks were recorded by the DIY voice dosimeter and a reference microphone simultaneously. The expanded uncertainty of the mean error in the estimation of four voice acoustic parameters as measured by the DIY dosimeter was performed by comparing the signals acquired through the reference microphone and the dosimeter.

RESULTS

For measures of sound pressure level, the DIY voice dosimeter had a mean error of -0.68 dB with an uncertainty of 0.56 dB. For fundamental frequency, the mean error was 1.56 Hz for female participants and 1.11 Hz for male participants, with an uncertainty of 0.62 Hz and 0.34 Hz for female and male participants, respectively. Cepstral peak prominence smoothed and L₁ minus L₂ had mean errors (uncertainty) of -0.06 dB (0.27 dB) and 2.20 dB (0.72 dB).

CONCLUSION

The mean error and uncertainties for the DIY voice dosimeter are comparable to those for the most accurate voice dosimeters that were previously on the market.

A mixed-method feasibility study of the use of the Complete Vocal Technique (CVT), a pedagogic method to improve the voice and vocal function in singers and actors, in the treatment of patients with muscle tension dysphonia: a study protocol

BACKGROUND

Muscle tension dysphonia (MTD) results from inefficient or ineffective voice production and is the cause of voice and throat complaints in up to 40% of patients presenting with hoarseness. Standard treatment is voice therapy (SLT-VT) delivered by specialist speech therapists in voice disorders (SLT-V). The Complete Vocal Technique (CVT) is a structured, pedagogic method which helps healthy singers and other performers optimise their vocal function enabling them to produce any sound required. The aim of this feasibility study is to investigate whether CVT administered by a trained, non-clinical CVT practitioner (CVT-P) can be applied to patients with MTD before progressing to a pilot randomised control study of CVT voice therapy (CVT-VT) versus SLT-VT.

METHODS/DESIGN

In this feasibility study, we use a mixed-method, single-arm, prospective cohort design. The primary aim is to demonstrate whether CVT-VT can improve the voice and vocal function in patients with MTD in a pilot study using multidimensional assessment methods. Secondary aims are to assess whether (1) a CVT-VT study is feasible to perform; (2) is acceptable to patients, the CVT-P and SLT-VTs; and (3) whether CVT-VT differs from existing SLT-VT techniques. A minimum of 10 consecutive patients with a clinical diagnosis of primary MTD (types I-III) will be recruited over a 6-month period. Up to 6 video sessions of CVT-VT will be delivered by a CVT-P using a video link. The primary outcome will be a change in pre-/post-therapy scores of a self-reported patient questionnaire (Voice Handicap Index (VHI)). Secondary outcomes include changes in throat symptoms (Vocal Tract Discomfort Scale), acoustic/electroglottographic and auditory-perceptual measures of voice. Acceptability of the CVT-VT will be assessed prospectively, concurrently and retrospectively both quantitatively and qualitatively. Differences from SLT-VT will be assessed by performing a deductive thematic analysis of CVT-P transcripts of therapy sessions.

CONCLUSION

This feasibility study will provide important data to support whether to proceed with a randomised controlled pilot study focusing on the effectiveness of the intervention compared to standard SLT-VT. Progression criteria will be based on demonstrating a positive outcome in treatment, successful delivery of the pilot study protocol, acceptability to all stakeholders and satisfactory recruitment rates.

TRIAL REGISTRATION

ClinicalTrials.gov website ( NCT05365126 Unique Protocol ID: 19ET004). Registered on 06 May 2022.

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.

Effects of Cognitive Stress on Voice Acoustics in Individuals With Hyperfunctional Voice Disorders

PURPOSE

Autonomic nervous system dysfunction has been implicated in the development and persistence of hyperfunctional voice disorders (HVDs). The purpose of this study was to determine the effects of cognitive stress, which is known to arouse the autonomic nervous system, on voice acoustics in female speakers with and without HVDs.

METHOD

Adult female speakers-66 with HVDs, 66 without-were recorded while speaking with and without a cognitive stressor. Root-mean-square (RMS) of amplitude, fundamental frequency (f _o), low-to-high spectral energy ratio (L/H ratio), cepstral peak prominence (CPP), and relative f _o (RFF) were measured for each speaker and cognitive stress condition. Mixed-model analyses of variance and post hoc t tests were conducted to determine if cognitive stress affected voice acoustics and whether voice changes were greater for those with HVDs.

RESULTS

All measures differed significantly under cognitive stress for speakers with and without HVDs. RMS and CPP increased whereas f _o, CPP, and RFF decreased under cognitive stress. Changes in these measures were not greater in those with HVDs.

CONCLUSION

Cognitive stress and presumed autonomic arousal affect voice similarly in female speakers with and without HVDs.

