- Email: [email protected]
Effects of Vocal Demands on Voice Performance of Student Singers
Effects of Vocal Demands on Voice Performance of Student Singers *Maria Claudia Franca and †Jeanine F. Wagner, *yCarbondale, Illinois Summary: Purpose. The objective of this study was to investigate the effect of cumulative vocal demands on the voices of music students majoring in voice throughout an academic semester. Method. Acoustic and aerodynamic voice parameters captured across an academic semester were analyzed. This study was designed as a time-course investigation, in which all participants were tested individually at three separate times distributed equally over an academic semester. General effects were verified with the application of one-way within-participants analysis of variances with repeated measures. The equipment used for monitoring vocal behavior consisted of the Computerized Speech Lab, the Phonatory Aerodynamic System, and the Ambulatory Phonation Monitor, computerbased systems for the assessment of voice. Self-reported data regarding voice usage were also collected. Results. In this study, comparisons of voice parameters of student singers repeatedly measured throughout an extended period of time did not lead to statistically significant differences. Self-reported information suggested a reasonable level of knowledge and awareness regarding voice concerns in this population. Conclusions. The results of this study indicated consistent stability of voice acoustic and aerodynamic parameters in this group throughout an academic semester. Key Words: Singing voice–Voice acoustics and aerodynamics–Voice monitoring. INTRODUCTION Singing is among the functions that most critically rely on the voice. Continuous vocal production is an activity that involves a synchronized interaction of multiple physical processes such as respiration, phonation, and resonance.1 Refined singing is then a multivariate task that requires extensive education and training of these functions.2,3 Singers are expected to attain and maintain an optimal level of vocal performance to execute complex phonatory maneuvers.4 Vocal performing competence includes having a functional, healthy, and aesthetically acceptable voice; consequently, the training demands are high.5 In addition, the performing voice is frequently affected by extra loading environmental factors.6,7 Hence, singers are considered at risk of developing voice disorders,6,7 which can be quite debilitating for them, physically and psychologically.8–10 For this reason, elite voice performers are expected to acquire knowledge about caring for the vocal mechanism when learning voice technique.11–13 Plans to obtain and maintain vocal health must include proper voice usage education, particularly for professional purposes.2 Cumulative effects of laryngeal overload Professional voice users, a larger spectrum in which singers are included, have a tendency to expose their voices to elevated risk factors, not always preserving their vocal systems from the impact of excessive vocal usage.14,15 Major voice risk factors include using the voice without rest, voice usage in Accepted for publication July 9, 2014. Paper presented at the 43rd Annual Voice Foundation Symposium, 2014. From the *Communication Disorders and Sciences Program, Rehabilitation Institute, Southern Illinois University Carbondale, Carbondale, IL; and the ySchool of Music, Southern Illinois University Carbondale, Carbondale, IL. Address correspondence and reprint requests to Maria Claudia Franca, Communication Disorders and Sciences Program, Rehabilitation Institute, Southern Illinois University Carbondale, Carbondale, IL. E-mail: [email protected] Journal of Voice, Vol. -, No. -, pp. 1-9 0892-1997/$36.00 Ó 2014 The Voice Foundation http://dx.doi.org/10.1016/j.jvoice.2014.07.004
nonfavorable organic or environmental conditions, using the voice in an effortful manner, and reserving a limited time to recover after illness that affects the voice.1,7 As a consequence, singers may be prone to develop vocal cumulative effects symptoms associated with vocal fatigue, a condition associated with excessive voice demands placed on speakers, in which loss of phonatory abilities develops as phonatory effort increases.10 Voice fatigue is typically described by an array of self-reported symptoms related to the overtaxing of the larynx, leading to a chronic subjective sensation of voicing tiredness that tends to increase with voicing activity, and in many cases progresses with time.5,11,16–18 These symptoms are perceived as irregularities and changes in quality of voice, including restricted frequency and intensity ranges.19–22 The literature reveals that vocal fatigue symptoms may have a detrimental impact on vocational and economic goals of professional and preprofessional voice users, and consequently in their quality of life and psychological well being.20–23 It has been suggested that there is a gap between acquiring voice care knowledge and implementing vocal hygiene methods among professional users.24–28 An investigation conducted with students majoring in voice, acting, and broadcasting revealed that some future elite professional voice users fail to take precautions to care of their voice systems.12 This is compatible with results from an investigation, which demonstrated that radio students and professionals had a tendency to underestimate the consequences of overlooking vocal hygiene regimens among this population.1 A study using a similar design to the present investigation, conducted with a population of student teachers, indicated deterioration of acoustic and aerodynamic voice parameters investigated through an academic semester.29 Given these past findings suggesting that ongoing vocal demands can deteriorate vocal quality and stability in a population of student teachers, the same might be expected of singing students whose demands and load are comparable or potentially even more intense.
2 Research questions and hypothesis The research questions focused primarily on behavior of students majoring in voice through repeated observations of vocal acoustics and aerodynamics in student singers (a) using the Computerized Speech Lab (CSL; KayPENTAX, Montvale, NJ) and the Phonatory Aerodynamic System (PAS; KayPENTAX) in the voice laboratory, and (b) using the Ambulatory Phonation Monitor (APM; KayPENTAX) throughout a sustained period of time (ie, 7 hours) as a tentative identification of changes in vocal acoustics and behavior of student singers in natural settings. Complementary findings were related to vocal habits as well as subjective feelings and attitudes regarding voice usage surveyed with the voice profile of singers (VPS) created for this study (Appendix), and the Voice Handicap Index (VHI; Jacobson et al, 1997), a standardized method to examine psychosocial aspects of voice usage. It was initially hypothesized that cumulative vocal demands may have an adverse effect on the voice of student singers, as verified in association with other occupational voice categories.1,12,29 Because of the high occupational demands, it may be difficult for professional and preprofessional voice users to carry out proper voice care.28,30,31 Their voice production should be supported by appropriate education and training, including identification and elimination of voice overloading aspects.14,25,26,32,33 As high level and high demand performers, student singers may be at risk for developing voice disorders; their vocal behavior when singing and when speaking should be supported by a proper technique.34–36 This study was designed to investigate the effects of vocal demands that typically unfold during an academic semester on voice quality of students majoring in voice. The research questions were guided by the inspection of voice parameters of student singers over an academic semester to understand the specific needs of singers and student singers. Cumulative academic-related voice demands that typically unfold during an academic semester including regular curricular activities such as singing classes and rehearsals may have a detrimental impact on voice performance, leading to a risk of developing voice disorders. The effects of vocal demands on the voice have been described in the literature.10,16 A study conducted before this investigation using a population of student teachers revealed that cumulative vocal demands throughout an academic semester had a detrimental impact on voice performance of participants.29 Although the literature hints that increased vocal demands impact vocal fold functioning, there is limited empirical data on the relationship between cumulative vocal demands faced by student singers over the progress of an academic semester. Additional considerations concern a possible attenuating influence of previous voice training on potential effects of cumulative vocal demands on voice performance. METHOD Participants Eight university music students majoring in voice aged 22– 34 years and reporting a healthy voice history participated in
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this study. Two participants were respectively 30 and 34 years old at the time of data collection, whereas all others were aged between 22 and 27 years. Despite the slightly broad age range, participants reported a relatively narrow range of 4– 6 years of formal voice training. Four participants were female and four were male, all of them were native English speakers. To minimize differences in voice training experience, students were selected from a group with similar educational background: all had an undergraduate degree in music and were attending college classes at the same level, pursuing a Master’s degree in music with voice as their primary instrument.14,17 After appropriate approval by the institutional review board, students were invited to participate in the study. Materials Objective instrumentation. Objective voice assessment was conducted using the CSL, the PAS, and the APM, sophisticated computer-based systems used for acoustic and aerodynamic assessment of voice.37–39 The CSL and the PAS were located in the SIUC Voice Lab. The APM is a portable device, associated with the remaining voice laboratory components. Acoustic voice samples were collected in a quiet room using a microphone (Shure dynamic model BG with frequency response of 85–14 000 Hz). Voice samples were collected and analyzed with the application of the Multi-Dimension Voice Program (MDVP) module of the CSL model 4500 (KayPENTAX) used to capture and analyze voice parameters.37,40 Voice aerodynamic assessment was conducted using the PAS model 6600 (KayPENTAX). The PAS hardware external module consists of an ergonomic device with bilateral handles with integrated microphone, face mask, pneumotach, and pressure transducer.39 The APM (KayPENTAX) provided objective data associated with voice use generating the acoustic measures of F0 and sound pressure level (SPL) obtained through an accelerometer adhered to the base of the participant’s neck and connected by a cable to a hardware module worn in a waist pack. The data collected throughout periods of time were subsequently downloaded to a computer equipped with APM software for analysis.38 Variables The independent variable for each of the research questions in this study was the singing vocal demands (SVD) condition, defined as cumulative voice demands that develop throughout a typical academic semester (ie, 16 weeks), including group and individual singing lessons, rehearsals, and presentations. The dependent variables included objective acoustic and aerodynamic voice parameters, defined as noninvasive methods applied in observation and documentation of vocal function.41 The participants were individually assessed in the first, eighth, and 15th weeks of the academic semester, respectively. Acoustic measures provide quantitative assessment of voice quality and vocal function associated with sound waves,42–45 whereas aerodynamic measures refer to the motion of air passing through the region of the vocal folds during phonation.39
