Effects of speech style, room acoustics, and vocal fatigue on vocal effort

Cognitive load associated with speaking clearly in reverberant rooms

Communication is a fundamental aspect of human interaction, yet many individuals must speak in less-than-ideal acoustic environments daily. Adapting their speech to ensure intelligibility in these varied settings can impose a significant cognitive burden. Understanding this burden on talkers has significant implications for the design of public spaces and workplace environments, as well as speaker training programs. The aim of this study was to examine how room acoustics and speaking style affect cognitive load through self-rating of mental demand and pupillometry. Nineteen adult native speakers of American English were instructed to read sentences in both casual and clear speech-a technique known to enhance intelligibility-across three levels of reverberation (0.05 s, 1.2 s, and 1.83 s at 500-1000 Hz). Our findings revealed that speaking style consistently affects the cognitive load on talkers more than room acoustics across the tested reverberation range. Specifically, pupillometry data suggested that speaking in clear speech elevates the cognitive load comparably to speaking in a room with long reverberation, challenging the conventional view of clear speech as an 'easy' strategy for improving intelligibility. These results underscore the importance of accounting for talkers' cognitive load when optimizing room acoustics and developing speech production training.

A Semiautomated Protocol Towards Quantifying Vocal Effort in Relation to Vocal Performance During a Vocal Loading Task

To increase the reliability and comparability of vocal loading studies, this paper proposes the use of a standardized approach with experiments that are [1] grounded on consistent definitions of terms related to vocal fatigue (vocal effort, vocal demand, and vocal demand response), and [2] designed to reduce uncertainty and increase repeatability. In the approach, a semi-automated vocal loading task that also increases efficiencies in collecting and preparing vocal samples for analysis was used to answer the following research question: To what extent is vocal effort and vocal demand response sensitive to changes in vocal demands (ie, noise only, noise plus duration)? Results indicate that the proposed protocol design consistently induced change in both vocal effort and vocal demand response, indicating vocal fatigue. The efficacy of future vocal loading studies would be improved by adopting a more consistent methodology for quantifying vocal fatigue, thus increasing interstudy comparability of results and conclusions.

The Impact of a Vocal Loading Task on Voice Characteristics of Female Speakers With Benign Vocal Fold Lesions

OBJECTIVES

To examine the effect of a vocal loading task on measures of vocal structure and function in females with benign vocal fold lesions (BVFLs) and determine if change is observed in voice and lesion characteristics.

STUDY DESIGN

Prospective cohort study.

METHODS

Twenty-eight (n = 28) female subjects with phonotraumatic BVFLs completed a vocal loading task of 30 minutes of reading aloud at 75-85 dBA. Multidimensional voice evaluation was completed pre- and post-load, including audio and videostroboscopy recordings and images for expert perceptual ratings and acoustic and aerodynamic evaluation. Subjects also scored themselves using a 10 cm visual analogue scale for Perceived Phonatory Effort, and completed the Evaluation of Ability to Voice Easily, a 12 item self-report scale of current perceived speaking voice function. An exploratory rather than confirmatory approach to data analysis was adopted. The direction and magnitude of the change scores (pre- to post-load) for each individual, across a wide variety of instrumental and self-report measures, were assessed against a Minimal Clinically Important Difference criteria.

RESULTS

Observations of change and the direction of change in vocal response of individuals with BVFLs to 30 minutes of loud vocal load was variable. Minimal to no change was noted for participants pre- to post-load as rated perceptually, for auditory and videostroboscopy samples. For most instrumental measures, change was shown for many participants including an overall improvement in aerodynamic and acoustic measures of function and efficiency post-load for 20 participants (77%) and decline in function for 4 participants (15%). Self-reported effort and vocal function post-load was multidirectional with similar numbers of participants reporting no change, improved function or a decline.

CONCLUSION

Subjects with BVFLs demonstrate change in vocal function following 30 minutes of vocal load. While this change can be variable and multidirectional, overall improvement was observed in instrumental measures of function and efficiency for most participants. Some participants perceived this change to be an increase in effort, some a reduction in effort and some perceived no change. Improved vocal function despite relative lesion stability can seemingly occur after loading in some pathological voices.

Measuring Vocal Fatigability in Teachers: The Vocal Fatigability Scale for Teachers (VFS-T)

OBJECTIVES

This study focuses on the distinction between vocal fatigability and vocal fatigue (VF), highlighting the importance of vocal fatigability when assessing teachers' quality of life. Vocal fatigability is more critical for quality of life than performance or perceived VF because it considers the accumulation and chronicity of fatigue over isolated tasks. The objectives are to develop and validate the Vocal Fatigability Scale for Teachers (VFS-T), to assess teachers' levels of vocal fatigability, and to analyze variations based on personal and occupational traits. The VFS-T construct encompasses items related to vocal sensations and performance, their connection to accumulated demanding vocal activity, descriptions of recovery strategies, necessary rest periods, and the impact of VF on daily activities.

STUDY DESIGN

A single cross-sectional study with an ex post facto design was conducted.

METHODS

The sample consisted of 184 active teachers with various vocal conditions. They completed the VFS-T questionnaire, provided personal and occupational data, and completed the VHI-10 questionnaire. The data collected were analyzed for item refinement, internal structure, reliability, validity, diagnostic capacity, cutoff values, and group differences.

