Acoustic correlates of fatigue in laryngeal muscles: findings for a criterion-based prevention of acquired voice pathologies

Cross-Cultural Adaptation and Validation of the Vocal Fatigue Index (VFI) to Danish

OBJECTIVES

The aim was to cross-culturally adapt and validate the Vocal Fatigue Index (VFI) to Danish (DK-VFI).

STUDY DESIGN

Cross-sectional design.

METHODS

The original American English VFI was cross-culturally adapted to Danish using a forward-backward translation procedure combined with focus group interviews. The DK-VFI was distributed to 26 patients with vocal fatigue (VF) and 103 vocally healthy controls. A matched subsample based on age and sex of the control group was included. Internal consistency was determined using Cronbach's alpha and test-retest reliability was determined using Spearman's Rho as well as Wilcoxon signed-rank tests. Validity was confirmed using the Wilcoxon rank-sum test. Sensitivity and specificity were assessed using the Receiver Operating Characteristics test and the discriminative ability was determined using the Area Under the Curve (AUC) test. The original VFI consists of three factors, and cutoff values were calculated for each separate factor in the DK-VFI.

RESULTS

Minor changes were made in the phrasing of specific questions in order to appropriate the VFI to the Danish language. The internal consistency for the DK-VFI was high, with a Cronbach's alpha of α = 0.95. The results showed statistically significant differences (P < 0.05) in mean scores of the DK-VFI between patients and controls. The cutoff values between patients and controls for each separate factor were ≥11.5 for factor 1, ≥2.5 for factor 2, and ≤5.5 for factor 3. The results of the AUC analysis showed that the DK-VFI has discriminative abilities of 0.94 for factor 1, 0.92 for factor 2, and 0.82 for factor 3. Analysis of test-retest reliability showed strong reliability for the patient group and acceptable reliability for the control group.

CONCLUSION

The DK-VFI is a valid and reliable tool for identifying symptoms of VF and can sensitively discriminate people with VF from vocally healthy controls.

Extrinsic Laryngeal Muscle Tension in Primary Muscle Tension Dysphonia with Shear Wave Elastography

OBJECTIVES

It has been assumed that patients with primary muscle tension dysphonia (pMTD) have more extrinsic laryngeal muscle (ELM) tension, but tools to study this phenomenon lack. Shear wave elastography (SWE) is a potential method to address these shortcomings. The objectives of this study were to apply SWE to the ELMs, compare SWE measures to standard clinical metrics, and determine group differences in pMTD and typical voice users before and after vocal load.

METHODS

SWE measurements of the ELMs from ultrasound examinations of the anterior neck, supraglottic compression severities from laryngoscopic images, cepstral peak prominences (CPP) from voice recordings, and self-perceptual ratings of vocal effort and discomfort were obtained in voice users with (N = 30) and without (N = 35) pMTD, before and after a vocal load challenge.

RESULTS

ELM tension significantly increased from rest-to-voiced conditions in both groups. However, the groups were similar in their ELM stiffness levels at SWE at baseline, during vocalization, and post-vocal load. Levels of vocal effort and discomfort and supraglottic compression were significantly higher and CPP was significantly lower in the pMTD group. Vocal load had a significant effect on vocal effort and discomfort but not on laryngeal or acoustic patterns.

CONCLUSION

SWE can be used to quantify ELM tension with voicing. Although the pMTD group reported significantly higher levels of vocal effort and vocal tract discomfort and, on average, exhibited significantly more severe supraglottic compression and lower CPP values, there were no group differences in levels of ELM tension using SWE.

LEVEL OF EVIDENCE

2 Laryngoscope, 133:3482-3491, 2023.

Relationships Between Laryngoscopic Analysis Metrics of Supraglottic Compression and Vocal Effort in Primary Muscle Tension Dysphonia

PURPOSE

Supraglottic compression is thought to underlie vocal effort in patients with primary muscle tension dysphonia (pMTD). However, the relationship between supraglottic compression and vocal effort in this clinical population remains unclear. Gold standard laryngoscopic assessment metrics for supraglottic compression are also lacking. The goals of this study were to identify metrics proposed in the literature that could distinguish patients diagnosed with pMTD from typical voice users and determine their relationships to the vocal effort.