Maria Claudia Franca and Jeanine F. Wagner
Vocal Demands on Student Singers
Acoustic and aerodynamic voice parameters generate quantifications of the voice signal that are widely used in voice analysis and documentation and have been shown to be valuable in discriminating healthy and pathologic voices.46–51 In this study, acoustic and aerodynamic variations that could be connected with effects from cumulative vocal demands52–54 in student singers were examined, in association with the voice acoustic measures of F0, relative average perturbation (RAP), shimmer, noise-toharmonic ratio (NHR), voice turbulence index (VTI), and SPL, and the aerodynamic measure of voice airflow. Questionnaires. Self-reported information is often applied in studies that involve behavior change because it generates prompt and reliable results in investigations involving behavior estimation and modification.28,55 In this study, self-reported data were collected primarily to describe participants and alternatively as an attempt to understand possible associations among voice usage and voice performance. The VHI56 was developed to estimate feelings and limitations attributed to voice usage to enlighten voice production from the speaker’s perspective by gauging impressions regarding the effects of three broad aspects associated with voice use: functional, physical, and emotional.56 Although trained singers may not present a voice handicap, the VHI was used as an attempt to examine psychosocial aspects of voice usage with the application of a widely used standardized method. The VPS, designed for this study, included demographic data, in addition to questions related to vocal behavior, incidence of vocal fatigue symptoms, and general knowledge of voice care (Appendix). Procedures The participants were tested individually three separate times, equally distributed at the beginning, middle, and end of the academic semester (ie, first, eighth, and 15th weeks). All data were recorded in digital files and text files listing summary measures.38 The testing was applied to one participant per test day, beginning at 8 AM. On arriving, participants received instructions regarding the study and signed an informed consent form for participation. Next, they were asked to report voice-related habits and feelings by responding to the two questionnaires, VPS and VHI. Participants then (a) had their voice tested using the SIUC Voice Lab equipment (ie, CSL and PAS) and (b) wore the APM from 8:30 AM to 3:30 PM during a typical school day including singing lessons and related activities, representing a consistent timeframe associated with routine and activities attended by all participants involved in the study. Efforts to ensure measurement reliability included systematic methods applied in all trials, following procedures described in the literature by authorities44,57,58 as well as manufacturer’s guidelines.37–39 The microphone used to capture acoustic parameters in the voice laboratory was placed on a stand for stability at a distance of 10 cm from the lips at an angle of 45 to reduce aerodynamic noise from the mouth during speech.44 Additionally, each participant was instructed to stabilize the PAS external ergonomic device by
3
holding the bilateral handles while placing the mask firmly against their face, covering the entire mouth and nose.39 Five averaged repetitions of each voice laboratory assessment were recorded in an attempt to obtain reliable measures.57–59 Data collection for acoustic (ie, RAP, shimmer, NHR, and VTI) and aerodynamic (ie, airflow) measures involved the sustained vowel /a/. To control the variability of fundamental frequency and intensity across speech sound tokens, each participant was instructed to produce the vowel /a/ naturally (ie, without using vibrato) at a habitual pitch and loudness level for 5 seconds.60 The speech sound period extending from 1.0 to 3.0 second from onset of each utterance was then extracted for analysis. Calibration of instruments before data collection was conducted according to manufacturer’s instructions.37–39 Utterances for acoustic analysis were captured using the MDVP module of the CSL, a multiparameter acoustic analysis tool which acquires, analyzes, and displays voice parameters from vocalizations, such as RAP, shimmer, NHR, and VTI. Aerodynamic analysis focused on mean expiratory airflow, using the Comfortable Sustained Phonation protocol, the PAS. Objective data were also obtained from continuous voicing produced during a regular day, throughout a period of 7 hours, with the use of the APM. Experimental design General effects of SVD were examined with the application of one-way within-participants analysis of variances (ANOVAs) with repeated measures to data collected in three separated times equally distributed in the course of an academic semester to investigate the impact of cumulative demands on voice. Each participant served as self-control, keeping individual differences constant throughout the experiment.59 Additional comparisons using univariate ANOVAs involving F0 and intensity measures from the CSL and APM were conducted as an introductory attempt to understand vocal behavior in diverse settings and tasks. These exploratory analyses were performed with basis on similarities among acoustic principles used in the design of both instruments,37–39,60,61 despite the diversity of environments and equipment. Furthermore, because a change in the level of significance will affect the risk for both Type I and Type II error, the traditional alpha level of .05 was selected for all behaviors in this study.62–64 RESULTS This investigation involved four female and four male college students majoring in voice who provided voice acoustic and aerodynamic data. Averaged statistical profiles generated by laboratorial voice instruments were applied in statistical comparisons using SPSS software version 20.0 (IBM Corp, Armonk, NY). Results related to the effect of cumulative voice demands on voice parameters of student singers were analyzed with the application of ANOVAs. Descriptive statistics and normative data from all voice parameters measured in this study are included on Table 1. Statistical comparisons demonstrating comparisons across successive time samples are described as follows.
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TABLE 1. Descriptive Statistics Overall
N
M1
SD 1
M2
SD 2
M3
SD 3
M Total
SD Total
RAP Shimmer NHR VTI SPL (CSL) Airflow SPL (APM)
8 8 8 8 8 8 8
0.605 3.103 0.131 0.046 55.691 0.600 69.636
0.656 0.945 0.012 0.010 4.324 0.349 6.462
0.553 2.910 0.116 0.046 54.397 0.546 106.683
0.540 1.070 0.025 0.009 2.744 0.303 84.536
0.370 3.262 0.124 0.057 54.790 9.782 76.822
0.208 1.021 0.024 0.023 4.768 26.352 5.871
0.509 3.092 0.124 0.050 54.959 0.549 84.339
0.493 0.980 0.021 0.016 3.899 0.287 9.699
Males
N
NT*
M1
SD 1
M2
SD 2
M3
SD 3
M Total
SD Total
F0 (CSL) RAP Shimmer NHR VTI SPL (CSL) Airflow F0 (APM) SPL (APM)
4 4 4 4 4 4 4 4 4
132* 0.78* 3.81y 0.19y 0.006y 77.80z 0.133x 131* 77.80z
148.185 0.505 3.172 0.140 0.041 55.830 0.687 162.585 67.602
36.873 0.430 0.584 0.007 0.012 61.183 0.381 39.944 4.372
146.865 0.245 2.542 0.135 0.051 53.355 0.600 186.062 79.142
24.700 0.156 0.682 0.009 0.011 2.765 0.381 25.693 5.295
138.068 0.315 2.900 0.134 0.065 54.295 0.497 174.725 75.280
33.125 0.205 0.515 0.029 0.024 6.341 0.286 26.565 4.152
144.373 0.355 2.872 0.136 0.052 54.493 0.595 174.457 74.008
29.299 0.286 0.604 0.016 0.018 4.961 0.329 30.131 6.531
Females
N
NT*
M1
SD 1
M2
SD 2
M3
SD 3
M Total
SD Total
F0 (CSL) RAP Shimmer NHR VTI SPL (CSL) Airflow F0 (APM) SPL (APM)
4 4 4 4 4 4 4 4 4
224* 0.63* 3.81y 0.19y 0.006y 74.00z 0.133x 217* 74.00z
249.105 0.704 3.034 0.122 0.051 55.552 0.512 288.645 71.670
39.231 0.890 1.313 0.010 0.007 2.311 0.345 28.955 8.202
261.725 0.861 3.277 0.097 0.041 55.440 0.492 296.232 134.225
56.665 0.635 1.359 0.020 0.005 2.651 0.248 77.090 120.930
264.586 0.426 3.624 0.114 0.050 55.285 0.505 276.367 78.117
57.330 0.226 1.349 0.016 0.022 3.491 0.195 50.058 7.567
258.472 0.664 3.312 0.111 0.047 55.425 0.503 287.078 94.670
47.341 0.612 1.239 0.018 0.013 2.590 0.244 51.048 69.880
Abbreviations: M, mean; NT*, normative threshold; SD, standard deviation. * Colton et al (2011).53 y KayPENTAX (2008).39 z Hillman & Kobler (1999).68 x Zraick et al (2011).69
Voice laboratory acoustic parameters Comparisons involving voice laboratory acoustic parameters described in the research questions were not found to have statistical significance. Acoustic results were RAP F(2, 14) ¼ 1.022, P ¼ 0.385; shimmer F(2, 14) ¼ 0.449, P ¼ 0.647; NHR F(2, 14) ¼ 1.950, P ¼ 0.179, VTI F(2, 14) ¼ 1.709, P ¼ 0.217; SPL F(2, 14) ¼ 0.193, P ¼ 0.826 (Table 2). Aerodynamic parameters Additionally, comparisons involving airflow measurements did not reveal statistically significant results: F(2, 14) ¼ 0.988, P ¼ 0.397 (Table 3). Further analyses using participants grouped by gender also did not to lead to statistically significant changes. APM parameters Comparisons related to F0 and SPL collected during 7 hours did not reach statistically significant results. F0 and SPL results were F0 F(2, 14) ¼ 1.265, P ¼ 0.313; SPL F(2, 14) ¼ 1.442, P ¼ 0.269 (Table 4).
