Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2024 Mar 28.
Published in final edited form as: Perspect ASHA Spec Interest Groups. 2021 Jan 5;6(1):69–79. doi: 10.1044/2020_persp-20-00258

Do We Need a Measure of Vocal Effort? Clinician’s report of vocal effort in voice patients

Miriam van Mersbergen 1,2, Bethany Helen Beckham 1, Eric J Hunter 3
PMCID: PMC10977929  NIHMSID: NIHMS1972074  PMID: 38549948

Abstract

Purpose:

Vocal effort has been of increasing interest to voice clinicians and researchers. However, little is known about the prevalence of vocal effort in voice patients presenting to voice clinics. The purpose of this study was to better understand how vocal effort is perceived and used in a clinical setting, including the current opinions on this symptom and experiences of voice clinicians regarding vocal effort measurement and management.

Method:

Speech language pathologists who regularly treat voice patients were queried about their years of voice experience, number of voice patients treated yearly, percentage of voice patients who complain of vocal effort, methods of clinically measuring vocal effort, and treatment strategies that address vocal effort in therapy.

Results:

Survey results revealed that vocal effort is a commonly presented complaint in the voice clinic with over two-thirds of clinicians reporting that the majority of their patients complain of vocal effort and approximately 25% of clinicians reporting that vocal effort is the main complaint in their patients. Although most clinicians measure vocal effort in the clinic, very few use a dedicated vocal effort measure. About half of the clinicians reported that they specifically address vocal effort reduction as a therapy goal.

Conclusion:

Despite the high prevalence of observed vocal effort complaints in patients and the focus of vocal effort reduction in therapy, there is no standardized measure of vocal effort widely utilized in the clinic. Future research should address clinically tractable methods to measure vocal effort validly and reliably.

Keywords: Vocal Effort, Voice Disorders, Vocal Effort Measurement

Introduction

What is Vocal Effort?

Vocal effort is a ubiquitous symptom in voice clinics. Despite its prevalence, it has been difficult to precisely define what vocal effort is. Indeed, there are many names that have been used as synonyms to vocal effort, such as perceived phonatory exertion or effort (Chang & Karnell, 2004; Gilman & Johns, 2017) or vocal fatigue (N.P. Solomon et al., 2003; Nancy Pearl Solomon, 2008a). Further adding to the confusion, the term vocal effort has discussed in terms of a range of perspectives. For example the term has been used to define the perception of the listener when assessing a voice with strain (Brandt et al., 1969; Eadie et al., 2017; Isetti et al., 2014; Liénard & Di Benedetto, 1999) or the perception of the speaker’s physical strength to create sound. (Ford Baldner et al., 2015). Thus, effort has been used to define perceptions from both the listener and speaker alike, reflecting vagueness to about the underlying mechanisms of vocal effort. This lack of consistency in use and definition has led to much confusion and debate about what physiological conditions lead to the symptom or experience of vocal effort (Bottalico, 2017; Bottalico et al., 2016a; Colton & Brown, 1973; Giovanni et al., 2008; Lagier et al., 2010; Leeper & Noll, 1972; McKenna & Stepp, 2018; Rosenthal et al., 2014), how to measure vocal effort (Ford Baldner et al., 2015), when to measure vocal effort (during a task or in retrospect of many tasks), or how to track its changes throughout the therapy session (van Leer & van Mersbergen, 2017). Other questions arise about the type of patients who present with vocal effort (Eadie & Stepp, 2013; Johnson & Eadie, 2012; Sampaio et al., 2012; Searl & Knollhoff, 2018; Shoffel-Havakuk et al., 2019) and how important vocal effort is to them. To add to the confusion, these questions are also compounded by the observations that patients are sometimes not aware of the effort put forth in voicing until after a few sessions of therapy, suggesting that more than a physiological phenomenon, effort is influenced by psychological conditions. So how exactly are we to figure out how to measure vocal effort when given an unclear definition and a seemingly transient and unpredictable presentation?

A recent literature review and consensus paper (Hunter et al., 2020) tracked the use of the term vocal effort, along with the following terms: vocal fatigue, vocal load, and vocal loading. This endeavor lead to consensus definitions of these terms based on their usage in the voice literature. Additionally, definitions were modeled after related fields such as ergonomics (Borg, 2007; Borg, 1982, 1990), exercise physiology (Pageaux, 2016; Razon et al., 2020; Tenenbaum & Eklund, 2007), and speech acoustics (Bottalico et al., 2016b). The consensus paper highlighted that vocal effort was a perceptual phenomenon. With this perspective, in the context of a need to communicate (vocal demand), there is the physical event (voice production), the perception of the speaker of producing voice (vocal effort), and the perception of the production by the listener (vocal strain). In other words, vocal effort is a perception of the work or exertion an individual feels during phonation. Furthermore, unlike other perceptual phenomena (such as pitch) that has a simple physical correlate (frequency), vocal effort is a global perception that encompasses multiple physical correlates. Unfortunately, the multifactorial nature of vocal effort presents challenges in developing a valid, reliable measurement tool.