METHODS

Flexible laryngeal endoscopy was performed on 50 participants (25 pMTD, 25 controls). The presence of supraglottic compression was characterized using a categorical (nominal) scale and severity was quantified on ordinal and continuous scales. The three laryngoscopic metrics were correlated with self-perceived ratings of vocal effort on a 100 mm visual analog scale.

RESULTS

Inter-rater reliability was strongest for the continuous scale (P's < 0.0001) compared to categorical (P's < 0.001) and ordinal (P's < 0.001) scales. The presence of different supraglottic compression patterns varied in both groups, and there were no significant group differences on categorical (P's > 0.05) scales. Mediolateral (M-L) supraglottic compression was significantly greater in the pMTD group (P < 0.0001), and anteroposterior (A-P) compression was significantly greater in the control group (P = 0.001) using continuous scales. There were no significant relationships between any of the three laryngoscopic metric types and vocal effort ratings (P's > 0.05), except for a significantly positive relationship between anterior-posterior compression on the ordinal scale and vocal effort in the control group (P = 0.047).

CONCLUSIONS

Continuous scales are reliable and valid for distinguishing individuals with pMTD from those without voice disorders, especially occupational voice users. M-L supraglottic compression may be a better indicator of pMTD than A-P compression. However, the poor correlation between supraglottic compression and vocal effort suggests that one may not influence the other. Future studies should focus on other mechanisms underlying vocal effort in patients with pMTD.

Singing more, singing harsher: occurrence of nonlinear phenomena in a primate' song

Nonlinear phenomena (NLP) in animal vocalizations arise from irregularities in the oscillation of the vocal folds. Various non-mutually exclusive hypotheses have been put forward to explain the occurrence of NLP, from adaptive to physiological ones. Non-human primates often display NLP in their vocalizations, yet the communicative role of these features, if any, is still unclear. We here investigate the occurrence of NLP in the song of a singing primate, the indri (Indri indri), testing for the effect of sex, age, season, and duration of the vocal display on their emission. Our results show that NLP occurrence in indri depends on phonation, i.e., the cumulative duration of all the units emitted by an individual, and that NLP have higher probability to be emitted in the later stages of the song, probably due to the fatigue indris may experience while singing. Furthermore, NLP happen earlier in the vocal display of adult females than in that of the adult males, and this is probably due to the fact that fatigue occurs earlier in the former because of a greater contribution within the song. Our findings suggest, therefore, that indris may be subjected to physiological constraints during the singing process which may impair the production of harmonic sounds. However, indris may still benefit from emitting NLP by strengthening the loudness of their signals for better advertising their presence to the neighboring conspecific groups.

The Adaption to Online Synchronous Teaching and Voice Fatigue: Acoustic and Clinical Data

At the onset of the COVID-19 pandemic in 2020, educators around the world suddenly shifted to online teaching.^, In 2021, we presented research on the impact of this new professional reality on the vocal load of Saint Petersburg State University professors. The online synchronous teaching caused the significant increase in the vocal fatigue in university professors in comparison with the prepandemic studies. We continued our study during the postpandemic semester (winter-spring 2022). The goal of this study was to find out whether adaptation mechanisms during the pandemic period were developed to adjust to the different types of teaching modes. The acoustic and clinical data from the pre/post comparative study are now presented.

Vocal resistance among choir singers

PURPOSE

The purpose of the present study was to compare the voice of choir singers before and after 60 min of singing and after an absolute rest.

METHODS

Twenty-one female choir singers aged on average 26.59 years, with experience in choir singing of at least one year were instructed to emit the vowel /a/ before and after singing and after a vocal rest of 30 min for an analysis of acoustic measures, and for the evaluation of their tactile-kinesthetic self-perception. Vocal warm-up was performed for 10 min. The participants were instructed to sing the "Ave Verum" music continuously for 60 min.