Comparisons of measures collected using voice laboratory and ambulatory monitoring materials Comparisons involving parameters collected using diverse materials and tasks were conducted as an exploratory attempt to further analyze vocal behaviors in student singers. F0 and SPL measures obtained from laboratorial and ambulatorial materials were compared using ANOVAs. Results revealed statistically significant differences in F0 (F0 F(1, 23) ¼ 13.077, P ¼ 0.000) but not in SPL (SPL F(1, 23) ¼ 0.767, P ¼ 0.622; Table 5). Overall, participants tended to use higher F0 and SPL in natural conditions.
Sex-specific results Subsequent examination of data revealed statistical significance associated with NHR measured in females: F(2, 6) ¼ 9.253, P ¼ 0.015. Additionally, SPL measured using ambulatory monitoring demonstrated significant differences in males F(2, 6) ¼ 5.307, P ¼ 0.047 (Table 6).
Maria Claudia Franca and Jeanine F. Wagner
TABLE 2. Singing Vocal Demands (SVD) on Voice Laboratory Acoustic Parameters: Repeated Measures Parameter
Sum of Squares
F0 Within 127.810 participants Error 16 566.663 RAP Within 0.243 participants Error 1.661 Shimmer Within 0.499 participants Error 7.766 NHR 0.001 Within participants Error 0.004 VTI Within 0.001 participants Error 0.003 SPL Within 7.040 participants Error 254.857
df 2
Mean Square
F
TABLE 4. Singing Vocal Demands (SVD) on APM Parameters: Repeated Measures Sig.
63.905 0.054 0.948
14 1183.333 2 14 2 14 2 14 2 14 2 14
0.121 1.022 0.385 0.119 0.249 0.449 0.647
0.000 1.950 0.179 0.000 0.000 1.709 0.217 0.000 3.520 0.193 0.826 18.204
Questionnaires Participants completed the VPS and the VHI questionnaires when having the first voice measurement. Approximately 50% of the participants reported that they sometimes use their voice with excessive effort; 25% of the participants reported having occasional to frequent symptoms of hoarseness and sore throat. In general, the participants indicated knowledge of voice care as suggested by reports of following systematic vocal warm-up techniques (100%), maintaining adequate body hydration (90%), avoiding environmental and functional vocal stresses involving background noise and laryngeal irritant substances (90%), and resting the vocal mechanism as needed (90%). In addition, 50% of the participants responded that
TABLE 3. Singing Vocal Demands (SVD) on a Voice Laboratory Aerodynamic Parameter: Repeated Measures
Airflow Within participants Error
Parameter
Sum of Squares
df
Mean Square
F
Sig.
SPL Within 6175.610 2 3087.805 1.442 0.269 participants Error 29 973.613 14 2140.972 F0 Within 1608.524 2 804.262 1.265 0.313 participants Error 8901.948 14 635.853 Notes: Computed using alpha ¼ 0.05. Sig., Statistical significance.
0.555
Notes: Computed using alpha ¼ .05. Sig., Statistical significance.
Parameter
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Vocal Demands on Student Singers
Sum of Squares
df
Mean Square
F
Sig.
452.345
2
226.173
0.988
0.397
3204.493
14
228.892
Notes: Computed using alpha ¼ .05. Sig., Statistical significance.
they would seek professional help when experiencing voicerelated problems. Moreover, none of them were smokers (Table 7). Results from the VHI survey revealed concerns mostly related to physical and functional aspects of voice. The highest VHI scores associated with physical aspects of voice referred to concerns about voice quality variations, whereas functional aspects of voice involved intelligibility and communication effectiveness. DISCUSSION In this study, voice parameters of student singers measured throughout an academic semester were analyzed. The participants were eight college music students majoring in voice, with a range of 4–6 years of formal voice training; four were males and four females. Although some statistically significant differences were found in association with results grouped by sex, negative overall comparisons of acoustic and aerodynamic measures were verified. Complementary self-reported information provided further insight into voice usage among student singers. Responses obtained from both VPS and VHI surveys signaled an overall understanding of the voice mechanism and the need of its preservation, as well as a focus on adequate
TABLE 5. Comparisons Between F0 and SPL in the Voice Laboratory and in Natural Settings Parameter
Sum of Squares
df
Mean Square
F
Sig.
SPL Between 87.915 1 12.559 0.767 0.622 groups Error 261.898 23 16.369 F0 Between 95 514.019 1 13 644.860 13.077 0.000 groups Error 166 994.473 23 1043.405 Notes: Computed using alpha ¼ .05. Sig., Statistical significance.
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TABLE 6. Singing Vocal Demands (SVD) on Voice Parameters: SexRelated Statistically Significant Results Parameter NHR females Within participants Error SPL APM males Within participants Error
Sum of Squares
df
Mean Square
0.001
2
0.001
F
Sig.
0.001
9.253
0.015
2
0.001
9.253
0.015
278.727
2
139.364
5.307
0 .047
157.575
6
26.263
Notes: Computed using alpha ¼ .05. Sig., Statistical significance.