The multifactorial contributions to vocal effort are clearly observed in the literature. Physiological contributions to vocal effort include subglottal pressure measurements, such as phonation threshold pressure (Chang & Karnell, 2004) and transglottal airflow (Rosenthal et al., 2014) have been found to correlate with reports of increased effort. Additionally, psychological measures such as mood (van Mersbergen & Delany, 2014), arousal (van Mersbergen et al., 2017), and cognitive load (Vinney et al., 2016) have shown increases in vocal effort. Given that vocal effort varies in different physiological and psychological states, a vocal effort measure needs to be both sensitive to these contributions while maintaining its specificity in reflecting perceived exertion. Future research establishing such as measure should improve our understanding of how patients experience vocal effort.

Effort Measurement Techniques

Typically, psychophysical phenomena are measured using a number of scaling techniques (Stevens, 1958, 1971) that require an individual to assign a numbered value to a psychological phenomenon: in this case, perception of effort. There are a number of different types of scaling techniques such as estimation scales, difference scales, and threshold scales (Thurstone, 2017). Estimation scales belong to a category of scales called ratio scales. The most common type of estimation scale in our field is the Direct Magnitude Estimation scale where individuals assign a number to represent their perceived level of a physical stimulus. For example, participants in a hearing experiment would hear a tone presented at a given frequency and intensity level (for example, 50 dB at 1000 Hz) and assign number to represent their perceived loudness (45 phons). Another estimation scale is Direct Magnitude Production, which is the opposite of Direct Magnitude Estimation. In Direct Magnitude Production, individuals are given a specific level of a stimulus (vocal effort level of 15) and they are asked to vocally produce this level. Difference scales such as Just Noticeable Difference measure the level a physical stimulus needs to change for an individual to perceive it as different from another stimulus at least 50% of the time. Anyone who has ever undergone a vision assessment is familiar with the process of determining just noticeable differences between seeing through one set of lenses and another set. A narrowly employed version of a difference scale is the level of a stimulus necessary to detect its presence, called a threshold. Threshold levels are frequently employed in the measurement of hearing acuity. These scaling methods have robust methods and mathematical estimations for determining perception. However, in determining the perception of vocal effort, determining the precise physical stimulus or complex of stimuli is necessary. However, our understanding the physical and physiological contributions to vocal effort remains incomplete.

As stated earlier, the multifactorial nature of vocal effort presents drawback to these scaling methods due to the assumption that the physical correlate(s) are known and can be systematically manipulated. Our field is still determining what contributes to vocal effort and its physical correlates remain unknown. In the absence of known physical correlates, clinicians and researchers employ other scaling techniques such as Likert and Likert-type scales, semantic differentiation scales, and visual analogue scales. Likert scales and Likert-type scales typically are the sum of many questions that require an individual to rate the level of agreement he or she has to a statement. These levels are presented as statements such as “strongly agree” to “strongly disagree” and usually have a neutral choice mid-way between each polar end. Likert scales rely on strict criteria of the distribution of levels to enable mathematical comparisons between statements and between respondents. Specifically, they must be equally weighted around a mid-point or endpoint and the distance between two responses should represent the same distance between any other two other points on the scale. Semantic differentiation scales are similar to Likert scales in that participants choose a level between two polar ends. However, instead of the polar ends representing a level of agreement, the polar ends have a word and its comparative antonym for comparison. For example, a scale may ask a question about the likability of a person in a photograph and require an individual to choose a level between “friendly” and “aloof.” Visual analogue scales offer the individual more freedom when rating a level of experience by allowing the rater to indicate on a continuous line. Visual Analogue scales usually employ a 10 cm line with lexical or pictorial anchors at each end and throughout the scale to constrain the variability between respondents. The drawback to these scales is that many of them cannot be manipulated mathematically, meaning that statistical inferences cannot be made without careful manipulation of the data. Even though we have a definition for vocal effort that can be employed in future clinical and research activities, the challenge of measuring effort still requires work to determine which scales to use and anchors to employ.