RESULTS

f0 (p = 0.0001) and Flo (p = 0.0002) increased after the singing test and were reduced after the vocal rest, in contrast to Fhi (p = 0.001), which continued to be increased compared to the pre-test measure even after the vocal rest. The vAm parameter (p = 0.05) was reduced after continuous singing and rest. All self-evaluation symptoms increased after the continuous singing task and were reduced after the 30 min rest, except for complaints of low voice, pain when swallowing and cough/throat clearing.

CONCLUSION

60 min of continuous use of the singing voice induced signs of vocal fatigue with an increase in f0, with improvement of symptoms and a reduction of f0 occurring after 30 min of vocal rest.

Toward a Consensus Description of Vocal Effort, Vocal Load, Vocal Loading, and Vocal Fatigue

Purpose The purpose of this document is threefold: (a) review the uses of the terms "vocal fatigue," "vocal effort," "vocal load," and "vocal loading" (as found in the literature) in order to track the occurrence and the related evolution of research; (b) present a "linguistically modeled" definition of the same from the review of literature on the terms; and (c) propose conceptualized definitions of the concepts. Method A comprehensive literature search was conducted using PubMed/MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and Scientific Electronic Library Online. Four terms ("vocal fatigue," "vocal effort," "vocal load," and "vocal loading"), as well as possible variants, were included in the search, and their usages were compiled into conceptual definitions. Finally, a focus group of eight experts in the field (current authors) worked together to make conceptual connections and proposed consensus definitions. Results The occurrence and frequency of "vocal load," "vocal loading," "vocal effort," and "vocal fatigue" in the literature are presented, and summary definitions are developed. The results indicate that these terms appear to be often interchanged with blurred distinctions. Therefore, the focus group proposes the use of two new terms, "vocal demand" and "vocal demand response," in place of the terms "vocal load" and "vocal loading." We also propose standardized definitions for all four concepts. Conclusion Through a comprehensive literature search, the terms "vocal fatigue," "vocal effort," "vocal load," and "vocal loading" were explored, new terms were proposed, and standardized definitions were presented. Future work should refine these proposed definitions as research continues to address vocal health concerns.

[Pretesting of the German Vocal Fatigue Index (VFI-D)-transcultural translation and cross validation]

BACKGROUND

In clinical routine, vocal fatigue is a common symptom in patients with dysphonia.

OBJECTIVE

The aim of this study was to conduct a transcultural translation of the Vocal Fatigue Index (VFI), a standardized subjective questionnaire. Furthermore, pretesting and prevalidation were performed in 20 subjects, with comparison to the Voice Handicap Index (VHI‑9i) and the Vocal Tract Discomfort Scale (VTD).

MATERIALS AND METHODS

The translation, content review, and pretest of the German Vocal Fatigue Index (VFI-D) was divided into four sections: 1. transcultural translation, 2. expert voting on comprehensibility, 3. test of comprehensibility through cognitive interviews in 15 participants, 4. pretest of the VFI‑D with cross validation compared to VHI‑9i and VTD in 20 subjects. This process corresponds to current standards for transcultural translation and adaptation of questionnaires.

RESULTS

According to expert voting and cognitive testing, the VFI‑D is correct and comprehensible (intercoder reliability κ = 0.66). The factor analysis revealed three distinguishable parts: VFI‑D part 1 correlates strongly with VHI‑9i and VTD, VFI‑D part 2 with VTD only (rho ≈ 0.800 each), and VFI‑D part 3 correlates only weakly with VHI‑9i and VTD (rho ≈ 0.585). Thus, convergence and divergence validity are proven.

CONCLUSION

The first German version of the VFI‑D might be a base for further research on symptoms, causes, and treatment options in vocal fatigue. Particularly patients in voice-intensive professions may benefit.