usage of voice. It seems like, despite indications of eventual voice fatigue, awareness regarding voice care procedures supported voice stability in this group. These essentially negative results may imply that previous voice training may support vocal health, particularly in light of a previous similar study encompassing a population allegedly not trained in voice techniques.29 The aforementioned investigation, conducted with a population of student teachers using materials, procedures, and variables identical to this study, led to results that suggest that in a group of preprofessional voice users with no prior formal voice training, cumulative vocal demands that take place through a typical academic semester resulted in actual deterioration of most voice parameters investigated (ie, F0, RAP, shimmer, and NHR in the voice laboratory, and SPL in ambulatory conditions). In addition, responses from identical questionnaires (ie, VPS and VHI) applied to student teachers revealed a general reduced awareness regarding voice care among
student teachers, which may have a connection with changes indicating progressive instability in that population, in the course of an academic semester. These discrepancies between results from preprofessional groups being prepared to use the professional voice in two diverse areas (ie, singing and teaching) hint that formal voice training is supportive to voice stability and quality. It is important to consider that singers may belong to a group whose vocal physiology is somehow resistant because of innate characteristics and training.32 Nevertheless, these results corroborate views that indicate that singers, as elite professional voice users, have an appreciation for a general state of health that contribute to their work performance, as evidenced by the self-report data.65 Overall, both male and female participants used higher F0 and SPL in circumstances related to academic environments, which may be simply due to specific needs essentially pertinent to singing performance. It is critical to note that comparisons among samples collected in diverse conditions were conducted in an effort to clarify contrasting behaviors associated with voice production in diverse situations. Despite the limitations involved in attempting to compare measures obtained from different tasks, settings, and equipment and thus subjected to influences of factors such as diverse microphone signal and acoustic environment issues,44,63,66 these results may help in providing future research directions for proper comparisons. Although it was not the focus of this study to analyze all single possibilities, it is interesting to observe that not every outcome was consistent with the majority of data. Although supported by systematic procedures, the method did not create similar results in every participant. For example, the male who exhibited the largest overall perturbation values (ie, participant 1) reported having frequent voice symptoms such as hoarseness, sore throat, and persistent throat cleaning, despite
TABLE 7. Summary of the VPS Responses Component Gender Age Educational degree Voice training Typical environment, loudness, and pitch of voice usage Estimated hours per day speaking Smokers Drink at least four glasses of water a day Self-reported voice problems
Self-reported voice care
Description Four females, four males Range: 22–34 y; mean: 26 y Eight participants holding a bachelor’s degree Range: 4–6 y Home and school Range: 2–12 0 8 Hoarseness: two participants Voice loss: two participants Sore throat: two participants Voicing effort: three participants Regular vocal warming: eight participants Regular adequate body hydration: seven participants Avoid competition with background noise: seven participants Avoid smoky environments: seven participants Take voice breaks: seven participants Would see a doctors as needed: four participants
Maria Claudia Franca and Jeanine F. Wagner
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Vocal Demands on Student Singers
TABLE 8. Individual Values Part
Gender
Month
F0 CSL
RAP
Shimmer
NHR
VTI
SPL CSL
Airflow
F0 APM
SPL APM
1 1 1 2 2 2 3 3 3 4 4 4 5 5 5 6 6 6 7 7 7 8 8 8
Male Male Male Female Female Female Female Female Female Male Male Male Female Female Female Male Male Male Female Female Female Male Male Male
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
139.080 143.814 109.555 222.946 325.064 336.277 288.949 293.412 283.359 185.578 175.695 110.383 275.818 221.354 231.119 100.892 115.844 174.331 208.707 207.070 207.591 167.190 152.109 158.005
1.111 0.464 0.232 0.545 0.319 0.428 0.126 0.818 0.339 0.518 0.142 0.153 0.139 0.546 0.202 0.203 0.252 0.616 2.008 1.764 0.735 0.191 0.122 0.261
3.889 2.068 2.928 3.255 2.616 3.428 1.674 1.700 1.849 3.411 1.925 2.763 2.453 4.632 5.015 2.717 3.402 2.335 4.754 4.163 4.206 2.674 2.775 3.577
0.144 0.130 0.109 0.123 0.097 0.104 0.110 0.068 0.104 0.145 0.135 0.144 0.123 0.109 0.113 0.143 0.148 0.112 0.135 0.114 0.138 0.130 0.127 0.171
0.052 0.037 0.064 0.046 0.040 0.026 0.044 0.036 0.039 0.025 0.047 0.064 0.058 0.041 0.058 0.039 0.060 0.036 0.056 0.049 0.078 0.051 0.060 0.097
56.100 54.350 51.620 52.430 53.010 59.900 56.600 55.470 56.080 64.370 56.790 50.490 57.820 59.120 52.620 52.630 51.550 63.780 55.360 54.160 52.540 50.220 50.730 51.290
0.990 1.150 0.520 0.340 0.430 0.570 1.030 0.860 0.750 1.020 0.540 0.180 0.320 0.340 0.380 0.500 0.430 0.870 0.360 0.340 0.320 0.240 0.280 0.420
168.060 176.390 175.210 264.860 286.460 266.490 296.050 306.260 327.290 199.260 218.180 199.020 267.140 202.210 211.210 105.990 157.470 137.640 326.490 390.000 300.480 177.030 192.210 187.030
68.570 75.260 79.590 67.640 78.300 75.490 62.340 68.130 70.520 65.150 78.150 69.870 76.190 74.960 77.990 63.380 86.880 74.550 80.510 315.510 88.470 73.310 76.280 77.110
indications of awareness and application of habitual voice care including proper hydration, use of vocal warm-up exercises, and avoidance of voice irritating environmental components. Likewise, the female (ie, participant 7) who demonstrated the largest perturbation values reported similar voice disturbances, in spite of following common vocal hygiene techniques (Table 8). These incidences may be explained in part by the fact that participants 1 and 7 reported having seasonal and occasional allergy symptoms. Furthermore, it is interesting to note that only 50% of the subjects indicated that they would seek professional help should they experience vocal difficulties. Finally, in addition to previously raised concerns regarding possible inherent characteristics of participants and implications of results generated during ambulatory monitoring, findings need to be interpreted with caution because they derived from a limited sample. The present study used participants who belong to a specific environment of voice usage, as a manner of obtaining experimental control by avoiding confounding factors caused by extraneous variables.61,67 Furthermore, concerns regarding accuracy of self-reported information were addressed by emphasizing confidentially of results and stressing the importance of generating precise scientific data to implement future plans in voice care.65
CONCLUSIONS This study attempted to underline the importance of clarifying and quantifying the relationship of vocal demands and voice performance among student singers. Results apply to both
educational aspects of vocal health and the development of preventive measures for voice disorders in student singers as well as in professional and preprofessional voice users in general. Elite occupational voice users such as singers should be provided with quality information regarding voice care.18,26,65 To propose effective plans to prevent voice disorders in occupational voice users, including singers, it is important to understand aspects of their vocal behavior. This study attempted to identify vocal behavior of student singers by examining vocal acoustics and aerodynamics throughout an extended period with laboratory acoustic and aerodynamic-oriented equipment (ie, CSL, PAS). Additionally, following a growing trend of interest in applying devices for monitoring body systems while individuals perform natural daily activities, this study used a portable device that collects objective data throughout extended periods (ie, APM).19,38 Self-reported data surveyed as supplementary information regarding voice-related aspects from the participants’ standpoint56 seemed to substantiate indications of voice stability in this population, apparently in association with extensive formal training. Additional results of this investigation, conveying the relationship between direct APM measures and vocal acoustics and aerodynamics measured by the CSL and the PAS, indicated different vocal behaviors in the voice laboratory and during ambulatory monitoring that could be due to performancerelated needs. It is hoped that the results of this study help in clarifying the importance of education and awareness about vocal health. It is also hoped that this study will inspire extended investigations to
8 elucidate the impact of voice training for voice enhancement as well as a possible associated attenuation effects of vocal overload, particularly among professional voice users. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jvoice.2014.07.004. REFERENCES 1. Timmermans B, De bodt M, Wuyts F, Van de heyning P. Vocal hygiene in radio students and in radio professionals. Logoped Phoniatr Vocol. 2003; 28:127–132. 2. Benninger MS. The professional voice. J Laryngol Otol. 2011;125: 111–116. 3. Hutchins SM, Peretz I. A frog in your throat or in your ear? Searching for the causes of poor singing. J Exp Psychol Gen. 2012;141:76–97. 4. Zeitels SM, Hillman RE, Desloge R, Mauri M, Doyle PB. Phonomicrosurgery in singers and performing artists: treatment outcomes, management theories, and future directions. Ann Otol Rhinol Laryngol Suppl. 2002; 190:21–40. 5. Timmermans B, Vanderwegen J, De bodt MS. Outcome of vocal hygiene in singers. Curr Opin Otolaryngol Head Neck Surg. 2005;13:138–142. 6. Verdolini-Marston K, Titze IR, Druker DG. Changes in phonation threshold pressure with induced conditions of hydration. J Voice. 1990;4:142–151. 7. Vilkman E, Lauri ER, Alku P, Sala E, Sihvo M. Loading changes in timebased parameters of glottal flow waveforms in different ergonomic conditions. Folia Phoniatr Logop. 1997;49:247–263. 8. Cohen SM, Jacobson BH, Garrett CG, et al. Creation and validation of the Singing Voice Handicap Index. Ann Otol Rhinol Laryngol. 2007;116: 402–406. 9. Phyland DJ, Oates J, Greenwood KM. Self-reported voice problems among three groups of professional singers. J Voice. 1999;13:602–611. 10. McCabe DJ. Chant therapy for treating vocal fatigue among public school teachers: a preliminary study. Am J Speech Lang Pathol. 2002;11:356–369. 11. Braun-janzen C, Zeine L. Singers’ interest and knowledge levels of vocal function and dysfunction: survey findings. J Voice. 2009;23:470–483. 12. Timmermans B, De bodt MS, Wuyts FL, et al. Poor voice quality in future elite vocal performers and professional voice users. J Voice. 2002;16:372–382. 13. Webb J. Promoting vocal health in the choral rehearsal. Music Educ J. 2007;93:26–31. 14. Broaddus-Lawrence PL, Treole K, McCabe RB, Allen RL, Toppin L. The effects of preventive vocal hygiene education on the vocal hygiene habits and perceptual vocal characteristics of training singers. J Voice. 2000;14: 58–71. 15. Van der Merwe A, Van Tonder M, Pretorius E, Crous H. Voice problems in some groups of professional users of voice: implications for prevention. S Afr J Commun Disord. 1996;43:41–51. 16. Mattiske JA, Oates JM, Greenwood KM. Vocal problems among teachers: a review of prevalence, causes, prevention, and treatment. J Voice. 1998;12: 489–499. 17. Welham NV, Maclagan MA. Vocal fatigue in young trained singers across a solo performance: a preliminary study. Logoped Phoniatr Vocol. 2004;29: 3–12. 18. Verdolini K, Ramig LO. Review: occupational risks for voice problems. Logoped Phoniatr Vocol. 2001;26:37–46. 19. Hillman RE, Mehta DD. Ambulatory monitoring of daily voice use. Perspect Voice Voice Disord. 2011;21:56–61. 20. Kitch JA, Oates J. The perceptual features of vocal fatigue as self-reported by a group of actors and singers. J Voice. 1994;8:207–214. 21. Titze IR. Toward occupational safety criteria for vocalization. Logoped Phoniatr Vocol. 1999;24:49–54. 22. Verdolini K. Critical analysis of common terminology in voice therapy. Phonoscope. 1999;2:1–8. 23. Behlau M, Oliveira G. Vocal hygiene for the voice professional. Curr Opin Otolaryngol Head Neck Surg. 2009;17:149–154.