However, there are some initial suggestions on how to measure vocal effort that follow the consensus definition. Unlike vocal fatigue, which is a decline in performance or perception over time (Hunter et al., 2020; Nancy Pearl Solomon, 2008), vocal effort is an in-the-moment phenomena (G. Borg, 1990) and thus should be measured immediately following vocal production. Furthermore, because vocal effort varies with known psychological conditions such as mood (van Mersbergen et al., 2008; van Mersbergen & Delany, 2014; van Mersbergen et al., 2017) or cognitive load (van Mersbergen et al., 2019), these conditions should be controlled when measuring vocal effort. In summary, vocal effort should be measured immediately following a vocal activity while keeping other psychological influences stable, or at least, noted.

These suggestions are a good place to begin developing a measure of vocal effort. However, to justify the development of a measure of vocal effort, we need to know the prevalence of this symptom. Unfortunately, without a good measurement tool, it is difficult to gather epidemiological data on vocal effort. This tautological conundrum is hard to circumvent. However, one necessary step forward towards developing a vocal effort measurement tool is to gather information from professionals working with “people with voice disorders”. The purpose of this study was to survey vocal health professionals to establish an understanding on how vocal effort is perceived and used in a clinical setting. The results of this study support further study of vocal effort and the need to have a standard, reliable, and valid tool that is clinically applicable.

Methods

Participants

Participants for this research were speech language pathologists and voice teachers who were members of the American Speech-Language Hearing Association’s Special Interest Group – 3, the “voice” listserv though the University of Iowa, or both. Participants were invited to participate in this study as part of a professional survey about experiences and opinions of speech language pathologists with respect to vocal effort. The study was reviewed by the University of Memphis IRB (protocol number PRO-FY2020-433) and was determined exempt.

Survey

The survey was distributed via online posts to the online professional forums above with a link to Qualtrics; all data were deidentified at the time of collection. The survey contained sixteen questions that were mostly forced choice with some options to add free text information. The questionnaire included: [a] professional demographic questions (e.g. number of years in the profession), [b] professional practice questions (e.g. percentage of caseload that included voice or other disorders), [c] patient related questions (e.g. prevalence and types of patient vocal effort complaints), and [d] vocal effort related questions (e.g. language to describe vocal effort, vocal effort measurement tools, therapy techniques to modify vocal effort, opinions about vocal effort).

Analysis

Data collected underwent a simple tally with numbers and percentages reported for all questions. Given the descriptive nature of this survey, no inferential statistics were computed.

Results

One hundred twenty-one professionals responded. Three of these were excluded, as less than 10% of questions were completed, for a total of 118 responses for analysis. Of these 118 responses, only 85 participants completed every question of the survey.

Demographics and Caseload (n=number of participants)

Of the 118 responses, more than 70% of respondents were speech-language pathologists (n=86), 4% were teachers of singing (n=5), and 23% were both speech-language pathologists and teachers of singing (n=27). The largest percentage at thirty-nine percent of respondents (n=37 of 97 respondents) had been clinicians for more than 25 years, followed by twenty-one percent that had been clinicians for 0-5 years (n=20; see Figure 1). Of these same responses, almost one third of clinicians (n=30) reported that their caseload was composed of 90-100% voice. Sixty-one percent of survey respondents (n=59) see upwards of 70% voice patients (see Figure 2).

Figure 1.

Figure 1.

Open in a new tab

Responses to “How long have you been a clinician?”

Figure 2.

Figure 2.

Open in a new tab

Responses to “What percentage of your caseload is voice for a typical year?”

From 95 responses about patient caseload in addition to voice, seventy-six percent of respondents (n=72) work with behavioral breathing and cough disorders. More than half of respondents (n=52) serve the swallowing population, thirty-nine percent see head and neck patients (n=67), twenty-eight percent serve the motor speech (n=27), and twenty-four percent work with the adult cognition and language (n=23) populations. See Table 1 for a breakdown of other populations served.

Table 1.

Other populations served besides voice disorders (n=95)

Other populations served Respondents n % of total
Behavioral Breathing/ Cough Disorders 72 76
Swallowing 52 55
Head and Neck 37 39
Motor Speech 27 28
Other 23 24
Adult Cognition and Language 23 24
Cleft Palate/ Craniofacial 5 5
Open in a new tab

Percentage of Vocal Effort Problems in Caseload (n=89)

Almost two-thirds of clinicians (n=56) report voice caseloads where more than half of patients report problems with vocal effort (see Figure 3). Respondents varied widely on whether vocal effort was the main symptom of their patients. Twenty-four respondents reported that the majority of their patients report vocal effort as their main symptom (see Figure 4).

Figure 3.

Figure 3.

Open in a new tab

Responses to “What percentage of your voice caseload reports problems with vocal effort?”

Figure 4.

Figure 4.

Open in a new tab

Responses to “What percent of your voice caseload reports that vocal effort is the main symptom?”