RESULTS

The item refinement and internal structure analysis revealed a scale comprising 17 items grouped into two factors. The VFS-T shows good reliability and validity, with cutoffs at <15 for no fatigability, 15-27 for moderate fatigability, and >28 for high fatigability. Most teachers fall into the moderate fatigability range, with 72% experiencing vocal fatigability.

CONCLUSIONS

The VFS-T is a reliable tool for detecting vocal fatigability in teachers. This scale focuses on the construct of vocal fatigability, which is related to chronicity of VF and limitations in daily activities in teachers.

Concentration of reflected sound in a room treated with cube corner retroreflectorsa)

A room was treated to be predominantly retroreflective in the high frequency range by introducing arrays of cube corner retroreflectors (CCRs) over most surfaces (excluding the floor). In a small room (volume 55 m3), 156 CCRs in the form of square trihedra with 350 mm edge lengths were used as wall and ceiling treatment. The horizontal plane distribution of reflected energy was measured from omnidirectional sources, and a head and torso simulator was used to measure voice support. Results show a high concentration of reflected energy returned to omnidirectional source positions in high frequency octave bands (2-8 kHz). Finite-difference time-domain (FDTD) simulations of the room yielded similar distributions to the omnidirectional measurements, showing greater sound concentration when more CCRs are introduced. By contrast, FDTD simulation of an equivalent flat-surfaced room yielded no reflected sound concentration at the source, with results close to diffuse field theory in high frequency octave bands. Measured voice support values derived from oral-binaural room impulse responses exceed diffuse theory expectations by 5 dB. Thus, the paper demonstrates that retroreflective array treatment can change room acoustical conditions, concentrating reflected energy onto an arbitrarily located source.

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.

The Effects of Reading Speed on Acoustic Voice Parameters and Self-reported Vocal Fatigue in Students

INTRODUCTION

Vocal loading tasks (VLTs) help researchers gather acoustic measurements and understand how a healthy speaker adjusts their voice in response to challenges. There is a dearth of evidence measuring the impact of speaking rate in VLTs on acoustic voice parameters and vocal fatigue.

OBJECTIVES

In the present study, the relationships between acoustic voice parameters and self-reported vocal fatigue were examined through an experimental VLT.

METHODS

38 students completed a 45-minute VLT which involved the recording of three randomized reading tasks. The tasks varied by the speed in which the words were presented (slow, medium, fast) on a computer monitor. Vocal fatigue ratings were measured subjectively using a Borg scale and negative adaptations to vocal loading were measured objectively using Sound Pressure Level (SPL, in dBA), fundamental frequency (fo, in semitones), and phonation time (Dt %).

RESULTS

Analysis indicated that vocal fatigue increases with time, and the slope of this relationship is affected by the speaking rate. SPL and fo increased with speaking rate and the standard deviation of SPL and fo decreased with speaking rate. On average, the male participants' phonation time values were 7.8% lower than the female participants. The rate of increase of vocal fatigue with time during the experiment was higher in the fast speaking style compared to the slow and medium ones.

CONCLUSION

The results provide support that the novel VLT altered multiple vocal parameters to induce measurable changes in vocal fatigue.

Effects of warm-up exercises on self-assessed vocal effort

PURPOSE

An elevated sense of vocal effort due to increased vocal demand is frequently reported by patients with voice disorders. However, effects of vocal warm-up on self-assessed vocal effort have not been thoroughly examined. A recently developed version of the Borg CR-10 Scale facilitates vocal effort assessments, following different vocal warm-up tasks.

METHODS

Effects of a short (5 min) vocal warm-up on self-assessed vocal effort was evaluated using the Borg CR-10. Twenty-six vocally healthy participants (13F, 13M, mean age 22.6), in two randomised groups, underwent sessions of either reading aloud or semi-occluded vocal tract exercises (SOVTE). Vocal effort was evaluated at four times: pre to post vocal warm-up and two silence periods. Non-parametric analyses for repeated measures and calculations for within-subject standard deviation were applied in group comparisons.

RESULTS

Following vocal warm-up, vocal effort ratings were increased to a statistically significant degree in both intervention groups compared to baseline ratings. After a 5-min rest in silence following completion of the vocal warm-up, vocal effort ratings returned to baseline levels in both groups. The drop in ratings immediately post warm-up compared to 5 min later was statistically significant for the SOVTE group.

CONCLUSIONS

Five minutes of vocal warm-up caused increased self-perceived vocal effort in vocally healthy individuals. The increased sense of effort dissipated faster following warm-up for the SOVTE group. When using the Borg CR-10 scale to track vocal effort, it may be beneficial to apply experience-based anchors.

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.

Association Between Bilingualism, Vocal Effort, and Background Noise With Voice Fundamental Frequency and LTAS Among Spanish-English Bilingual Teachers

BACKGROUND

As the world becomes increasingly interconnected, the demand for bilingual teachers has grown exponentially. However, the unique combination of being a bilingual occupational voice user establishes challenges that warrant careful examination.

