Potential Biophysiological Mechanisms Underlying Vocal Demands and Vocal Fatigue

Effects of Back Pressure on the Feasibility and Tolerability of Laryngeal Diadochokinetic Exercise: A Pilot Study

BACKGROUND

The term vocal demand response refers to how speakers meet vocal demands. Vocal loading tasks with predetermined demand parameters (duration, pitch, loudness, etc) have been used in research to study the vocal demand response; these have historically consisted of loud sustained vowel and loud speech tasks. Tasks founded on laryngeal diadochokinesis (LDDK) may be viable alternatives, especially if demand parameters such as exercise-rest ratio and fluid back pressure are concurrently modulated.

OBJECTIVES

To explore the effects of four fluid back pressure conditions (0, 5, 10, and 15 cm H2O) on several measures of subjective participant experience, feasibility, and tolerability during intervallic laryngeal diadochokinetic exercise.

METHODS

Participants (n = 12) completed 15-minute trials of LDDK in 30-second rest and exercise intervals against four counterbalanced back pressure conditions: 0, 5, 10, and 15 cm H2O. The effects of back pressure on (1) ratings of perceived vocal exertion, (2) prevalence of adverse effects such as shortness of breath or lightheadedness, (3) subjective difficulty of sustaining LDDK, (4) number of exercise intervals completed, (5) rankings of participant-preferred back pressure levels, and (6) expert ratings of auditory-perceptual diadochokinetic strength were assessed descriptively.

RESULTS

Perceived vocal exertion, lightheadedness, and subjective laryngeal diadochokinetic difficulty increased as back pressure increased. Number of intervals completed, auditory-perceptual diadochokinetic strength, and participant rankings of back pressure conditions, by contrast, decreased as back pressure increased. 0 and 5 cm H2O were the most preferred back pressure conditions overall.

DISCUSSION

Fluid back pressure was feasible and broadly tolerated during 15-minute trials of vocal exercise. However, the transition from 5 → 10 cm H2O appeared to represent an inflection point in our results: a minority of participants did not tolerate exercise at 10 cm H2O, becoming a majority at 15 cm H2O. We conclude that fluid back pressure should be restricted to values between 0 and 10 cm H2O during LDDK.

A Tutorial on Skeletal Muscle Metabolism and the Role of Blood Lactate: Implications for Speech Production

PURPOSE

The purpose of this tutorial is threefold: (a) present relevant exercise science literature on skeletal muscle metabolism and synthesize the limited available research on metabolism of the adult human speech musculature in an effort to elucidate the role of metabolism in speech production; (b) introduce a well-studied metabolic serum biomarker in exercise science, lactate, and the potential usefulness of investigating this metabolite, through a well-established exercise science methodology, to better understand metabolism of the musculature involved in voice production; and (c) discuss exercise physiology considerations for future voice science research that seeks to investigate blood lactate and metabolism in voice physiology in an ecologically valid manner.

METHOD

This tutorial begins with relevant exercise science literature on the basic cellular processes of muscle contraction that require energy and the metabolic mechanisms that regenerate the energy required for task execution. The tutorial next synthesizes the available research investigating metabolism of the adult human speech musculature. This is followed by the authors proposing a hypothesis of speech metabolism based on the voice science literature and the application of well-studied exercise science principles of muscle physiology. The tutorial concludes with a discussion and the potential usefulness of lactate in investigations to better understand the metabolism of the musculature involved in vocal demand tasks.

CONCLUSION

The role of metabolism during speech (respiratory, laryngeal, and articulatory) is an understudied yet critical aspect of speech physiology that warrants further study to better understand the metabolic systems that are used to meet vocal demands.

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.

Reducing Vocal Fatigue With Bone Conduction Devices: Comparing Forbrain and Sidetone Amplification

PURPOSE

Altered auditory feedback research aims to identify methods to strengthen speakers' awareness of their own voicing behaviors, diminish their perception of vocal fatigue, and improve their voice production. This study aims to compare the effects of two bone conduction devices that provide altered auditory feedback.

METHOD

Twenty participants (19-33 years old, age: M [SD] = 25.5 [3.85] years) participated in a vocal loading task using a standard Forbrain device that provides filtered auditory feedback via bone conduction and a modified Forbrain device that provides only sidetone amplification, and a control condition with no device was also included. They rated their vocal fatigue on a visual analog scale every 2 min during the vocal loading task. Additionally, pre- and postloading voice samples were analyzed for acoustic voice parameters.