When asked how often vocal effort was the only symptom, forty percent of professional respondents (n=36) said vocal effort was the only symptom in 1-10% of their caseload and another forty percent reported a greater proportion of patients reported vocal effort as the only symptom (n=36; see Figure 5).

Figure 5.

Figure 5.

Open in a new tab

Responses to “What percent of your voice caseload reports that vocal effort is the only symptom?”

Explaining Vocal Effort (n=89)

Sixty percent of respondents (n=53) said that their patients sometimes had difficulty explaining vocal effort to them. Twenty-nine percent (n=26) reported that they sometimes had difficulty explaining what vocal effort was to their patients. Clinicians were asked to explain how their patients describe vocal effort, regardless of whether they use the actual term “vocal effort.” The most popular terms were strain (n=32), hard (n=32), work (n=24), push (n=21), tired/tiring (n=20), fatigue (n=13), effort (n=14), exhausting (n=7), pain (n=4), force (n=4), and tight (n=4).

Clinicians were also asked to write how they explain vocal effort to their patients. The most common terms were effort/effortful (n=42), work (n=31), hard/harder (n=16), physical (n=9), strain (n=12), muscles (n=10), push/pushing (n=6), tired/tiring (n=7), and force (n=3).

Diagnostic Measures (n=86)

When asked how they measured vocal effort in diagnostics, seventy-eight percent (n=67) reported using the Voice Handicap Index (Jacobson et al., 1997) or VHI-10 (Rosen et al., 2004). Other perceptual scales used included a visual analog scale (n=26), direct magnitude estimation (n=16), the Vocal Fatigue Index (Nanjundeswaran et al., 2015; n=13), Borg scales (n=10), and the Evaluation of the Ability to Sing Easily (Phyland et al., 2014; n=10. See Table 2 for a list of diagnostic procedures.

Table 2.

Diagnostic measures to quantify vocal effort (n=86)

Measure Respondents n % of total
Voice Handicap Index 67 78
Visual Analog Scales 26 30
Direct Magnitude Estimation 16 19
Vocal Fatigue Index 13 15
Evaluation of the Ability to Sing Easily 10 12
Borg scales 10 12
No measures 5 6
Voice Symptom Scale* 3 3
Other 21 24
Open in a new tab

Vocal Effort in Therapy (n=85)

Of 85 respondents, almost half (n=39) reported that they include a reduction of vocal effort in their therapy goals “most of the time”. Another one-fifth of clinicians include this goal “always” (n=17), see Figure 6. Clinicians were asked to describe any specific therapy techniques they have aimed at reducing effort. The most common techniques mentioned were Lessac Madsen Resonant Voice Therapy or resonant voice (Verdolini-Marston et al., 1995; Verdolini, 2000; n=30; ), Semi-Occluded Vocal Tract exercises or straw phonation (Titze, 2006; n=25), Casper Stone Flow Phonation or flow phonation (Stone & Casteel, 1982; n=15), massage (Roy & Bless, 1998; n=11), muscle tension releases and stretches (n=10), breath training (n=10), Vocal Function Exercises (Joseph C. Stemple et al., 1994; n=6), easy onset/easy production (n=6), confidential voice (Casper, 2000; n=3), and stretches (n=4); see Table 3.

Figure 6.

Figure 6.

Open in a new tab

Responses to “How often do you include reduction of vocal effort in your therapy goals?”

Table 3.

Therapy techniques to reduce vocal effort (n=85)

Voice Therapy Technique Respondents n % of total
(Lessac Madsen) Resonant Voice Therapy 30 35
Semi-Occluded Vocal Tract exercises 25 29
Casper-Stone Flow Phonation 15 18
Massage 11 13
Muscle tension release and stretches 10 12
Breath training 10 12
Vocal Function Exercises 6 7
Easy onset 6 7
Confidential Voice 3 4
Open in a new tab

Opinions on Vocal Effort

The survey’s final question asked participants to select all statements about which vocal effort they agreed. Results of the final question are summarized in Table 4.

Table 4.

Participants’ opinions on vocal effort (n=89)

Statement Respondents n % of total
Vocal effort is important to highlight in therapy 79 90
Vocal effort is not important to highlight in therapy 1 1
Vocal effort can be reduced with therapy 87 100
Vocal effort can be increased with therapy 47 53
Patients change their vocal effort perceptions during therapy 77 89
Patients do not change their vocal effort perceptions during therapy 4 5
Vocal effort is dependent physical factors such as height, weight, & sex 8 8
Vocal effort is dependent on age 17 18
Vocal effort is dependent on general wellness and physical fitness 40 46
Vocal effort is dependent on general fatigue 53 61
Vocal effort is dependent on personality, intelligence, and mood 43 51
Open in a new tab

Discussion

Survey results suggest that, from the perspective of the vocal health professionals, vocal effort is a commonly experienced symptom of their patients seeking voice treatment. Although vocal effort is rarely the only symptom reported, most clinicians say that a notable percentage of their caseload present with vocal effort at their main (and sometimes only) symptom. The survey also verifies that clinicians believe vocal effort can be manipulated and is an important therapy goal. Further, most clinicians include vocal effort reduction as a therapy goal for most of their voice patients.