OBJECTIVE

To investigate the association between bilingualism, vocal effort, and background noise with fundamental frequency and long-term spectrum average among Spanish-English bilingual teachers.

METHODS

Exploratory cross-sectional correlational study with the participation of eight Spanish-English proficient bilingual teachers (native Spanish speakers) who were teaching online classes during the quarantines established to mitigate the propagation of COVID-19. Participants were asked to read two standardized texts (one in English and one in Spanish) under two background noise conditions (with and without background white noise).

RESULTS

There was a significant interaction between language and vocal effort considering that the association of vocal effort with fo was different for Spanish and English. There was also a significant main effect of background noise on fo. There were significant differences in voice spectral characteristics between productions in Spanish and English and between productions with and without background noise. The alpha ratio was significantly higher in productions in English and with background noise compared with productions in Spanish without background noise. The mid to high spectral energy ratio (1-5 K/5-8 K) was significantly lower in productions in English and with higher perceived vocal effort compared with productions in Spanish and with lower scores on the Borg Scale.

CONCLUSION

Our findings introduce a need perspective by emphasizing the impact of speaking a second language on the work-relatedness of voice disorders among teachers. These findings stress the necessity to factor in language and environmental conditions for the comprehensive evaluation and management of work-related voice disorders.

Singing in different performance spaces: The effect of room acoustics on singers' perception

Classical singers' performances vary across different acoustic environments. The changes in the delivery are influenced by the singer's perception of the venue's acoustics. This study investigated these relationships using nine professional or semi-professional classical singers. Participants performed Giordani's "Caro mio ben" aria in five venues, and the acoustic parameters reverberance (T30 and EDT), clarity (C80), early vocal support (STv), and tonal color (EDTf) were measured. From a factor analysis of the subjective analysis three major factors emerged that, we propose, would represent three generalized percepts of Room Supportiveness, Room Noiselessness, and Room Timbre. These percepts correlated significantly with objective acoustic parameters traditionally linked to vocal support, reverberation, and timbre. Room Supportiveness and Room Noiselessness significantly contributed to the singers' likability of the acoustic environment, while Room Timbre did not. This indicates that singers' perceptual preference for a performance space may be influenced by factors affecting both auditory feedback and vocal function. These findings underscore the need for performing space designers to consider the unique needs of all stakeholders, including listeners and performers. The study contributes to the bridging of the gap between subjective perceptions and objective measurements, providing valuable insights for acoustic design considerations.

The Influence of Multisensory Input On Voice Perception and Production Using Immersive Virtual Reality

OBJECTIVES

The purpose was to examine the influence of auditory vs visual vs combined audiovisual input on perception and production of one's own voice, using immersive virtual reality technology.

METHODS

Thirty-one vocally healthy men and women were investigated under 18 sensory input conditions, using immersive virtual reality technology. Conditions included two auditory rooms with varying reverberation times, two visual rooms with varying volumes, and the combination of audiovisual conditions. All conditions were repeated with and without background noise. Speech tasks included counting, sustained vowel phonation, an all-voiced sentence from the Consensus Auditory-Perceptual Evaluation of Voice, and the first sentence from the Rainbow Passage, randomly ordered. Perception outcome measures were participants' self-reported perceptions of their vocal loudness, vocal effort, and vocal comfort in speech. Production outcome measures were sound pressure level (SPL) and spectral moments (spectral mean and standard deviation in Hz, skewness, and kurtosis). Statistical analyses used self-reported vocal effort, vocal loudness, and vocal comfort in percent (0 = "not at all," 100 = extremely), SPL in dB, and spectral moments in Hz. The reference level was a baseline audiovisual deprivation condition.

RESULTS

Results suggested (i) increased self-perceived vocal loudness and effort, and decreased comfort, with increasing room volume, speaker-to-listener distance, audiovisual input, and background noise, and (ii) increased SPL and fluctuations in spectral moments across conditions.

CONCLUSIONS

Not only auditory, but also visual and audiovisual input influenced voice perception and production in ways that have not been previously documented. Findings contribute to the basic science understanding the role of visual, audiovisual and auditory input in voice perception and production, and also to models of voice training and therapy. The findings also set the foundation for the use of virtual reality in voice and speech training, as a potentially power solution to the generalization problem.

Work-Related Vocal Challenges of Online Teaching: A Study of Female College Professors

BACKGROUND

College professors are at an elevated risk of developing voice disorders due to increased vocal demands associated with their working conditions, including high background noise levels, long reverberation times, prolonged voice use duration, and large class sizes. However, the impact of online classes on vocal health among college professors remains unclear.

OBJECTIVE

This longitudinal study aimed to characterize voice changes associated with online teaching among female Colombian college professors.

METHODS

Thirteen female college professors teaching online classes completed an online survey that included questions about voice functioning, working conditions, the Spanish translation of the Vocal Fatigue Index (VFI), and the Spanish translation of the Voice-Related Quality of Life. Instrumental measurements were also performed, including environmental background noise levels, hearing screening, and voice recordings before and after a synchronous online class.

RESULTS

This study found a decreased fundamental frequency in connected speech (reading) associated with the number of students per class, the number of classes per week, and background noise levels measured with a sound level meter. L1L0 was statistically smaller among experienced teachers with higher background noise levels compared with less-experienced colleagues in quieter classes. 1558kHz was statistically associated with the average number of students, whereas HNR was slightly higher for professors with more students and more classes per week.