Vocal Dose of Preservice Music Therapists, Preservice Music Teachers, and Other Undergraduate Students

BACKGROUND

Researchers have studied various populations with high vocal doses and prevalence of related voice disorders. Teachers, singers, and university students are three such populations that have been examined extensively. No studies to date, however, have examined the voice use of music therapists and compared their voice use to these other populations.

OBJECTIVE

The purpose of this investigation was to examine voice dosimeter data including phonation duration and percentage, amplitude, frequencies, and distance dose acquired over contiguous 7 day (1 week) periods by preservice music therapists, preservice music teachers, and other university students in concert with daily voice use surveys.

STUDY DESIGN

This is a quantitative descriptive design.

METHODS

Eight female students of varied majors (music therapy, music education, vocal performance, elementary education, and "other") in their third year of university study wore a voice dosimeter during all waking hours for 7 days. The dosimeter recorded voicing time, percentage, frequency, and estimated amplitude. Participants also completed surveys related to several parameters of vocal health, the number of hours they slept, and their voice care.

RESULTS

Participants experienced relatively low vocal doses during the week. Music majors experienced more voice use than nonmusic majors. Some of the highest doses occurred during teaching demonstrations and leading of music therapy practicum sessions.

CONCLUSION

Preservice music therapists and preservice music teachers may experience extreme increases in vocal load when they enter the field. Absent training protocols, these increases could be detrimental to their vocal health and long-term viability as practitioners.

Videokymographic Visualization of Phonasthenia: A Nonorganic Voice Disorder

BACKGROUND

Phonasthenia is a voice disorder where the larynx looks essentially normal and dysphonia is not heard but felt by the patient. This study aims to use videokymography (VKG) to detect any abnormalities in the vibratory pattern in phonasthenia and to find out whether or not these abnormalities change after vocal loading.

METHODS

Thirty-seven phonasthenic patients and 31 normal subjects participated in a detailed protocol, including analysis of subjective complaints and videokymographic quasi-objective parameters (baseline) followed by loading their voices through prolonged loud reading for 45 min. A second evaluation (experimental) was done after loading.

RESULTS

Before vocal loading, patients had significantly more symptoms in all questionnaire questions and higher maximum width difference in VKG than controls. When pre- and postloading values were compared, both groups experienced more symptoms after loading (significant in most of the questions), while the pre- and post-VKG parameters did not show significant differences neither in patients nor controls. On comparing their percent change, the only statistically significant difference between the 2 groups was a greater change in the total score of the questionnaire in the control group.

CONCLUSION

Patients had more vocal fatigue symptoms and more amplitude asymmetry between left and right vocal folds than normal subjects.

Quantifying Vocal Fatigue Recovery: Dynamic Vocal Recovery Trajectories after a Vocal Loading Exercise

Objectives

We quantified the recovery of voice following a 2-hour vocal loading exercise (oral reading).

Methods

Eighty-six adult participants tracked their voice recovery using short vocal tasks and perceptual ratings after an initial vocal loading exercise and for the following 2 days.

Results

Short-term recovery was apparent, with 90% recovery within 4 to 6 hours and full recovery at 12 to 18 hours. Recovery was shown to be similar to a dermal wound healing trajectory.

Conclusions

The new recovery trajectory highlighted by the vocal loading exercise in the current study is called a vocal recovery trajectory. By comparing vocal fatigue to dermal wound healing, this trajectory is parallel to a chronic wound healing trajectory (as opposed to an acute wound healing trajectory). This parallel suggests that vocal fatigue from the daily use of the voice could be treated as a chronic wound, with the healing and repair mechanisms in a state of constant repair. In addition, there is likely a vocal fatigue threshold at which point the level of tissue damage would shift the chronic healing trajectory to an acute healing trajectory.