RESULTS

Across all participants, the use of bone conduction-altered auditory feedback devices resulted in a lower vocal fatigue when compared to the condition with no feedback. During the pre- and postvoice samples, the sound pressure level decreased significantly during feedback conditions. During feedback conditions, spectral mean and standard deviation significantly decreased, and spectral skew significantly increased.

CONCLUSION

The results promote bone conduction as a possible preventative tool that may reduce self-reported vocal fatigue and compensatory voice production for healthy individuals without voice disorders.

Cross-cultural adaptation and validation of vocal fatigue index (VFI) to Chinese language

Objectives: This study aimed to translate the Vocal Fatigue Index (VFI) into Simplified Chinese and test its reliability and validity in mainland China. Methods: The original English version of the VFI was translated and adapted to a Simplified Chinese version (VFI -SC). Fifty-four participants with voice disorders and 21 healthy controls completed the VFI-SC. Sixteen participants with voice disorders completed it again two weeks later. Reliability, validity, and receiver operating characteristic (ROC) of the VFI-SC were analyzed. Results: The Cronbach's alpha values for the VFI factor scores were found to be 0.930 for tiredness and avoidance of voice use (factor 1), 0.878 for physical discomfort with voice use (factor 2), and 0.915 for improvement of symptoms with voice rest (factor 3). The test-retest reliability was 0.967 for all three factors. There was a significant difference between the total scores of the patient group and the control group (p < 0.01). Factor 1 and factor 2 were positively correlated with the Voice Handicap Index (VHI-30). The ROC curves showed acceptable intrinsic accuracies for factor 1 (AUC = 0.883), factor 2 (AUC = 0.901), and factor 3 (AUC = 0.800), with cutoff scores of 22, 7, and 9, respectively. Conclusions: This study provides preliminary evidence that the VFI-SC has good reliability and validity. It can be used to screen for clinical symptoms of voice fatigue in mainland China.

It Sounds like It Feels: Preliminary Exploration of an Aeroacoustic Diagnostic Protocol for Singers

To date, no established protocol exists for measuring functional voice changes in singers with subclinical singing-voice complaints. Hence, these may go undiagnosed until they progress into greater severity. This exploratory study sought to (1) determine which scale items in the self-perceptual Evaluation of Ability to Sing Easily (EASE) are associated with instrumental voice measures, and (2) construct as proof-of-concept an instrumental index related to singers' perceptions of their vocal function and health status. Eighteen classical singers were acoustically recorded in a controlled environment singing an /a/ vowel using soft phonation. Aerodynamic data were collected during a softly sung /papapapapapapa/ task with the KayPENTAX Phonatory Aerodynamic System. Using multi and univariate linear regression techniques, CPPS, vibrato jitter, vibrato shimmer, and an efficiency ratio (SPL/PSub) were included in a significant model (p < 0.001) explaining 62.4% of variance in participants' composite scores of three scale items related to vocal fatigue. The instrumental index showed a significant association (p = 0.001) with the EASE vocal fatigue subscale overall. Findings illustrate that an aeroacoustic instrumental index may be useful for monitoring functional changes in the singing voice as part of a multidimensional diagnostic approach to preventative and rehabilitative voice healthcare for professional singing-voice users.

Patient Profiling: Determining the Effects of Patient Factors on Vocal Fatigue

OBJECTIVES

The phenomenon of vocal fatigue and the types of patients that are at greatest risk for vocal fatigue are not fully understood. The goal was to investigate patient profiles such as voice disorder type, demographics (age and gender), singing identity, interoceptive awareness, and psychosocial impacts on the severity of vocal fatigue.

STUDY DESIGN

Prospective cohort study.

METHODS

Ninety-five subjects with voice disorders were asked to complete Part 1 of the Vocal Fatigue Index (VFI-Part1), the Voice Handicap Index-10 (VHI-10), and the Multidimensional Assessment of Interoceptive Awareness, version 2 (MAIA-2). The effects of voice disorder type (structural, neurological, functional), psychosocial impact, age, gender, self-reported singing identity, and interoceptive awareness on self-perceived vocal fatigue (VFI-Part1) were determined using multivariate linear regression.