Despite the importance of vocal effort to both patients and clinicians, the survey found that most clinicians used the Voice Handicap Index (VHI) to track effort. Although the VHI does capture some aspects of vocal effort in item 14, “I feel as though I have to strain to produce voice,” and item 20, “I use a great deal of effort to speak”, as well as less direct aspects of effort in item 7 “I am tense when talking to others because of my voice,” these items are only 3 of the 30 items on the full VHI and lack extensive validation that they indeed capture vocal effort. Given the reduced number of items relating to vocal effort and the understanding that the VHI is a measure of perceived handicap and not specifically, perceived effort, it is unlikely that the VHI adequately captures vocal effort. Furthermore, many clinicians reported using the Voice Handicap Index −10 (VHI-10), not the full VHI to capture vocal effort in their patients. However, the VHI-10 only retained item 7 that loosely relates to vocal effort through feelings of tenseness, which infers effort. This is not to say that the VHI and VHI-10 should be eliminated from clinical protocols; however, they were not specifically designed to capture vocal effort.

Far fewer clinicians use the Vocal Fatigue Index (VFI), which captures long-term effects of increased vocal effort. Visual analogue scales, direct magnitude estimation scales, and Borg scales also appeared on the list of measures that clinicians use. These measures, which capture how an individual experiences vocal effort following a vocal task, more accurately capture vocal effort but remain non-standardized and unvalidated. For these measures to be appropriate for capturing vocal effort pre-and post-therapy and to adequately place an individual on a severity scale, inter- and intra-reliability needs to be established for each measure.

Another finding in this survey revealed that clinicians noted many patients have difficulty reporting symptoms of vocal effort. Some of the common words that were used appear to be strain, hard, work, push, tired/tiring, fatigue, effort, exhausting, pain, force, and tight. Knowing that these terms are often used by patients might be important when developing instructions for a vocal effort scale. Furthermore, of the nine most reported words that patients use to describe vocal effort, six of them were also words that clinicians used. These terms may prove useful in developing vocal effort scale anchors or patient instructions.

Despite challenges in measuring vocal effort, clinicians reported multiple techniques to manage vocal effort. Voice therapy techniques of resonant voice therapy, semi-occluded vocal tract therapy, flow phonation, and manual therapies appear to address vocal effort in some way. The wide range of therapy techniques that address all the subsystems of voicing suggests that embedded in our therapy is the notion of a maximal level of vocal effort. In fact, some of these therapies, specifically Lessac Madsen Resonant Voice Therapy (Verdolini-Marston et al., 1995; Verdolini, 2000) and Casper-Stone Flow Phonation (Stone & Casteel, 1982), are based on the tenants of reduced vocal strain for optimal voicing. Given the focus of effort reduction that many of the most popular therapies possess, measuring vocal effort would be paramount in establishing pre-and post-therapy efficacy in this domain.

Given that this symptom is a prevalent and important complaint of patients, it behooves us to develop appropriate measurement tools to quantify this patient-perceived symptom. As reimbursement for services becomes increasingly dependent on patient reported satisfaction with treatment, and because addressing this highly reported symptom should increase satisfaction, quantifying vocal effort will undoubtedly be reflected in therapy improvement and provide clinicians with solid evidence of such improvement. This study reveals the importance of vocal effort for both patients and clinicians and outlines the importance of developing efficient and effective measurement tools to capture effort. Future empirical studies investigate how best to quantify vocal effort which not only is important to establish formal epidemiological data but to provide a powerful therapy efficacy measurement, one that captures the patient’s perspective. Future studies should aim to quantify levels of severity of vocal effort, track changes in vocal effort perception throughout the therapeutic process, and to quantify the changes in quality of life issues surrounding communication.

Learning Outcomes.

  1. Define vocal effort and its relationship to voice disorders.

  2. List the different methods that vocal effort has been measured in the literature.

  3. Explain the importance of developing a reliable and valid measurement tool to assess vocal effort.

Acknowledgements

The authors would like to thank Jeffrey Searl, Sarah Ferguson, Susanna Whitling, Lady Cantor-Captiva, and Mark Berardi for their helpful comments during the development of the survey.