CONCLUSION

The findings suggest that online teaching has important implications for voice production among participating teachers. This study highlights the importance of considering working conditions during online classes when designing workplace prevention programs for college professors.

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.

Speaking in the presence of noise: Consistency of acoustic properties in clear-Lombard speech over time

Individual speakers are often able to modify their speech to facilitate communication in challenging conditions, such as speaking in a noisy environment. Such vocal "enrichments" might include reductions in speech rate or increases in acoustic contrasts. However, it is unclear how consistently speakers enrich their speech over time. This study examined inter-speaker variability in the speech enrichment modifications applied by speakers. The study compared a baseline habitual speaking style to a clear-Lombard style and measured changes in acoustic differences between the two styles over sentence trials. Seventy-eight young adult participants read out sentences in the habitual and clear-Lombard speaking styles. Acoustic differences between speaking styles generally increased nonlinearly over trials, suggesting that speakers require practice before realizing their full speech enrichment potential when speaking clearly in noise with reduced auditory feedback. Using a recent objective intelligibility metric based on glimpses, the study also found that predicted intelligibility increased over trials, highlighting that communicative benefits of the clear-Lombard style are not static. These findings underline the dynamic nature of speaking styles.

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.

Are Occupational Voice Disorders Accurately Measured? A Systematic Review of Prevalence and Methodologies in Schoolteachers to Report Voice Disorders

PURPOSE

Different measuring instruments have been described to determine the prevalence of voice disorders in schoolteachers. However, the heterogeneity of prevalence figures has made it difficult in determining the impact of voice disorders in this group. This investigation aims to review and identify scientific evidence of methodological analysis of voice disorders in teachers, the relevance of measuring instruments, the prevalence of dysphonia, and the impact on the development of vocal health prevention programs.

METHODS

A systematic review was conducted by searching six important scientific databases. Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines were carried out. Articles were included whether they presented data related to the prevalence of dysphonia and the impact of therapy programs on teachers.

RESULTS

Twenty articles out of 8,998 were selected. The cross-sectional design type was predominant throughout the investigations. Differences were observed in the number of participants across studies, leading to heterogeneous prevalence figures - which ranged from 10.5% to 69.1%. The assessment instruments are not standardly used to effectively determine the disease burden. Despite the fact of the extensive evidence of the effectiveness of programs that address dysphonia in teachers, the scarcity of literature is yet evident on systematic programs promoted by either the government or educational institutions.

CONCLUSION

Findings suggest that future investigations should consider the consensus of a global definition for occupational dysphonia in teachers in order to develop accurately measuring instruments and to assist with voice care programs and treatment approaches in this population. This might be crucial since it could also assist with the implementation of Delphi-type studies that could support the development of further evidence-based agreements around these programs (voice care and treatment approaches) in schoolteachers.

Voice Biofeedback via Bone Conduction Headphones: Effects on Acoustic Voice Parameters and Self-Reported Vocal Effort in Individuals With Voice Disorders

PURPOSE

This study explores sidetone amplification (amplified playback of one's own voice) provided via bone conduction in participants with voice disorders. The effects of bone conduction feedback on acoustic voice parameters and vocal effort ratings are examined.

METHODS

Speech samples of 47 participants with voice disorders were recorded in three auditory feedback conditions: two with sidetone amplification delivered via bone conduction and one condition with no alteration of the feedback. After each task, the participants rated their vocal effort on a visual analog scale. The voice recordings were evaluated by a speech-language pathologist through the GRBAS scale and processed to calculate the within-participant centered sound pressure level (SPL) values, the mean pitch strength (PS), the time dose (Dt%), and cepstral peak prominence smoothed (CPPS). The effects of the feedback conditions on these acoustic parameters and vocal effort ratings were analyzed.

RESULTS

The high sidetone amplification condition resulted in a statistically significant decrease in the within-participant centered SPL values and mean pitch strength across all participants. The feedback conditions had no statistically significant effects on the vocal effort ratings, time dose (Dt%), or CPPS.

CONCLUSIONS

This study provides an evidence that bone conduction sidetone amplification contributes to a consistent adaptation in the within-participant centered SPL values (ΔSPL) in patients with vocal hyperfunction, glottal insufficiency, and organic/neurological laryngeal pathologies compared to conditions with no feedback.

Effects of Virtual Instruction on Educators' Voices During the COVID-19 Pandemic

INTRODUCTION

Resulting from the COVID-19 pandemic, professionals in the United States were mandated to work virtually from home to protect the health needs of the population. The shift in setting and ergonomic factors posed a threat to the vocal health of workers, and more specifically, to those whose professions inflict significant vocal load, such as educators. This study compared the symptoms of vocal tract discomfort and self-perceived voice handicap in full-time educators between face-to-face and virtual settings. Additionally, this study sought to identify relationships between specific environmental factors and levels of discomfort.

METHODS

A cross-sectional research study was conducted by distributing an online survey to 223 individuals who identified as full-time educators. This survey collected data on vocal tract symptoms during both face-to-face and virtual instruction, environmental factors of virtual work setting, personal vocal health habits, and self-perceived voice handicap in each setting.