RESULTS

Vocal fatigue had a significant psychosocial impact on patients with voice disorders, as measured by the VHI-10 (P < 0.001). However, there were no significant effects of vocal fatigue across any of the three voice disorder types (P's >0.05). Age (P = 0.220), gender (P = 0.430), and self-identified singing experience (P = 0.360) also did not have significant effects on vocal fatigue. Additionally, there were no significant relationships between interoceptive awareness MAIA-2 sum scores (P = 0.056) or any of the MAIA-2 sub-scores (P's > 0.05) and vocal fatigue severity (VFI-Part1).

CONCLUSION

Vocal fatigue has a significant psychosocial impact on patients with voice disorders. However, patient profiles, including voice disorder type, patient age, gender, singing identity, and level of interoceptive awareness do not appear to play a major role in vocal fatigue symptom reporting. These findings suggest caution should be exercised when attributing patient profiles to vocal fatigue presentation and severity. Studying pathophysiological mechanisms underlying vocal fatigue may help better distinguish unconscious bias in patient profiling from the etiology and severity of vocal fatigue.

Interoception, Voice Symptom Reporting, and Voice Disorders

OBJECTIVES

Interoception may play a role in how individuals perceive their voice disorder. The first objective of this study was to investigate relationships between interoception and voice disorder class (functional, structural, neurological). The second objective was to determine relationships between interoception and voice-related outcome measures between patients with functional voice and upper airway disorders and typical voice users. The third objective was to determine whether patients with primary muscle tension dysphonia (a type of functional voice disorder) had different levels of interoceptive awareness than typical voice users.

STUDY DESIGN

Prospective cohort study.

METHODS

One hundred subjects with voice disorders completed the multidimensional assessment of interoceptive awareness-2 (MAIA-2). Voice diagnosis and singing experience were also acquired from each patient's medical chart. Voice handicap (VHI-10) and Part 1 of the vocal fatigue index (VFI-Part1) scores were obtained from patients diagnosed with functional voice and upper airway disorders. MAIA-2, VHI-10, VFI-Part1, and singing experience were also obtained from 25 typical voice users. Multivariable linear regression models were used to assess the association between response variables and voice disorder class, adjusting for singing experience, gender, and age.

RESULTS

There were no significant group differences between voice disorder class (functional, structural, neurological) after adjusting for multiple comparisons. Participants with functional voice and upper airway disorders who scored significantly higher on the VHI-10 and VFI-Part1 had lower Attention Regulation sub-scores on the MAIA-2 (P's<0.05). Patients with primary muscle tension dysphonia scored significantly lower on the Emotional Awareness MAIA-2 subscale than typical voice users (P=0.005).

CONCLUSION

Patients with functional voice disorders with lower capabilities to attend to body sensations may score higher on voice-related patient-reported outcome measures, like the VHI-10 and VFI-Part1. Patients with primary muscle tension dysphonia may also have lower capabilities in processing their body sensations than typical voice users.

The Effects of Room Acoustics on Self-reported Vocal Fatigue: A Systematic Review

PURPOSE

The main objective of the present systematic review is to quantify the relationship between the room acoustics and self-reported vocal fatigue.

METHODS

A comprehensive literature search and systematic review were conducted using PubMed/MEDLINE, Science Direct, Web of Science, EBSCO, and Scopus databases. Two inclusion criteria were defined: (1) description of a relationship between the room acoustics and self-reported vocal fatigue; and (2) reporting of raw data and/or a statistic of the association between the variables. Risk of bias in the included studies was assessed via the Quality Assessment Tool for Quantitative Studies Effective Public Health Practice Project. The occurrences and frequencies of the most common parameters in the literature are presented, and a quantitative summary of their relationships is reported.

RESULTS

In total, 12 publications met the inclusion criteria. The most relevant measures of self-reported vocal fatigue were the Vocal Fatigue Index (n = 3), Vocal Signs and Symptoms Questionnaire (n = 1), and vocal fatigue visual analog scales (n = 2). The most relevant room acoustic parameters include noise conditions (n = 6) and reverberation time (n = 2). The relationships between the room acoustic parameters and self-reported vocal fatigue are quantified and reported while maintaining the concepts stated in the original articles and outlining their similarities.

CONCLUSION

Overall, background noise and reverberation time were determined to be the most significant independent variables associated with self-reported vocal fatigue. A primary limitation of the evidence was inconsistent measures of self-reported vocal fatigue.