Journal of Voice, Vol. -, No. -, 2014 24. Ilomaki I, Laukkanen AM, Leppanen K, Vilkman E. Effects of voice training and voice hygiene education on acoustic and perceptual speech parameters and self-reported vocal well-being in female teachers. Logoped Phoniatr Vocol. 2008;33:83–92. 25. Sapir S. Vocal attrition in voice students: survey findings. J Voice. 1993;7: 69–74. 26. Sataloff R. Professional voice: the science and art of clinical care. San Diego, CA: Plural Publishing; 2005. 27. Vilkman E. Voice problems at work: a challenge for occupational safety and health arrangement. Folia Phoniatr Logop. 2000;52:120–125. 28. Hackworth RS. The effect of vocal hygiene and behavior modification instruction on the self-reported vocal health habits of public school music teachers. Int J Music Educ. 2007;25:20–28. 29. Franca MC. A comparison of vocal demands with vocal performance among classroom student teachers. J Commun Disord. 2013;46:111–123. 30. Dishman RK. Compliance/adherence in health-related exercise. Health Psychol. 1982;1:237–267. 31. Roy N, Weinrich B, Gray SD, et al. Voice amplification versus vocal hygiene instruction for teachers with voice disorders: a treatment outcomes study. J Speech Lang Hear Res. 2002;45:625–638. 32. Boone DR, McFarlane SC, Berg SL, Zraick RI. The voice and voice therapy. 8th ed. Boston, MA: Pearson Higher Ed; 2013. 33. David M. Designing a program of vocal hygiene for singers. J Singing. 1996;53:15–20. 34. Ramig LO, Verdolini K. Treatment efficacy: voice disorders. J Speech Lang Hear Res. 1998;41:S101–S116. 35. Andrews ML. Intervention with young voice users: a clinical perspective. J Voice. 1993;7:160–164. 36. Gregg WJ. On exercises physiology and voice. J Singing. 1996;54:47–49. 37. KayPentax. CSL instruction manual. Montvale, NJ: KayPentax; 2008. 38. KayPentax. APM instruction manual. Montvale, NJ: KayPentax; 2009. 39. KayPentax. PAS instruction manual. Montvale, NJ: KayPentax; 2010. 40. Gonzalez J, Carpi A. Early effects of smoking on the voice: a multidimensional study. Med Sci Monit. 2004;10:CR649–656. 41. Gelfer MP, Andrews ML, Schmidt CP. Effects of prolonged loud reading on selected measures of vocal function in trained and untrained singers. J Voice. 1991;5:158–167. 42. Baken RJ, Orlikoff RF. Clinical measurement of speech and voice. 2nd ed. San Diego, CA: Cengage Learning; 2000. 43. Titze IR. Principles of voice production. 2nd ed. Salt Lake City, UT: National Center for Voice and Speech; 2000. 44. Titze IR. Workshop on voice acoustic analysis summary statement. Workshop on voice acoustic analysis sponsored by the National Center for Voice and Speech, Denver, CO; 1994. 45. Kent RD, Ball JM. Voice quality measurement. San Diego, CA: Singular; 2000. 46. Askenfelt AG, Hammarberg B. Speech waveform perturbation analysis: a perceptual-acoustical comparison of seven measures. J Speech Hear Res. 1986;29:50–64. 47. Deliyski DD. Acoustic model and evaluation of pathological voice production. Paper presented at the Third Conference on Speech Communication and Technology Eurospeech. Berlin, Germany; 1993. 48. Di Nicola V, Fiorella ML, Spinelli DA, Fiorella R. Acoustic analysis of voice in patients treated by reconstructive subtotal laryngectomy. Evaluation and critical review. Acta Otorhinolaryngol Ital. 2006;26:59–68. 49. Hamdan A, Medawar W, Younes A, Bikhazi H, Fuleihan N. The effects of hemodialysis on voice: an acoustic analysis. J Voice. 2005;19:290–305. 50. Hodge FS, Colton RH, Kelley RT. Vocal intensity characteristics in normal and elderly speakers. J Voice. 2001;15:503–511. 51. Schoentgen J. Qualitative evaluation of the discriminating performance of acoustic features in detecting laryngeal pathology. Speech Commun. 1982; 1:269–282. 52. Brockmann M, Storck C, Carding PN, Drinnan MJ. Voice loudness and gender effects on jitter and shimmer in healthy adults. J Speech Hear Res. 2008;51:1152–1160. 53. Colton RH, Casper JK, Leonard R. Understanding voice problems: a physiological perspective for diagnosis and treatment. 4th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2011.
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54. Sapienza CM, Hoffman-Ruddy B. Voice disorders. San Diego, CA: Plural Publishing; 2009. 55. Baranowski T. Methodologic issues in self-report of health behavior. J Sch Health. 1985;55:179–182. 56. Jacobson B, Johnson A, Grywalski C, et al. The voice handicap index (VHI): development and validation. Am J Speech Lang Pathol. 1997;6:66–70. 57. Behlau M, Alves ML, Oliveira G. Cross-cultural adaptation and validation of the voice handicap index into Brazilian Portuguese. J Voice. 2011;25: 354–359. 58. Bonetti A, Bonetti L. Cross-cultural adaptation and validation of the Voice Handicap Index into Croatian. J Voice. 2013;27:130–140. 59. Scherer RC, Vail VJ, Guo CG. Required number of tokens to determine representative voice perturbation values. J Speech Hear Res. 1995;38:1260–1269. 60. Karnell MP, Scherer RS, Fischer LB. Comparison of acoustic voice perturbation measures among three independent voice laboratories. J Speech Hear Res. 1991;34:781–790. 61. Huck SW. Reading statistics and research. Boston, MA: Allyn & Bacon; 2000. 62. Skoog DA, Holler JF, Crouch SR. Principles of instrumental analysis. Pacific Grove, CA: Brooks Cole; 2006.