RESULTS

In this sample population, the shift to a virtual work setting did not result in a significant increase in the number of vocal discomfort symptoms or an increase in vocal handicap. However, environmental factors such as air quality and water intake had the strongest correlation with levels of vocal tract discomfort.

CONCLUSION

It is beneficial to provide resources to full-time educators regarding the risk of voice disorders and the impact of environmental factors on vocal health.

Speaking with a KN95 face mask: a within-subjects study on speaker adaptation and strategies to improve intelligibility

Mask-wearing during the COVID-19 pandemic has prompted a growing interest in the functional impact of masks on speech and communication. Prior work has shown that masks dampen sound, impede visual communication cues, and reduce intelligibility. However, more work is needed to understand how speakers change their speech while wearing a mask and to identify strategies to overcome the impact of wearing a mask. Data were collected from 19 healthy adults during a single in-person session. We investigated the effects of wearing a KN95 mask on speech intelligibility, as judged by two speech-language pathologists, examined speech kinematics and acoustics associated with mask-wearing, and explored KN95 acoustic filtering. We then considered the efficacy of three speaking strategies to improve speech intelligibility: Loud, Clear, and Slow speech. To inform speaker strategy recommendations, we related findings to self-reported speaker effort. Results indicated that healthy speakers could compensate for the presence of a mask and achieve normal speech intelligibility. Additionally, we showed that speaking loudly or clearly-and, to a lesser extent, slowly-improved speech intelligibility. However, using these strategies may require increased physical and cognitive effort and should be used only when necessary. These results can inform recommendations for speakers wearing masks, particularly those with communication disorders (e.g., dysarthria) who may struggle to adapt to a mask but can respond to explicit instructions. Such recommendations may further help non-native speakers and those communicating in a noisy environment or with listeners with hearing loss.

The effects of vocal exertion on lung volume measurements and acoustics in speakers reporting high and low vocal fatigue

Purpose

Vocal exertion is common and often results in reduced respiratory and laryngeal efficiency. It is unknown, however, whether the respiratory kinematic and acoustic adjustments employed during vocal exertion differ between speakers reporting vocal fatigue and those who do not. This study compared respiratory kinematics and acoustic measures in individuals reporting low and high levels of vocal fatigue during a vocal exertion task.

Methods

Individuals reporting low (N = 20) and high (N = 10) vocal fatigue participated in a repeated measures design study over 2 days. On each day, participants completed a 10-minute vocal exertion task consisting of repeated, loud vowel productions at elevated F0 sustained for maximum phonation time. Respiratory kinematic and acoustic measures were analyzed on the 1^st vowel production (T0), and the vowels produced 2 minutes (T2), 5 minutes (T5), 7 minutes (T7), and 10 minutes (T10) into the vocal exertion task. Vowel durations were also measured at each time point.

Results

No differences in respiratory kinematics were observed between low and high vocal fatigue groups at T0. As the vocal exertion task progressed (T2-T10), individuals reporting high vocal fatigue initiated phonation at lower lung volumes while individuals with low vocal fatigue initiated phonation at higher lung volumes. As the exertion task progressed, total lung volume excursion decreased in both groups. Differences in acoustic measures were observed, as individuals reporting high vocal fatigue produced softer, shorter vowels from T0 through T10.

Conclusions

Individuals reporting high vocal fatigue employed less efficient respiratory strategies during periods of increased vocal demand when compared with individuals reporting low vocal fatigue. Individuals reporting high vocal fatigue had shorter maximum phonation time on loud vowels. Further study should examine the potential screening value of loud maximum phonation time, as well as the clinical implications of the observed respiratory patterns for managing vocal fatigue.

Impact of Face Masks on Speech Acoustics and Vocal Effort in Healthcare Professionals

OBJECTIVES/HYPOTHESIS

We investigated speech acoustics and self-reported vocal symptoms in mask-wearing healthcare professionals. We hypothesized that there would be an attenuation of spectral energies and increase in vocal effort during masked speech compared to unmasked speech.

STUDY DESIGN

Within and between subject quasi-experimental design.

METHODS

We prospectively enrolled 21 healthcare providers (13 cisgender female, 8 cisgender male; M = 32.9 years; SD = 7.9 years) and assessed acoustics and perceptual measures with and without a face mask in place. Measurements included: 1) acoustic Vowel Articulation Index (VAI); 2) cepstral and spectral acoustic measures; 3) traditional vocal measures (e.g., fundamental frequency, intensity); 4) relative fundamental frequency (RFF); and 5) self-reported ratings of vocal effort and dyspnea.

RESULTS

During masked speech, there was a significant reduction in VAI, high-frequency information (>4 kHz), and RFF offset 10, as well as a significant increase in cepstral peak prominence and perceived vocal effort. Further analysis showed that high-frequency attenuation was more pronounced when wearing an N95 mask compared to a simple mask.

CONCLUSIONS

Face masks pose an additional barrier to effective communication that primarily impacts spectral characteristics, vowel space measures, and vocal effort. Future work should evaluate how long-term mask use impacts vocal health and may contribute to vocal problems.