The authors have received no funding for this project.

Footnotes

Conflict of interest: The authors have no conflict of interest regarding this project.

References

  1. Borg E (2007). On perceived exertion and its measurement. In Psychology. 10.1037/e529832013-001 [DOI] [Google Scholar]
  2. Borg G (1982). Psychophysical bases of perceived exertion. Medicine and Science in Sports and Exercise, 14(5), 377–381. [PubMed] [Google Scholar]
  3. Borg G (1990). Psychophysical scaling with applications in physical work and the perception of exertion. Scandinavian Journal of Work, Environment, & Health, 16(1), 55–58. [DOI] [PubMed] [Google Scholar]
  4. Bottalico P (2017). Speech Adjustments for Room Acoustics and Their Effects on Vocal Effort. Journal of Voice, 31(3), e392.1–e392.12. 10.1016/j.jvoice.2016.10.001 [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Bottalico P, Graetzer S, & Hunter EJ (2016a). Effects of speech style, room acoustics, and vocal fatigue on vocal effort. The Journal of the Acoustical Society of America, 139(5), 2870–2879. 10.1121/1.4950812 [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Bottalico P, Graetzer S, & Hunter EJ (2016b). Effects of speech style, room acoustics, and vocal fatigue on vocal effort. The Journal of the Acoustical Society of America. 10.1121/1.4950812 [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Brandt JF, Ruder KF, & Shipp T (1969). Vocal Loudness and Effort in Continuous Speech. The Journal of the Acoustical Society of America, 46(6B), 1543–1548. 10.1121/1.1911899 [DOI] [PubMed] [Google Scholar]
  8. Casper J (2000). Confidential voice. In Stemple Joseph C. (Ed.), Voice therapy: Clinical studies (pp. 128–139). Singular. [Google Scholar]
  9. Chang A, & Karnell MP (2004). Perceived phonatory effort and phonation threshold pressure across a prolonged voice loading task: A study of vocal fatigue. Journal of Voice, 18(4), 454–466. 10.1016/j.jvoice.2004.01.004 [DOI] [PubMed] [Google Scholar]
  10. Colton RH, & Brown WS (1973). Some Relationships between Vocal Effort and Intraoral Air Pressure. The Journal of the Acoustical Society of America, 53(1), 296–296. 10.1121/1.1982186 [DOI] [Google Scholar]
  11. Deary IJ, Wilson JA, Carding PN, & MacKenzie K (2003). VoiSS: A patient-derived Voice Symptom Scale. Journal of Psychosomatic Research, 54(5), 483–489. 10.1016/S0022-3999(02)00469-5 [DOI] [PubMed] [Google Scholar]
  12. Eadie TL, Rajabzadeh R, Isetti DD, Nevdahl MT, & Baylor CR (2017). The effect of information and severity on perception of speakers with adductor spasmodic dysphonia. American Journal of Speech-Language Pathology, 26(2), 327–341. 10.1044/2016_AJSLP-15-0191 [DOI] [PubMed] [Google Scholar]
  13. Eadie TL, & Stepp CE (2013). Acoustic correlate of vocal effort in spasmodic dysphonia. Annals of Otology, Rhinology and Laryngology, 122(3), 169–176. 10.1177/000348941312200305 [DOI] [PubMed] [Google Scholar]
  14. Ford Baldner E, Doll E, & Van Mersbergen MR (2015). A Review of Measures of Vocal Effort With a Preliminary Study on the Establishment of a Vocal Effort Measure. Journal of Voice, 29(5). 10.1016/j.jvoice.2014.08.017 [DOI] [PubMed] [Google Scholar]
  15. Gilman M, & Johns MM (2017). The Effect of Head Position and/or Stance on the Self-perception of Phonatory Effort. Journal of Voice, 31(1), e31.1–e31.4. 10.1016/j.jvoice.2015.11.024 [DOI] [PubMed] [Google Scholar]
  16. Giovanni A, Akl L, & Ouaknine M (2008). Postural dynamics and vocal effort: Preliminary experimental analysis. Folia Phoniatrica et Logopaedica, 60(2), 80–85. 10.1159/000114649 [DOI] [PubMed] [Google Scholar]