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.

Lombard Effect in Individuals With Nonphonotraumatic Vocal Hyperfunction: Impact on Acoustic, Aerodynamic, and Vocal Fold Vibratory Parameters

PURPOSE

This exploratory study aims to investigate variations in voice production in the presence of background noise (Lombard effect) in individuals with nonphonotraumatic vocal hyperfunction (NPVH) and individuals with typical voices using acoustic, aerodynamic, and vocal fold vibratory measures of phonatory function.

METHOD

Nineteen participants with NPVH and 19 participants with typical voices produced simple vocal tasks in three sequential background conditions: baseline (in quiet), Lombard (in noise), and recovery (5 min after removing the noise). The Lombard condition consisted of speech-shaped noise at 80 dB SPL through audiometric headphones. Acoustic measures from a microphone, glottal aerodynamic parameters estimated from the oral airflow measured with a circumferentially vented pneumotachograph mask, and vocal fold vibratory parameters from high-speed videoendoscopy were analyzed.

RESULTS

During the Lombard condition, both groups exhibited a decrease in open quotient and increases in sound pressure level, peak-to-peak glottal airflow, maximum flow declination rate, and subglottal pressure. During the recovery condition, the acoustic and aerodynamic measures of individuals with typical voices returned to those of the baseline condition; however, recovery measures for individuals with NPVH did not return to baseline values.

CONCLUSIONS

As expected, individuals with NPVH and participants with typical voices exhibited a Lombard effect in the presence of elevated background noise levels. During the recovery condition, individuals with NPVH did not return to their baseline state, pointing to a persistence of the Lombard effect after noise removal. This behavior could be related to disruptions in laryngeal motor control and may play a role in the etiology of NPVH.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20415600.

Wearable Neck Surface Accelerometers for Occupational Vocal Health Monitoring: Instrument and Analysis Validation Study

BACKGROUND

Neck surface accelerometer (NSA) wearable devices have been developed for voice and upper airway health monitoring. As opposed to acoustic sounds, NSA senses mechanical vibrations propagated from the vocal tract to neck skin, which are indicative of a person's voice and airway conditions. NSA signals do not carry identifiable speech information and a speaker's privacy is thus protected, which is important and necessary for continuous wearable monitoring. Our device was already tested for its durable endurance and signal processing algorithms in controlled laboratory conditions.

OBJECTIVE

This study aims to further evaluate both instrument and analysis validity in a group of occupational vocal users, namely, voice actors, who use their voices extensively at work in an ecologically valid setting.

METHODS

A total of 16 professional voice actors (age range 21-50 years; 11 females and 5 males) participated in this study. All participants were mounted with an NSA on their sternal notches during the voice acting and voice assessment sessions. The voice acting session was 4-hour long, directed by a voice director in a professional sound studio. Voice assessment sessions were conducted before, during, and 48 hours after the acting session. The assessment included phonation tasks of passage reading, sustained vowels, maximum vowel phonation, and pitch glides. Clinical acoustic metrics (eg, fundamental frequency, cepstral measures) and a vocal dose measure (ie, accumulated distance dose from acting) were computed from NSA signals. A commonly used online questionnaire (Self-Administered Voice Rating questionnaire) was also implemented to track participants' perception of vocal fatigue.

RESULTS

The NSA wearables stayed in place for all participants despite active body movements during the acting. The ensued body noise did not interfere with the NSA signal quality. All planned acoustic metrics were successfully derived from NSA signals and their numerical values were comparable with literature data. For a 4-hour long voice acting, the averaged distance dose was about 8354 m with no gender differences. Participants perceived vocal fatigue as early as 2 hours after the start of voice acting, with recovery 24-48 hours after the acting session. Among all acoustic metrics across phonation tasks, cepstral peak prominence and spectral tilt from the passage reading most closely mirrored trends in perceived fatigue.

CONCLUSIONS

The ecological validity of an in-house NSA wearable was vetted in a workplace setting. One key application of this wearable is to prompt occupational voice users when their vocal safety limits are reached for duly protection. Signal processing algorithms can thus be further developed for near real-time estimation of clinically relevant metrics, such as accumulated distance dose, cepstral peak prominence, and spectral tilt. This functionality will enable continuous self-awareness of vocal behavior and protection of vocal safety in occupational voice users.

Integrative Review and Framework of Suggested Mechanisms in Primary Muscle Tension Dysphonia

PURPOSE

Despite the high prevalence of primary muscle tension dysphonia (MTD-1), its underlying mechanisms and their interrelationships have yet to be fully identified. The objectives of this integrative review were (a) to describe and classify the suggested underlying mechanisms for MTD-1, (b) to appraise the empirical evidence supporting each of the proposed mechanisms, and (c) to summarize the information in an integrative model.