LEVEL OF EVIDENCE

3 Laryngoscope, 132:391-397, 2022.

Effect of voice support level and spectrum on conversational speech

One's own voice (autophony) is transmitted to the ears as direct airborne sound, bone conduction, and indirect airborne sound from reflections characterized by overall gain and spectro-temporal features. This study investigates how the spectral profile and gain of simulated indirect airborne sound, quantified as voice support (ST_V), affect the speaking voice of talkers. Pairs of participants performed a conversation elicitation task in anechoic conditions. The indirect airborne sound was provided in real-time via open headphones that maintain the direct airborne transmission path. Experimental conditions included high-pass, low-pass, and all-pass versions of ST_V, each presented at three overall gains, and a Baseline condition with no electroacoustic contribution to ST_V. The results show an overall speech level reduction of 0.22 dB for every additional dB of speech-weighted ST_V, i.e., a -0.22 dB/dB slope. There was some effect of ST_V spectrum on speech: slope for the high-pass condition was steeper (statistically significant) and significantly different from the all-pass slope; spectral balance (2-4 kHz vs 0-2 kHz) of speech showed an interaction effect between gender and experimental conditions. This paper's findings may inform acoustic treatments in environments where overall sound reduction is of interest for favorable ergonomics and occupational health for voice professionals.

Speech and noise levels measured in occupied K-12 classrooms

This project acquired sound levels logged across six school days and impulse responses in 220 classrooms across four K-12 grades. Seventy-four percent met reverberation time recommendations. Sound levels were processed to estimate occupied signal-to-noise ratios (SNRs), using Gaussian mixture modeling and from daily equivalent and statistical levels. A third method, k-means clustering, estimated SNR more precisely, separating data on nine dimensions into one group with high levels across speech frequencies and one without. The SNRs calculated as the daily difference between the average levels for the speech and non-speech clusters are found to be lower than 15 dB in 27.3% of the classrooms and differ from using the other two methods. The k-means data additionally indicate that speech occurred 30.5%-81.2% of the day, with statistically larger percentages found in grade 3 compared to higher grades. Speech levels exceeded 65 dBA 35% of the day, and non-speech levels exceeded 50 dBA 32% of the day, on average, with grades 3 and 8 experiencing speech levels exceeding 65 dBA statistically more often than the other two grades. Finally, classroom speech and non-speech levels were significantly correlated, with a 0.29 dBA increase in speech levels for every 1 dBA in non-speech levels.

Relationship Between Tasked Vocal Effort Levels and Measures of Vocal Intensity

Purpose Patients with voice problems commonly report increased vocal effort, regardless of the underlying pathophysiology. Previous studies investigating vocal effort and voice production have used a range of methods to quantify vocal effort. The goals of the current study were to use the Borg CR100 effort scale to (a) demonstrate the relation between vocal intensity or vocal level (dB) and tasked vocal effort goals and (b) investigate the repeated measure reliability of vocal level at tasked effort level goals. Method Three types of speech (automatic, read, and structured spontaneous) were elicited at four vocal effort level goals on the Borg CR100 scale (2, 13, 25, and 50) from 20 participants (10 females and 10 males). Results Participants' vocal level reliably changed approximately 5 dB between the elicited effort level goals; this difference was statistically significant and repeatable. Biological females produced a voice with consistently less intensity for a vocal effort level goal compared to biological males. Conclusions The results indicate the utility of the Borg CR100 in tracking effort in voice production that is repeatable with respect to vocal level (dB). Future research will investigate other metrics of voice production with the goal of understanding the mechanisms underlying vocal effort and the external environmental influences on the perception of vocal effort.

Comparison of vocal fatigue and vocal tract discomfort between teachers of normal pupils and teachers of mentally disabled pupils

PURPOSE

This study aims to study the comparison of vocal fatigue and vocal tract discomfort between teachers of normal pupils and teachers of mentally disabled pupils.

STUDY DESIGN

Cross-sectional study METHODS: Participants were 179 teachers (50 male, 129 female) and 30 non-teachers (14 male, 16 female) who participated in the current study. The teachers work in elementary schools. Furthermore, 87 of the teachers work for mentally disabled pupils at special elementary schools. Non-teachers were Ahvaz Jundishapur University of Medical Sciences employees who consider as the control group. They completed the Persian VFI and VTDp questionnaires three times, at the beginning, middle, and end of their office hours for 1 workday.

RESULTS

The current study's findings indicate that the Persian VFI and VTD scores of non-teachers were significantly lower than teachers' scores. Furthermore, teachers of mentally disabled pupils demonstrated higher values from teachers of normal pupils based on the Persian VFI and VTDp scores CONCLUSION: The study results showed that teachers experienced more vocal fatigue and vocal tract discomfort than non-teachers. Furthermore, teachers of mentally disabled pupils indicated more vocal fatigue, the larynx's physical discomfort, and vocal tract discomfort, but this difference was practically small.