  17. Hunter EJ, Cantor-Cutiva LC, van Leer E, van Mersbergen M, Nanjundeswaran CD, Bottalico P, Sandage MJ, & Whitling S (2020). Toward a consensus description of vocal effort, vocal load, vocal loading, and vocal fatigue. In Journal of Speech, Language, and Hearing Research. 10.1044/2019_JSLHR-19-00057 [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Isetti D, Xuereb L, & Eadie TL (2014). Inferring speaker attributes in adductor spasmodic dysphonia: Ratings from unfamiliar listeners. American Journal of Speech-Language Pathology, 23(2), 134–145. 10.1044/2013_AJSLP-13-0010 [DOI] [PubMed] [Google Scholar]
  19. Jacobson BH, Johnson A, Grywalski C, Silbergleit A, Jacobson G, Benninger MS, & Newman CW (1997). The Voice Handicap Index (VHI): Development and Validation. American Journal of Speech-Language Pathology, 6(3), 66–70. 10.1044/1058-0360.0603.66 [DOI] [Google Scholar]
  20. Johnson JR, & Eadie T (2012). A Comparison Between Self-Rated and Listener-Rated Outcomes in Tracheoesophageal Speech. In ProQuest Dissertations and Theses. University of Washington. [Google Scholar]
  21. Lagier A, Vaugoyeau M, Ghio A, Legou T, Giovanni A, & Assaiante C (2010). Coordination between posture and phonation in vocal effort behavior. Folia Phoniatrica et Logopaedica, 62(4), 195–202. 10.1159/000314264 [DOI] [PubMed] [Google Scholar]
  22. Leeper HA, & Noll JD (1972). Pressure Measurements of Articulatory Behavior during Alterations of Vocal Effort. Journal of the Acoustical Society of America, 51(4B), 1291*1295. 10.1121/1.1912973 [DOI] [PubMed] [Google Scholar]
  23. Liénard J-S, & Di Benedetto M-G (1999). Effect of vocal effort on spectral properties of vowels. The Journal of the Acoustical Society of America, 106(1), 411–422. 10.1121/1.428140 [DOI] [PubMed] [Google Scholar]
  24. McKenna VS, & Stepp CE (2018). The relationship between acoustical and perceptual measures of vocal effort. The Journal of the Acoustical Society of America, 144(3), 1643–1658. 10.1121/1.5055234 [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Nanjundeswaran C, Jacobson BH, Gartner-Schmidt J, & Verdolini Abbott K (2015). Vocal Fatigue Index (VFI): Development and Validation. Journal of Voice, 29(4), 433–440. 10.1016/j.jvoice.2014.09.012 [DOI] [PubMed] [Google Scholar]
  26. Pageaux B (2016). Perception of effort in Exercise Science: Definition, measurement and perspectives. In European Journal of Sport Science. 10.1080/17461391.2016.1188992 [DOI] [PubMed] [Google Scholar]
  27. Phyland DJ, Pallant JF, Thibeault SL, Benninger MS, Vallance N, & Smith JA (2014). Measuring vocal function in professional music theater singers: Construct validation of the evaluation of the ability to sing easily (EASE). Folia Phoniatrica et Logopaedica, 66(3), 100–108. 10.1159/000366202 [DOI] [PubMed] [Google Scholar]
  28. Razon S, Hutchinson J, & Tenenbaum G (2020). Effort Perception. In Measurement in Sport and Exercise Psychology. 10.5040/9781492596332.ch-024 [DOI] [Google Scholar]
  29. Rosen CA, Lee AS, Osborne J, Zullo T, & Murry T (2004). Development and validation of the voice handicap index-10. Laryngoscope, 114(9), 1549–1556. 10.1097/00005537-200409000-00009 [DOI] [PubMed] [Google Scholar]
  30. Rosenthal AL, Lowell SY, & Colton RH (2014). Aerodynamic and acoustic features of vocal effort. Journal of Voice. 10.1016/j.jvoice.2013.09.007 [DOI] [PubMed] [Google Scholar]
  31. Roy N, & Bless DM (1998). Manual circumlaryngeal techniques in the assessment and treatment of voice disorders. In Current Opinion in Otolaryngology and Head and Neck Surgery. 10.1097/00020840-199806000-00002 [DOI] [Google Scholar]
  32. Sampaio MC, Borges Dos Reis EJF, Carvalho FM, Porto LA, & Araújo TM (2012). Vocal effort and voice handicap among teachers. Journal of Voice, 26(6), e820.15–e820.18. 10.1016/j.jvoice.2012.06.003 [DOI] [PubMed] [Google Scholar]
  33. Searl J, & Knollhoff S (2018). Sense of effort and fatigue associated with talking after total laryngectomy. American Journal of Speech-Language Pathology, 27(4), 1434–1444. 10.1044/2018_AJSLP-17-0218 [DOI] [PubMed] [Google Scholar]