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63. Winholtz WS, Titze IR. Conversion of a head-mounted microphone signal into calibrated SPL units. J Voice. 1997;11:417–421. 64. Stevens J. Applied multivariate statistics for the social sciences. Hillsdale, NJ: Lawrence Erlbaum Associates; 1994. 65. Rubin J, Korovin G, Epstein R. Special considerations for the professional voice user. In: Rubin JS, Sataloff T, Korovin GS, eds. Diagnosis and treatment of voice disorders. 2nd ed. Albany, NY: Demar Learning; 2003: 583–595. 66. Asplund A. How loud was it? A calibration system for voice recording in clinical and research applications. In: Proceedings of the 26th World Congress of Logopedics and Phoniatrics. Brisbane, Australia: International Association of Logopedics and Phoniatrics; 2004. 67. Christensen LB. Experimental methodology. Boston, MA: Allyn & Bacon; 2004. 68. Hillman RE, Kobler JB. Aerodynamic measures of voice production. In: Ball M, Kent R, eds. The Handbook of Voice Quality Measurement. San Diego, CA: Singular Press; 1999:245–255. 69. Zraick RI, Smith-Olinde L, Shotts LL. Adult normative data for the KayPENTAX Phonatory Aerodynamic System Model 6600. J Voice. 2012; 26:164–176.
nonfavorable organic or environmental conditions, using the voice in an effortful manner, and reserving a limited time to recover after illness that affects the voice.1,7 As a consequence, singers may be prone to develop vocal cumulative effects symptoms associated with vocal fatigue, a condition associated with excessive voice demands placed on speakers, in which loss of phonatory abilities develops as phonatory effort increases.10 Voice fatigue is typically described by an array of self-reported symptoms related to the overtaxing of the larynx, leading to a chronic subjective sensation of voicing tiredness that tends to increase with voicing activity, and in many cases progresses with time.5,11,16–18 These symptoms are perceived as irregularities and changes in quality of voice, including restricted frequency and intensity ranges.19–22 The literature reveals that vocal fatigue symptoms may have a detrimental impact on vocational and economic goals of professional and preprofessional voice users, and consequently in their quality of life and psychological well being.20–23 It has been suggested that there is a gap between acquiring voice care knowledge and implementing vocal hygiene methods among professional users.24–28 An investigation conducted with students majoring in voice, acting, and broadcasting revealed that some future elite professional voice users fail to take precautions to care of their voice systems.12 This is compatible with results from an investigation, which demonstrated that radio students and professionals had a tendency to underestimate the consequences of overlooking vocal hygiene regimens among this population.1 A study using a similar design to the present investigation, conducted with a population of student teachers, indicated deterioration of acoustic and aerodynamic voice parameters investigated through an academic semester.29 Given these past findings suggesting that ongoing vocal demands can deteriorate vocal quality and stability in a population of student teachers, the same might be expected of singing students whose demands and load are comparable or potentially even more intense.
2 Research questions and hypothesis The research questions focused primarily on behavior of students majoring in voice through repeated observations of vocal acoustics and aerodynamics in student singers (a) using the Computerized Speech Lab (CSL; KayPENTAX, Montvale, NJ) and the Phonatory Aerodynamic System (PAS; KayPENTAX) in the voice laboratory, and (b) using the Ambulatory Phonation Monitor (APM; KayPENTAX) throughout a sustained period of time (ie, 7 hours) as a tentative identification of changes in vocal acoustics and behavior of student singers in natural settings. Complementary findings were related to vocal habits as well as subjective feelings and attitudes regarding voice usage surveyed with the voice profile of singers (VPS) created for this study (Appendix), and the Voice Handicap Index (VHI; Jacobson et al, 1997), a standardized method to examine psychosocial aspects of voice usage. It was initially hypothesized that cumulative vocal demands may have an adverse effect on the voice of student singers, as verified in association with other occupational voice categories.1,12,29 Because of the high occupational demands, it may be difficult for professional and preprofessional voice users to carry out proper voice care.28,30,31 Their voice production should be supported by appropriate education and training, including identification and elimination of voice overloading aspects.14,25,26,32,33 As high level and high demand performers, student singers may be at risk for developing voice disorders; their vocal behavior when singing and when speaking should be supported by a proper technique.34–36 This study was designed to investigate the effects of vocal demands that typically unfold during an academic semester on voice quality of students majoring in voice. The research questions were guided by the inspection of voice parameters of student singers over an academic semester to understand the specific needs of singers and student singers. Cumulative academic-related voice demands that typically unfold during an academic semester including regular curricular activities such as singing classes and rehearsals may have a detrimental impact on voice performance, leading to a risk of developing voice disorders. The effects of vocal demands on the voice have been described in the literature.10,16 A study conducted before this investigation using a population of student teachers revealed that cumulative vocal demands throughout an academic semester had a detrimental impact on voice performance of participants.29 Although the literature hints that increased vocal demands impact vocal fold functioning, there is limited empirical data on the relationship between cumulative vocal demands faced by student singers over the progress of an academic semester. Additional considerations concern a possible attenuating influence of previous voice training on potential effects of cumulative vocal demands on voice performance. METHOD Participants Eight university music students majoring in voice aged 22– 34 years and reporting a healthy voice history participated in
Journal of Voice, Vol. -, No. -, 2014
this study. Two participants were respectively 30 and 34 years old at the time of data collection, whereas all others were aged between 22 and 27 years. Despite the slightly broad age range, participants reported a relatively narrow range of 4– 6 years of formal voice training. Four participants were female and four were male, all of them were native English speakers. To minimize differences in voice training experience, students were selected from a group with similar educational background: all had an undergraduate degree in music and were attending college classes at the same level, pursuing a Master’s degree in music with voice as their primary instrument.14,17 After appropriate approval by the institutional review board, students were invited to participate in the study. Materials Objective instrumentation. Objective voice assessment was conducted using the CSL, the PAS, and the APM, sophisticated computer-based systems used for acoustic and aerodynamic assessment of voice.37–39 The CSL and the PAS were located in the SIUC Voice Lab. The APM is a portable device, associated with the remaining voice laboratory components. Acoustic voice samples were collected in a quiet room using a microphone (Shure dynamic model BG with frequency response of 85–14 000 Hz). Voice samples were collected and analyzed with the application of the Multi-Dimension Voice Program (MDVP) module of the CSL model 4500 (KayPENTAX) used to capture and analyze voice parameters.37,40 Voice aerodynamic assessment was conducted using the PAS model 6600 (KayPENTAX). The PAS hardware external module consists of an ergonomic device with bilateral handles with integrated microphone, face mask, pneumotach, and pressure transducer.39 The APM (KayPENTAX) provided objective data associated with voice use generating the acoustic measures of F0 and sound pressure level (SPL) obtained through an accelerometer adhered to the base of the participant’s neck and connected by a cable to a hardware module worn in a waist pack. The data collected throughout periods of time were subsequently downloaded to a computer equipped with APM software for analysis.38 Variables The independent variable for each of the research questions in this study was the singing vocal demands (SVD) condition, defined as cumulative voice demands that develop throughout a typical academic semester (ie, 16 weeks), including group and individual singing lessons, rehearsals, and presentations. The dependent variables included objective acoustic and aerodynamic voice parameters, defined as noninvasive methods applied in observation and documentation of vocal function.41 The participants were individually assessed in the first, eighth, and 15th weeks of the academic semester, respectively. Acoustic measures provide quantitative assessment of voice quality and vocal function associated with sound waves,42–45 whereas aerodynamic measures refer to the motion of air passing through the region of the vocal folds during phonation.39
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Vocal Demands on Student Singers