METHOD

PubMed, Scopus, and CINAHL were searched for all publications pertaining to muscle tension dysphonia. Papers were retained if they included theoretical or empirical data pertaining to underlying mechanisms of MTD-1. A total of 921 papers initially qualified for screening, of which 100 remained for consideration in this review. Underlying mechanisms of MTD-1 were extracted using a consensus approach.

RESULTS

Seven broad categories of putative mechanisms involved in MTD-1 were identified: psychosocial, autonomic, sensorimotor, respiratory, postural, inflammatory, and neuromuscular. These categories were further divided into 19 subcategories detailed in the body of this review article. Based on the reviewed evidence, our proposed integrative model presents MTD-1 as an idiosyncratic motor adaptation to physiological perturbation or perceived threat. Under this model, physiologically or psychologically aversive stimuli can instigate a series of motor adaptations at multiple levels of the nervous system, ultimately disturbing muscle activation patterns and their biomechanical outcomes. Importantly, these adaptations appear to have the potential to become chronic even after threatening stimuli are withdrawn.

CONCLUSIONS

The proposed model highlights the importance of personalized rehabilitation in MTD-1 treatment. Limitations of the literature are discussed to provide guidance for future research aimed at improving our understanding of MTD-1.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.19586065.

Daily Phonotrauma Index: An Objective Indicator of Large Differences in Self-Reported Vocal Status in the Daily Life of Females With Phonotraumatic Vocal Hyperfunction

PURPOSE

The purpose of this study is to evaluate if the Daily Phonotrauma Index (DPI) can quantitatively discriminate large differences in overall vocal status in the daily life of patients with phonotraumatic vocal hyperfunction (PVH).

METHOD

For 1-4 weeks, 23 females with PVH wore an ambulatory voice monitor and answered three vocal status questions (i.e., difficulty producing soft, high-pitched phonation; discomfort; and fatigue) at the beginning, at 5-hr intervals, and the end of each day. DPI values were obtained for each patient's time periods of worst and best self-rated vocal status, and data for the group were analyzed for significant changes using a linear mixed-effects regression model.

RESULTS

The DPI was significantly lower during periods self-rated as "best vocal status" compared to during periods self-rated as "worst vocal status" (mean difference in DPI = 0.53) with a medium-to-large effect size (Cohen's d = -0.68).

CONCLUSIONS

In a group of patients with phonotraumatic lesions, the DPI indicated lower potential for phonotrauma during time periods of better vocal status compared to time periods of worse vocal status. Assuming that a large portion of variance in vocal status for patients with PVH is associated with the extent to which voicing is phonotraumatic, these results support the validity of obtaining estimates of DPI for much shorter time periods (i.e., an estimate every 2 min of voicing) than previous studies (i.e., a single estimate for the entire day or week). Future work can investigate the DPI's use for in-clinic assessment/treatment and ambulatory biofeedback and can gain further insights into phonatory mechanisms that underlie DPI via comparisons with other physiologically relevant measures and computational vocal fold modeling.

Clinical Cutoff Scores for Acoustic Indices of Vocal Hyperfunction That Combine Relative Fundamental Frequency and Cepstral Peak Prominence

PURPOSE

This study examined the discriminative ability of acoustic indices of vocal hyperfunction combining smoothed cepstral peak prominence (CPPS) and relative fundamental frequency (RFF).

METHOD

Demographic, CPPS, and RFF parameters were entered into logistic regression models trained on two 1:1 case-control groups: individuals with and without nonphonotraumatic vocal hyperfunction (NPVH; n = 360) and phonotraumatic vocal hyperfunction (PVH; n = 240). Equations from the final models were used to predict group membership in two independent test sets (n = 100 each).

RESULTS

Both CPPS and RFF parameters significantly improved model fits for NPVH and PVH after accounting for demographics. CPPS explained unique variance beyond RFF in both models. RFF explained unique variance beyond CPPS in the PVH model. Final models included CPPS and RFF offset parameters for both NPVH and PVH; RFF onset parameters were significant only in the PVH model. Area under the receiver operating characteristic curve analysis for the independent test sets revealed acceptable classification for NPVH (72%) and good classification for PVH (86%).

CONCLUSIONS

A combination of CPPS and RFF parameters showed better discriminative ability than either measure alone for PVH. Clinical cutoff scores for acoustic indices of vocal hyperfunction are proposed for assessment and screening purposes.