Assessments of Voice Use and Voice Quality Among College/University Singing Students Ages 18-24 Through Ambulatory Monitoring With a Full Accelerometer Signal

The multiple social and performance demands placed on college/university singers could put their still-developing voices at risk. Previous ambulatory monitoring studies have analyzed the duration, intensity, and frequency (in Hertz) of voice use among such students. Nevertheless, no studies to date have incorporated the simultaneous acoustic voice quality measures into the acquisition of these measures to allow for direct comparison during the same voicing period. Such data could provide greater insight into how young singers use their voices, as well as identify potential correlations between vocal dose and acoustic changes in voice quality. The purpose of this study was to assess the voice use and the estimated voice quality of college/university singing students (18-24 years old, N = 19). Ambulatory monitoring was conducted over three full, consecutive weekdays measuring voice from an unprocessed accelerometer signal measured at the neck. From this signal, traditional vocal dose metrics such as phonation percentage, dose time, cycle dose, and distance dose were analyzed. Additional acoustic measures included perceived pitch, pitch strength, long-term average spectrum slope, alpha ratio, dB sound pressure level 1-3 kHz, and harmonic-to-noise ratio. Major findings from more than 800 hours of recording indicated that among these students (a) higher vocal doses correlated significantly with greater voice intensity, more vocal clarity and less perturbation; and (b) there were significant differences in some acoustic voice quality metrics between nonsinging, solo singing, and choral singing.

Speech Adjustments for Room Acoustics and Their Effects on Vocal Effort

OBJECTIVES

The aims of the present study are (1) to analyze the effects of the acoustical environment and the voice style on time dose (D_{t_p}) and fundamental frequency (mean f₀ and standard deviation std_f₀) while taking into account the effect of short-term vocal fatigue and (2) to predict the self-reported vocal effort from the voice acoustical parameters.

METHODS

Ten male and ten female subjects were recorded while reading a text in normal and loud styles, in three rooms-anechoic, semi-reverberant, and reverberant-with and without acrylic glass panels 0.5 m from the mouth, which increased external auditory feedback. Subjects quantified how much effort was required to speak in each condition on a visual analogue scale after each task.

RESULTS

(Aim1) In the loud style, D_{t_p}, f₀, and std_f₀ increased. The D_{t_p} was higher in the reverberant room compared to the other two rooms. Both genders tended to increase f₀ in less reverberant environments, whereas a more monotonous speech was produced in rooms with greater reverberation. All three voice parameters increased with short-term vocal fatigue. (Aim2) A model of the vocal effort to acoustic vocal parameters is proposed. The sound pressure level contributed to 66% of the variance explained by the model, followed by the f₀ (30%) and the modulation in amplitude (4%).

CONCLUSIONS

The results provide insight into how voice acoustical parameters can predict vocal effort. In particular, it increased when SPL and f₀ increased and when the amplitude voice modulation decreased.

Effect of the tracheoesophageal voice resistance test in total laryngectomees

OBJECTIVES/HYPOTHESIS

To analyze tracheoesophageal voice resistance in laryngectomized patients by comparing the acoustic, perceptive-auditory and self-evaluation measures before and after the voice resistance test.

STUDY DESIGN

An observational, experimental study with a quantitative and descriptive approach.

METHODS

Nineteen total laryngectomees were submitted for capture of vocal intensity, self-assessment of signs and symptoms of voice fatigue using a visual analogue scale, and perceptive-auditory and acoustic analysis of the tracheoesophageal voice before and after the voice resistance test, which consisted of continuous repeated counting from one to 100.

RESULTS

The mean time of execution of the test was 33.68 minutes. Type II sound signal, voice intensity, voice quality, degree of severity of dysphonia, and the pitch and loudness parameters were maintained after the test. There were no changes in signs and symptoms of vocal fatigue.

CONCLUSIONS

Most of the total laryngectomees performed the voice resistance test for less than 30 minutes. However, the voice resistance test did not induce significant changes in the quality of tracheoesophageal voice of total laryngectomees or in the signs and symptoms of vocal fatigue.