Acoustic and aerodynamic voice parameters generate quantifications of the voice signal that are widely used in voice analysis and documentation and have been shown to be valuable in discriminating healthy and pathologic voices.46–51 In this study, acoustic and aerodynamic variations that could be connected with effects from cumulative vocal demands52–54 in student singers were examined, in association with the voice acoustic measures of F0, relative average perturbation (RAP), shimmer, noise-toharmonic ratio (NHR), voice turbulence index (VTI), and SPL, and the aerodynamic measure of voice airflow. Questionnaires. Self-reported information is often applied in studies that involve behavior change because it generates prompt and reliable results in investigations involving behavior estimation and modification.28,55 In this study, self-reported data were collected primarily to describe participants and alternatively as an attempt to understand possible associations among voice usage and voice performance. The VHI56 was developed to estimate feelings and limitations attributed to voice usage to enlighten voice production from the speaker’s perspective by gauging impressions regarding the effects of three broad aspects associated with voice use: functional, physical, and emotional.56 Although trained singers may not present a voice handicap, the VHI was used as an attempt to examine psychosocial aspects of voice usage with the application of a widely used standardized method. The VPS, designed for this study, included demographic data, in addition to questions related to vocal behavior, incidence of vocal fatigue symptoms, and general knowledge of voice care (Appendix). Procedures The participants were tested individually three separate times, equally distributed at the beginning, middle, and end of the academic semester (ie, first, eighth, and 15th weeks). All data were recorded in digital files and text files listing summary measures.38 The testing was applied to one participant per test day, beginning at 8 AM. On arriving, participants received instructions regarding the study and signed an informed consent form for participation. Next, they were asked to report voice-related habits and feelings by responding to the two questionnaires, VPS and VHI. Participants then (a) had their voice tested using the SIUC Voice Lab equipment (ie, CSL and PAS) and (b) wore the APM from 8:30 AM to 3:30 PM during a typical school day including singing lessons and related activities, representing a consistent timeframe associated with routine and activities attended by all participants involved in the study. Efforts to ensure measurement reliability included systematic methods applied in all trials, following procedures described in the literature by authorities44,57,58 as well as manufacturer’s guidelines.37–39 The microphone used to capture acoustic parameters in the voice laboratory was placed on a stand for stability at a distance of 10 cm from the lips at an angle of 45 to reduce aerodynamic noise from the mouth during speech.44 Additionally, each participant was instructed to stabilize the PAS external ergonomic device by
3
holding the bilateral handles while placing the mask firmly against their face, covering the entire mouth and nose.39 Five averaged repetitions of each voice laboratory assessment were recorded in an attempt to obtain reliable measures.57–59 Data collection for acoustic (ie, RAP, shimmer, NHR, and VTI) and aerodynamic (ie, airflow) measures involved the sustained vowel /a/. To control the variability of fundamental frequency and intensity across speech sound tokens, each participant was instructed to produce the vowel /a/ naturally (ie, without using vibrato) at a habitual pitch and loudness level for 5 seconds.60 The speech sound period extending from 1.0 to 3.0 second from onset of each utterance was then extracted for analysis. Calibration of instruments before data collection was conducted according to manufacturer’s instructions.37–39 Utterances for acoustic analysis were captured using the MDVP module of the CSL, a multiparameter acoustic analysis tool which acquires, analyzes, and displays voice parameters from vocalizations, such as RAP, shimmer, NHR, and VTI. Aerodynamic analysis focused on mean expiratory airflow, using the Comfortable Sustained Phonation protocol, the PAS. Objective data were also obtained from continuous voicing produced during a regular day, throughout a period of 7 hours, with the use of the APM. Experimental design General effects of SVD were examined with the application of one-way within-participants analysis of variances (ANOVAs) with repeated measures to data collected in three separated times equally distributed in the course of an academic semester to investigate the impact of cumulative demands on voice. Each participant served as self-control, keeping individual differences constant throughout the experiment.59 Additional comparisons using univariate ANOVAs involving F0 and intensity measures from the CSL and APM were conducted as an introductory attempt to understand vocal behavior in diverse settings and tasks. These exploratory analyses were performed with basis on similarities among acoustic principles used in the design of both instruments,37–39,60,61 despite the diversity of environments and equipment. Furthermore, because a change in the level of significance will affect the risk for both Type I and Type II error, the traditional alpha level of .05 was selected for all behaviors in this study.62–64 RESULTS This investigation involved four female and four male college students majoring in voice who provided voice acoustic and aerodynamic data. Averaged statistical profiles generated by laboratorial voice instruments were applied in statistical comparisons using SPSS software version 20.0 (IBM Corp, Armonk, NY). Results related to the effect of cumulative voice demands on voice parameters of student singers were analyzed with the application of ANOVAs. Descriptive statistics and normative data from all voice parameters measured in this study are included on Table 1. Statistical comparisons demonstrating comparisons across successive time samples are described as follows.
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Journal of Voice, Vol. -, No. -, 2014
TABLE 1. Descriptive Statistics Overall
N
M1
SD 1
M2
SD 2
M3
SD 3
M Total
SD Total
RAP Shimmer NHR VTI SPL (CSL) Airflow SPL (APM)
8 8 8 8 8 8 8
0.605 3.103 0.131 0.046 55.691 0.600 69.636
0.656 0.945 0.012 0.010 4.324 0.349 6.462
0.553 2.910 0.116 0.046 54.397 0.546 106.683
0.540 1.070 0.025 0.009 2.744 0.303 84.536
0.370 3.262 0.124 0.057 54.790 9.782 76.822
0.208 1.021 0.024 0.023 4.768 26.352 5.871
0.509 3.092 0.124 0.050 54.959 0.549 84.339
0.493 0.980 0.021 0.016 3.899 0.287 9.699
Males
N
NT*
M1
SD 1
M2
SD 2
M3
SD 3
M Total
SD Total
F0 (CSL) RAP Shimmer NHR VTI SPL (CSL) Airflow F0 (APM) SPL (APM)
4 4 4 4 4 4 4 4 4
132* 0.78* 3.81y 0.19y 0.006y 77.80z 0.133x 131* 77.80z
148.185 0.505 3.172 0.140 0.041 55.830 0.687 162.585 67.602
36.873 0.430 0.584 0.007 0.012 61.183 0.381 39.944 4.372
146.865 0.245 2.542 0.135 0.051 53.355 0.600 186.062 79.142
24.700 0.156 0.682 0.009 0.011 2.765 0.381 25.693 5.295
138.068 0.315 2.900 0.134 0.065 54.295 0.497 174.725 75.280
33.125 0.205 0.515 0.029 0.024 6.341 0.286 26.565 4.152
144.373 0.355 2.872 0.136 0.052 54.493 0.595 174.457 74.008
29.299 0.286 0.604 0.016 0.018 4.961 0.329 30.131 6.531
Females
N
NT*
M1
SD 1
M2
SD 2
M3
SD 3
M Total
SD Total
F0 (CSL) RAP Shimmer NHR VTI SPL (CSL) Airflow F0 (APM) SPL (APM)
4 4 4 4 4 4 4 4 4
224* 0.63* 3.81y 0.19y 0.006y 74.00z 0.133x 217* 74.00z
249.105 0.704 3.034 0.122 0.051 55.552 0.512 288.645 71.670
39.231 0.890 1.313 0.010 0.007 2.311 0.345 28.955 8.202
261.725 0.861 3.277 0.097 0.041 55.440 0.492 296.232 134.225
56.665 0.635 1.359 0.020 0.005 2.651 0.248 77.090 120.930
264.586 0.426 3.624 0.114 0.050 55.285 0.505 276.367 78.117
57.330 0.226 1.349 0.016 0.022 3.491 0.195 50.058 7.567
258.472 0.664 3.312 0.111 0.047 55.425 0.503 287.078 94.670
47.341 0.612 1.239 0.018 0.013 2.590 0.244 51.048 69.880
Abbreviations: M, mean; NT*, normative threshold; SD, standard deviation. * Colton et al (2011).53 y KayPENTAX (2008).39 z Hillman & Kobler (1999).68 x Zraick et al (2011).69
Voice laboratory acoustic parameters Comparisons involving voice laboratory acoustic parameters described in the research questions were not found to have statistical significance. Acoustic results were RAP F(2, 14) ¼ 1.022, P ¼ 0.385; shimmer F(2, 14) ¼ 0.449, P ¼ 0.647; NHR F(2, 14) ¼ 1.950, P ¼ 0.179, VTI F(2, 14) ¼ 1.709, P ¼ 0.217; SPL F(2, 14) ¼ 0.193, P ¼ 0.826 (Table 2). Aerodynamic parameters Additionally, comparisons involving airflow measurements did not reveal statistically significant results: F(2, 14) ¼ 0.988, P ¼ 0.397 (Table 3). Further analyses using participants grouped by gender also did not to lead to statistically significant changes. APM parameters Comparisons related to F0 and SPL collected during 7 hours did not reach statistically significant results. F0 and SPL results were F0 F(2, 14) ¼ 1.265, P ¼ 0.313; SPL F(2, 14) ¼ 1.442, P ¼ 0.269 (Table 4).
Comparisons of measures collected using voice laboratory and ambulatory monitoring materials Comparisons involving parameters collected using diverse materials and tasks were conducted as an exploratory attempt to further analyze vocal behaviors in student singers. F0 and SPL measures obtained from laboratorial and ambulatorial materials were compared using ANOVAs. Results revealed statistically significant differences in F0 (F0 F(1, 23) ¼ 13.077, P ¼ 0.000) but not in SPL (SPL F(1, 23) ¼ 0.767, P ¼ 0.622; Table 5). Overall, participants tended to use higher F0 and SPL in natural conditions.
Sex-specific results Subsequent examination of data revealed statistical significance associated with NHR measured in females: F(2, 6) ¼ 9.253, P ¼ 0.015. Additionally, SPL measured using ambulatory monitoring demonstrated significant differences in males F(2, 6) ¼ 5.307, P ¼ 0.047 (Table 6).
Maria Claudia Franca and Jeanine F. Wagner
TABLE 2. Singing Vocal Demands (SVD) on Voice Laboratory Acoustic Parameters: Repeated Measures Parameter
Sum of Squares
F0 Within 127.810 participants Error 16 566.663 RAP Within 0.243 participants Error 1.661 Shimmer Within 0.499 participants Error 7.766 NHR 0.001 Within participants Error 0.004 VTI Within 0.001 participants Error 0.003 SPL Within 7.040 participants Error 254.857
df 2
Mean Square
F
TABLE 4. Singing Vocal Demands (SVD) on APM Parameters: Repeated Measures Sig.