Voice and Respiratory Characteristics of Men and Women Seeking Treatment for Presbyphonia

BACKGROUND AND OBJECTIVES

Impaired respiratory function could potentially explain why some older speakers experience voice-related handicap whereas others do not, despite presenting with similar age-related laryngeal characteristics. The objectives of this study were therefore to (1) describe voice and respiratory function across men and women in a sample of treatment-seeking patients with presbyphonia; (2) assess how respiratory function differed from the general elderly population, based on normative data; and 3) discuss how respiratory function may play a role in the development of voice symptoms across men and women.

METHODS

Twenty one participants with presbyphonia underwent respiratory assessments (spirometry and respiratory muscle strength testing) in addition to standard of care voice assessments. Respiratory variables included forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), FEV₁/FVC, maximum inspiratory pressure (MIP), and maximum expiratory pressure (MEP).

RESULTS

Voice features were consistent with the diagnosis of presbyphonia and values did not different significantly between males and females, although some trends were noted. Regarding respiratory variables, one-third of the participants (n = 7) presented with FVC and FEV₁ less than 80% of predicted, and 57% (n = 12) were <90% of predicted. Nine percent of the males (n = 1) and none of the females had a MIP below the lower limit of normal (LLN) expected for their age, sex, and weight. Eighteen percent of the males (n = 2) and 20% of the females (n = 2) fell below the LLN for MEP.

CONCLUSION

Our sample of participants with presbyphonia included a non-negligible proportion of patients with decreased percent predicted values of FVC and FEV₁, and with respiratory muscle strength (MEP) below the LLN. Standardized values of pulmonary function were not different across sexes, indicative of a similar respiratory health. However, a lower raw pulmonary function and respiratory muscle strength in women may compound laryngeal changes and have an impact on perceived voice-related handicap. Together, findings warrant further studies to explore the impact of decreased respiratory function on voice and, ultimately, on the response to voice therapy in patients with presbyphonia.

Reproducibility of Voice Parameters: The Effect of Room Acoustics and Microphones

INTRODUCTION

Computer analysis of voice recordings is an integral part of the evaluation and management of voice disorders. In many practices, voice samples are taken in rooms that are not sound attenuated and/or sound-proofed; further, the technology used is rarely consistent. This will likely affect the recordings, and therefore, their analyses.

OBJECTIVES

The objective of this study is to compare various acoustic outcome measures taken from samples recorded in a sound-proofed booth to those recorded in more common clinic environments. Further, the effects from six different commonly used microphones will be compared.

METHODS

Thirty-six speakers were recorded while reading a text and producing sustained vowels in a controlled acoustic environment. The collected samples were reproduced by a Head and Torso Simulator and recorded in three clinical rooms and in a sound booth using six different microphones. Newer measures (eg, Pitch Strength, cepstral peak prominence, Acoustic Voice Quality Index), as well as more traditional measures (eg Jitter, Shimmer, harmonics-to-noise ratio and Spectrum Tilt), were calculated from the samples collected with each microphone and within each room.

RESULTS

The measures which are more robust to room acoustic differences, background noise, and microphone quality include Jitter and smooth cepstral peak prominence, followed by Shimmer, Acoustic Voice Quality Index, harmonics-to-noise ratio, Pitch Strength, and Spectrum Tilt.

CONCLUSIONS

The effect of room acoustics and background noise on voice parameters appears to be stronger than the type of microphone used for the recording. Consequently, an appropriate acoustical clinical space may be more important than the quality of the microphone.

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.

Speech level parameters in very low and excessive reverberation measured with a contact-sensor-based device and a headworn microphone

This work deals with the effect of very low and excessive reverberation on speech sound pressure levels. Measurements were carried out in a semi-anechoic and reverberant room using a contact-sensor-based device fixed at the base of the neck and a headworn microphone placed at 2.5 cm from the speaker's mouth. Speakers produced short monologues and also described a map with the intent of correctly explaining directions to a listener 6 m away. A significant increase of about 2 dB in mean, equivalent, and mode speech levels in semi-anechoic compared to reverberant room was on average observed for the map description from recordings with the contact device, thus, highlighting an increased vocal intensity in dead rooms when the speech task had a communicative intent. Such reliable results were not found with the headworn microphone because speech levels were affected by noise recorded in the pauses. Particularly, the 30 ms logging interval brought to more severe errors in mode and mean speech levels compared to 1 s. When the pauses were removed and a logging interval of 30 ms was adopted, results were more consistent with those obtained with the contact sensor, but level differences between the two rooms still remained not significant.

Effects of added absorption on the vocal exertions of talkers in a reverberant room

Occupational speech users such as schoolteachers develop voice disorders at higher rates than the general population. Previous research has suggested that room acoustics may influence these trends. The research reported in this paper utilized varying acoustical conditions in a reverberant room to assess the effects on vocal parameters of healthy talkers. Thirty-two participants were recorded while completing a battery of speech tasks under eight room conditions. Vocal parameters were derived from the recordings and the statistically significant effects of room acoustics were verified using mixed-model analysis of variance tests. Changes in reverberation time (T₂₀), early decay time (EDT), clarity index (C₅₀), speech transmission index (STI), and room gain (G_RG) all showed highly correlated effects on certain vocal parameters, including speaking level standard deviation, speaking rate, and the acoustic vocal quality index. As T₂₀, EDT, and G_RG increased, and as C₅₀ and STI decreased, vocal parameters showed tendencies toward dysphonic phonation. Empirically derived equations are proposed that describe the relationships between select room-acoustic parameters and vocal parameters. This study provides an increased understanding of the impact of room acoustics on voice production, which could assist acousticians in improving room designs to help mitigate unhealthy vocal exertion and, by extension, voice problems.