LEVEL OF EVIDENCE

4 Laryngoscope, 2016 127:405-410, 2017.

Phonatory function after prolonged voice use in Brazilian woman

OBJECTIVES

To evaluate the behavior of the phonatory function and the perceived strain in Brazilian young women, before and after a test of prolonged voice use test, for a period of one continuous hour.

METHODS

Twenty young women without laryngeal disorders participated in the study and were submitted to vocal acoustic analysis (MDVP-Advanced, CSL-Kay Pentax®), perceptual voice assessment, carried out by five judges, and the measurement of speech-strain level using a visual analog scale before and after a prolonged use of the voice, from the reading of a standardized text for one hour in usual vocal intensity and frequency, without breaks for hydration or vocal rest. The description and comparison between the variables and the appropriate statistical analysis were carried out.

RESULTS

The acoustic parameters of fundamental (f0) and low frequency (Flo) of the emission increased after 1 hour of voice use, while the values for the amplitude tremor intensity index (Atri), amplitude variation (vAm), noise-to-harmonic ratio (NHR), and soft phonation index (SPI) were reduced after the prolonged voice use test. The judges agreed with the decrease in the overall level of dysphonia (kappa=0.66), roughness (kappa=0.59), and vocal breathiness (kappa=0.73); increased phonatory stability (kappa=0.64); vocal projection (kappa=0.48); pitch (kappa=0.74); and loudness (kappa=0.65). The phonatory strain increased significantly after the test (p=0.003).

CONCLUSION

One hour of prolonged voice use seems to favor laryngeal adaptation and increased adductor muscle activity to maintain vocal efficiency. However, the self-perception of vocal strain is evident and can be understood as a sign of muscle fatigue caused by continuous use.

Nonlinear analyses of elicited modal, raised, and pressed rabbit phonation

OBJECTIVES/HYPOTHESIS

The purpose of this study was to use nonlinear dynamic analysis methods such as phase space portraits and correlation dimension (D2) as well as descriptive spectrographic analyses to characterize acoustic signals produced during evoked rabbit phonation.

METHODS

Seventeen New Zealand white breeder rabbits were used to perform the study. A Grass S-88 stimulator (SA Instrumentation, Encinitas, CA) and constant current isolation unit (Grass Telefactor, model PSIU6; West Warwick, RI) were used to provide electrical stimulation to laryngeal musculature, and transglottal airflow rate and stimulation current (mA) were manipulated to elicit modal, raised intensity, and pressed phonations. Central 1 second portions of the most stable portion of the acoustic waveform for modal, raised intensity, and pressed phonations were edited and then analyzed via phase space portraits, Poincaré sections, and the estimation of the D2. In an attempt to limit the effects of the highly variable and nonstationary characteristics of some of the signals being analyzed, D2 analysis was also performed on the most stable central 200-millisecond portion of the acoustic waveform. Descriptive analysis of each phonation was also conducted using sound spectrograms.

RESULTS

Results showed that the complexity of phonation and the subsequent acoustic waveform is increased as transglottal airflow rate and degree of glottal adduction are manipulated in the evoked rabbit phonation model. In particular, phonatory complexity, as quantified via D2 analyses and demonstrated via spectrographic characteristics, increases from "modal" (ie, phonation elicited at just above the phonation threshold pressure) to raised intensity (phonation elicited by increasing transglottal airflow rate) to pressed (phonation elicited by increasing the stimulation current delivered to the larynx). Variations in a single dynamic dimension (airflow rate or adductory force) resulted in significantly increased productions of nonlinear phenomenon, including bifurcations from periodicity to regions of subharmonic content, fundamental frequency, and harmonic jumps, and evidence of periodicity within aperiodic regions ("chaos").

CONCLUSIONS

The evoked rabbit phonation model described in this study allows for the elicitation of various types of phonations under controlled conditions and, therefore, has the potential to provide insight regarding important variables that may elicit examples of nonlinear phenomena such as subharmonics and deterministic chaos.