  34. Shoffel-Havakuk H, Marks KL, Morton M, Johns MM, & Hapner ER (2019). Validation of the OMNI vocal effort scale in the treatment of adductor spasmodic dysphonia. Laryngoscope, 129(2), 448–453. 10.1002/lary.27430 [DOI] [PubMed] [Google Scholar]
  35. Solomon NP, Glaze LE, Arnold RR, & Van Mersbergen M (2003). Effects of a vocally fatiguing task and systemic hydration on men’s voices. Journal of Voice, 17(1). 10.1016/S0892-1997(03)00029-8 [DOI] [PubMed] [Google Scholar]
  36. Solomon Nancy Pearl. (2008a). Vocal fatigue and its relation to vocal hyperfunction. In International Journal of Speech-Language Pathology. 10.1080/14417040701730990 [DOI] [PubMed] [Google Scholar]
  37. Solomon Nancy Pearl. (2008b). Vocal fatigue and its relation to vocal hyperfunction. International Journal of Speech-Language Pathology, 10(4), 254–266. 10.1080/14417040701730990 [DOI] [PubMed] [Google Scholar]
  38. Stemple Joseph C., Lee L, D’Amico B, & Pickup B. (1994). Efficacy of vocal function exercises as a method of improving voice production. Journal of Voice, 8(2), 271–278. 10.1016/S0892-1997(05)80299-1 [DOI] [PubMed] [Google Scholar]
  39. Stevens SS (1958). Problems and methods of psychophysics. Psychological Bulletin, 55(4), 177–196. 10.1037/h0044251 [DOI] [PubMed] [Google Scholar]
  40. Stevens SS (1971). Issues in psychophysical measurement. Psychological Review, 78(5), 426–450. 10.1037/h0031324 [DOI] [Google Scholar]
  41. Stone RE, & Casteel R (1982). Restoration of voice in nonorganically based dysphonia. In Filter M (Ed.), Phonatory voice disorders in children (pp. 132–165). C.C. Thomas. [Google Scholar]
  42. Tenenbaum G, & Eklund RC (Robert C (2007). A social-cognitive perspective of perceived exertion. In Handbook of sport psychology. 3rd ed. (pp. 560–577). [Google Scholar]
  43. Thurstone LL (2017). Psychophysical analysis. In Scaling: A Sourcebook for Behavioral Scientists (pp. 59–80). 10.4324/9781315128948-6 [DOI] [Google Scholar]
  44. Titze IR (2006). Voice training and therapy with a semi-occluded vocal tract: Rationale and scientific underpinnings. Journal of Speech, Language, and Hearing Research, 49, 448–459. 10.1044/1092-4388(2006/035) [DOI] [PubMed] [Google Scholar]
  45. van Leer E, & van Mersbergen M (2017). Using the Borg CR10 Physical Exertion Scale to Measure Patient-perceived Vocal Effort Pre and Post Treatment. Journal of Voice, 31(3), 389.e19–389.e25. 10.1016/j.jvoice.2016.09.023 [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. Van Mersbergen M, & Delany M (2014). Vocal responses to emotional picture viewing. Logopedics Phoniatrics Vocology, 39(3). 10.3109/14015439.2013.777108 [DOI] [PubMed] [Google Scholar]
  47. Van Mersbergen M, Patrick C, & Glaze L (2008). Functional dysphonia during mental imagery: Testing the trait theory of voice disorders. Journal of Speech, Language, and Hearing Research, 51(6). 10.1044/1092-4388(2008/06-0216) [DOI] [PubMed] [Google Scholar]
  48. van Mersbergen Miriam, Lyons P, & Riegler D (2017). Vocal responses in heighted states of arousal. Journal of Voice, 31(1), 127.e13–127.e19. 10.1016/j.jvoice.2015.12.011 [DOI] [PubMed] [Google Scholar]
  49. van Mersbergen Miriam, Vinney LA, & Payne AE. (2019). Cognitive influences on perceived phonatory exertion using the Borg CR10. Logopedics Phoniatrics Vocology. 10.1080/14015439.2019.1617895 [DOI] [PubMed] [Google Scholar]
  50. Verdolini-Marston K, Katherine Burke M, Lessac A, Glaze L, & Caldwell E (1995). Preliminary study of two methods of treatment for laryngeal nodules. Journal of Voice, 9(1), 74–85. 10.1016/S0892-1997(05)80225-5 [DOI] [PubMed] [Google Scholar]
  51. Verdolini K (2000). Resonant Voice Therapy. In Stemple JC (Ed.), Voice therapy: Clinical studies (pp. 46–61). Singular. [Google Scholar]
  52. Vinney LA, van Mersbergen M, Connor NP, & Turkstra LS (2016). Vocal Control: Is It Susceptible to the Negative Effects of Self-Regulatory Depletion? Journal of Voice, 30(5). 10.1016/j.jvoice.2015.07.016 [DOI] [PubMed] [Google Scholar]

RESOURCES