The Effect of Pulmonary Function on the Incidence of Vocal Fatigue Among Teachers

INTRODUCTION

Females face a significantly higher risk of presenting with voice problems than males. This discrepancy has been associated with a number of differences in respiratory behavior and the physiology of the laryngeal and endocrine systems.

METHODS

In conjunction with established spirometry measures, the Vocal Fatigue Index (VFI) was used to determine (1) if there is a relationship between base pulmonary function and vocal fatigue among teachers; and (2) if that relationship is different in females from males. One hundred and twenty-two elementary and middle school teachers (96 females and 26 males) from the Jordan School District in Northern Utah participated in the study.

RESULTS

VFI factors were predictors of the outcomes of several raw spirometry measures for female participants, but the same predictive relationship was not found for male participants. Additionally, there appeared to be no relationship between VFI and spirometry measures in females when using normalized, rather than raw, spirometry metrics.

CONCLUSIONS

The results suggest that the pulmonary physiology that would result in reduced raw pulmonary function, in combination with other differences associated with gender, may lead to a greater incidence of vocal fatigue among female teachers than their male counterparts.

Work-related communicative profile of radio broadcasters: a case study

Purpose: To explore the short-term effect of work-related voice use on voice function, and noise exposure on hearing function among radio broadcasters. Method: A 1-week follow-up study with the participation of two radio broadcasters was conducted. Participants were monitored at the beginning and at the end of the working week. Premonitoring assessment on Monday (baseline measure) and postmonitoring assessment on Friday (follow-up measure) were performed to identify short-term effects of work-related conditions on voice and hearing function among radio broadcasters. Result: Changes in fundamental frequency postmonitoring at the end of the work week may be an indication of work-related vocal fatigue. Changes in the distribution and standard deviation of SPL during the monitoring from Monday to Friday may indicate control of the vocal loudness as a strategy to reduce vocal effort during broadcasting. During a 1-week follow-up, noise conditions during radio broadcasting were below occupational exposure limits and without noticeable consequences on hearing function. Conclusion: The work-related communicative profile of radio broadcasting, from this pilot study, suggests that although vocal demands in terms of vocal load may differ among broadcasters, the work-related conditions of broadcasting may play a role on vocal function among these occupational voice users. Concerning hearing function, our results indicate that occupational noise exposure represented minimal risk for hearing problems but the consequences of long-term noise exposure on hearing mechanisms may yet occur. Future studies with bigger sample sizes are warranted to confirm our results.

The relationship between acoustical and perceptual measures of vocal effort

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

Vocal Fry and Vowel Height in Simulated Room Acoustics

PURPOSE

The purpose of this study was to investigate the influence of room acoustics in the relationship between vowel height and vocal fry.

METHODS

This was a cross-sectional study. Participants (college students, n = 40) read the first six sentences of "The Rainbow Passage" under nine simulated room acoustic conditions. Using two words with low vowels (act, pot) and two words with high vowels (shape, strikes) preceding a voiceless stop, the presence/absence of vocal fry was assessed using an automatic detection script. Generalized estimation equations were used to investigate the relationship between percentage of vocal fry, vowel height, and room acoustics.

RESULTS

The percentage of vocal fry was significantly higher for the low-height vowels compared with the high-height vowels (β = 1.21; standard er ror = 0.35), and for pink background noise present (β = 0.89; standard error = 0.35) compared with the condition without artificial noise added.

CONCLUSION

The results of this study indicate that young college students are more likely to produce fry phonation when producing low-height vowels under pink background noise condition compared with no noise conditions and high-height vowels. This result is of special interest for voice clinicians when designing therapy plans and vocal assessment protocols with fry-like components.

Gender Differences in the Reporting of Vocal Fatigue in Teachers as Quantified by the Vocal Fatigue Index

OBJECTIVES

Occupational voice users report higher instances of vocal health problems. Women, who are more likely than men to report voice problems, are the largest members of some occupational voice users, such as teachers. While a common complaint among this population is vocal fatigue, it has been difficult to quantify. Therefore, the goal of this study is to quantify vocal fatigue generally in school teachers and investigate any related gender differences.

METHODS

Six hundred forty (518 female, 122 male) teachers were surveyed using an online questionnaire consisting in part of the Vocal Fatigue Index (VFI), an index specifically designed to quantify vocal fatigue.

RESULTS

Compared to vocally healthy adults, the teachers surveyed were 3 times as likely to report vocal tiredness or vocal avoidance and over 3 times as likely to report physical voice discomfort. Additionally, female teachers were more likely to have scores approaching those with dysphonia.

CONCLUSIONS

The VFI quantified elevated levels of vocal fatigue in teachers, with a significant prevalence of symptoms reported among females compared to males. Further, because the VFI indicated elevated complaints (between normal and dysphonic) in a population likely to be elevated, the VFI might be used to identify early indications of voice problems and/or track recovery.

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.