Triangular body-cover model of the vocal folds with coordinated activation of the five intrinsic laryngeal muscles

Poor laryngeal muscle coordination that results in abnormal glottal posturing is believed to be a primary etiologic factor in common voice disorders such as non-phonotraumatic vocal hyperfunction. Abnormal activity of antagonistic laryngeal muscles is hypothesized to play a key role in the alteration of normal vocal fold biomechanics that results in the dysphonia associated with such disorders. Current low-order models of the vocal folds are unsatisfactory to test this hypothesis since they do not capture the co-contraction of antagonist laryngeal muscle pairs. To address this limitation, a self-sustained triangular body-cover model with full intrinsic muscle control is introduced. The proposed scheme shows good agreement with prior studies using finite element models, excised larynges, and clinical studies in sustained and time-varying vocal gestures. Simulations of vocal fold posturing obtained with distinct antagonistic muscle activation yield clear differences in kinematic, aerodynamic, and acoustic measures. The proposed tool is deemed sufficiently accurate and flexible for future comprehensive investigations of non-phonotraumatic vocal hyperfunction and other laryngeal motor control disorders.

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.

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.

Estimation of Subglottal Pressure, Vocal Fold Collision Pressure, and Intrinsic Laryngeal Muscle Activation From Neck-Surface Vibration Using a Neural Network Framework and a Voice Production Model

The ambulatory assessment of vocal function can be significantly enhanced by having access to physiologically based features that describe underlying pathophysiological mechanisms in individuals with voice disorders. This type of enhancement can improve methods for the prevention, diagnosis, and treatment of behaviorally based voice disorders. Unfortunately, the direct measurement of important vocal features such as subglottal pressure, vocal fold collision pressure, and laryngeal muscle activation is impractical in laboratory and ambulatory settings. In this study, we introduce a method to estimate these features during phonation from a neck-surface vibration signal through a framework that integrates a physiologically relevant model of voice production and machine learning tools. The signal from a neck-surface accelerometer is first processed using subglottal impedance-based inverse filtering to yield an estimate of the unsteady glottal airflow. Seven aerodynamic and acoustic features are extracted from the neck surface accelerometer and an optional microphone signal. A neural network architecture is selected to provide a mapping between the seven input features and subglottal pressure, vocal fold collision pressure, and cricothyroid and thyroarytenoid muscle activation. This non-linear mapping is trained solely with 13,000 Monte Carlo simulations of a voice production model that utilizes a symmetric triangular body-cover model of the vocal folds. The performance of the method was compared against laboratory data from synchronous recordings of oral airflow, intraoral pressure, microphone, and neck-surface vibration in 79 vocally healthy female participants uttering consecutive /pæ/ syllable strings at comfortable, loud, and soft levels. The mean absolute error and root-mean-square error for estimating the mean subglottal pressure were 191 Pa (1.95 cm H2O) and 243 Pa (2.48 cm H2O), respectively, which are comparable with previous studies but with the key advantage of not requiring subject-specific training and yielding more output measures. The validation of vocal fold collision pressure and laryngeal muscle activation was performed with synthetic values as reference. These initial results provide valuable insight for further vocal fold model refinement and constitute a proof of concept that the proposed machine learning method is a feasible option for providing physiologically relevant measures for laboratory and ambulatory assessment of vocal function.

Direct measurement and modeling of intraglottal, subglottal, and vocal fold collision pressures during phonation in an individual with a hemilaryngectomy

The purpose of this paper is to report on the first in vivo application of a recently developed transoral, dual-sensor pressure probe that directly measures intraglottal, subglottal, and vocal fold collision pressures during phonation. Synchronous measurement of intraglottal and subglottal pressures was accomplished using two miniature pressure sensors mounted on the end of the probe and inserted transorally in a 78-year-old male who had previously undergone surgical removal of his right vocal fold for treatment of laryngeal cancer. The endoscopist used one hand to position the custom probe against the surgically medialized scar band that replaced the right vocal fold and used the other hand to position a transoral endoscope to record laryngeal high-speed videoendoscopy of the vibrating left vocal fold contacting the pressure probe. Visualization of the larynx during sustained phonation allowed the endoscopist to place the dual-sensor pressure probe such that the proximal sensor was positioned intraglottally and the distal sensor subglottally. The proximal pressure sensor was verified to be in the strike zone of vocal fold collision during phonation when the intraglottal pressure signal exhibited three characteristics: an impulsive peak at the start of the closed phase, rounded peak during the open phase, and minimum value around zero immediately preceding the impulsive peak of the subsequent phonatory cycle. Numerical voice production modeling was applied to validate model-based predictions of vocal fold collision pressure using kinematic vocal fold measures. The results successfully demonstrated feasibility of in vivo measurement of vocal fold collision pressure in an individual with a hemilaryngectomy, motivating ongoing data collection that is designed to aid in the development of vocal dose measures that incorporate vocal fold impact collision and stresses.