63.905 0.054 0.948
14 1183.333 2 14 2 14 2 14 2 14 2 14
0.121 1.022 0.385 0.119 0.249 0.449 0.647
0.000 1.950 0.179 0.000 0.000 1.709 0.217 0.000 3.520 0.193 0.826 18.204
Questionnaires Participants completed the VPS and the VHI questionnaires when having the first voice measurement. Approximately 50% of the participants reported that they sometimes use their voice with excessive effort; 25% of the participants reported having occasional to frequent symptoms of hoarseness and sore throat. In general, the participants indicated knowledge of voice care as suggested by reports of following systematic vocal warm-up techniques (100%), maintaining adequate body hydration (90%), avoiding environmental and functional vocal stresses involving background noise and laryngeal irritant substances (90%), and resting the vocal mechanism as needed (90%). In addition, 50% of the participants responded that
TABLE 3. Singing Vocal Demands (SVD) on a Voice Laboratory Aerodynamic Parameter: Repeated Measures
Airflow Within participants Error
Parameter
Sum of Squares
df
Mean Square
F
Sig.
SPL Within 6175.610 2 3087.805 1.442 0.269 participants Error 29 973.613 14 2140.972 F0 Within 1608.524 2 804.262 1.265 0.313 participants Error 8901.948 14 635.853 Notes: Computed using alpha ¼ 0.05. Sig., Statistical significance.
0.555
Notes: Computed using alpha ¼ .05. Sig., Statistical significance.
Parameter
5
Vocal Demands on Student Singers
Sum of Squares
df
Mean Square
F
Sig.
452.345
2
226.173
0.988
0.397
3204.493
14
228.892
Notes: Computed using alpha ¼ .05. Sig., Statistical significance.
they would seek professional help when experiencing voicerelated problems. Moreover, none of them were smokers (Table 7). Results from the VHI survey revealed concerns mostly related to physical and functional aspects of voice. The highest VHI scores associated with physical aspects of voice referred to concerns about voice quality variations, whereas functional aspects of voice involved intelligibility and communication effectiveness. DISCUSSION In this study, voice parameters of student singers measured throughout an academic semester were analyzed. The participants were eight college music students majoring in voice, with a range of 4–6 years of formal voice training; four were males and four females. Although some statistically significant differences were found in association with results grouped by sex, negative overall comparisons of acoustic and aerodynamic measures were verified. Complementary self-reported information provided further insight into voice usage among student singers. Responses obtained from both VPS and VHI surveys signaled an overall understanding of the voice mechanism and the need of its preservation, as well as a focus on adequate
TABLE 5. Comparisons Between F0 and SPL in the Voice Laboratory and in Natural Settings Parameter
Sum of Squares
df
Mean Square
F
Sig.
SPL Between 87.915 1 12.559 0.767 0.622 groups Error 261.898 23 16.369 F0 Between 95 514.019 1 13 644.860 13.077 0.000 groups Error 166 994.473 23 1043.405 Notes: Computed using alpha ¼ .05. Sig., Statistical significance.
6
Journal of Voice, Vol. -, No. -, 2014
TABLE 6. Singing Vocal Demands (SVD) on Voice Parameters: SexRelated Statistically Significant Results Parameter NHR females Within participants Error SPL APM males Within participants Error
Sum of Squares
df
Mean Square
0.001
2
0.001
F
Sig.
0.001
9.253
0.015
2
0.001
9.253
0.015
278.727
2
139.364
5.307
0 .047
157.575
6
26.263
Notes: Computed using alpha ¼ .05. Sig., Statistical significance.
usage of voice. It seems like, despite indications of eventual voice fatigue, awareness regarding voice care procedures supported voice stability in this group. These essentially negative results may imply that previous voice training may support vocal health, particularly in light of a previous similar study encompassing a population allegedly not trained in voice techniques.29 The aforementioned investigation, conducted with a population of student teachers using materials, procedures, and variables identical to this study, led to results that suggest that in a group of preprofessional voice users with no prior formal voice training, cumulative vocal demands that take place through a typical academic semester resulted in actual deterioration of most voice parameters investigated (ie, F0, RAP, shimmer, and NHR in the voice laboratory, and SPL in ambulatory conditions). In addition, responses from identical questionnaires (ie, VPS and VHI) applied to student teachers revealed a general reduced awareness regarding voice care among
student teachers, which may have a connection with changes indicating progressive instability in that population, in the course of an academic semester. These discrepancies between results from preprofessional groups being prepared to use the professional voice in two diverse areas (ie, singing and teaching) hint that formal voice training is supportive to voice stability and quality. It is important to consider that singers may belong to a group whose vocal physiology is somehow resistant because of innate characteristics and training.32 Nevertheless, these results corroborate views that indicate that singers, as elite professional voice users, have an appreciation for a general state of health that contribute to their work performance, as evidenced by the self-report data.65 Overall, both male and female participants used higher F0 and SPL in circumstances related to academic environments, which may be simply due to specific needs essentially pertinent to singing performance. It is critical to note that comparisons among samples collected in diverse conditions were conducted in an effort to clarify contrasting behaviors associated with voice production in diverse situations. Despite the limitations involved in attempting to compare measures obtained from different tasks, settings, and equipment and thus subjected to influences of factors such as diverse microphone signal and acoustic environment issues,44,63,66 these results may help in providing future research directions for proper comparisons. Although it was not the focus of this study to analyze all single possibilities, it is interesting to observe that not every outcome was consistent with the majority of data. Although supported by systematic procedures, the method did not create similar results in every participant. For example, the male who exhibited the largest overall perturbation values (ie, participant 1) reported having frequent voice symptoms such as hoarseness, sore throat, and persistent throat cleaning, despite
TABLE 7. Summary of the VPS Responses Component Gender Age Educational degree Voice training Typical environment, loudness, and pitch of voice usage Estimated hours per day speaking Smokers Drink at least four glasses of water a day Self-reported voice problems
Self-reported voice care
Description Four females, four males Range: 22–34 y; mean: 26 y Eight participants holding a bachelor’s degree Range: 4–6 y Home and school Range: 2–12 0 8 Hoarseness: two participants Voice loss: two participants Sore throat: two participants Voicing effort: three participants Regular vocal warming: eight participants Regular adequate body hydration: seven participants Avoid competition with background noise: seven participants Avoid smoky environments: seven participants Take voice breaks: seven participants Would see a doctors as needed: four participants
Maria Claudia Franca and Jeanine F. Wagner
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Vocal Demands on Student Singers
TABLE 8. Individual Values Part
Gender
Month
F0 CSL
RAP
Shimmer
NHR
VTI
SPL CSL
Airflow
F0 APM
SPL APM
1 1 1 2 2 2 3 3 3 4 4 4 5 5 5 6 6 6 7 7 7 8 8 8
Male Male Male Female Female Female Female Female Female Male Male Male Female Female Female Male Male Male Female Female Female Male Male Male
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
139.080 143.814 109.555 222.946 325.064 336.277 288.949 293.412 283.359 185.578 175.695 110.383 275.818 221.354 231.119 100.892 115.844 174.331 208.707 207.070 207.591 167.190 152.109 158.005
1.111 0.464 0.232 0.545 0.319 0.428 0.126 0.818 0.339 0.518 0.142 0.153 0.139 0.546 0.202 0.203 0.252 0.616 2.008 1.764 0.735 0.191 0.122 0.261
3.889 2.068 2.928 3.255 2.616 3.428 1.674 1.700 1.849 3.411 1.925 2.763 2.453 4.632 5.015 2.717 3.402 2.335 4.754 4.163 4.206 2.674 2.775 3.577
0.144 0.130 0.109 0.123 0.097 0.104 0.110 0.068 0.104 0.145 0.135 0.144 0.123 0.109 0.113 0.143 0.148 0.112 0.135 0.114 0.138 0.130 0.127 0.171
0.052 0.037 0.064 0.046 0.040 0.026 0.044 0.036 0.039 0.025 0.047 0.064 0.058 0.041 0.058 0.039 0.060 0.036 0.056 0.049 0.078 0.051 0.060 0.097
56.100 54.350 51.620 52.430 53.010 59.900 56.600 55.470 56.080 64.370 56.790 50.490 57.820 59.120 52.620 52.630 51.550 63.780 55.360 54.160 52.540 50.220 50.730 51.290
0.990 1.150 0.520 0.340 0.430 0.570 1.030 0.860 0.750 1.020 0.540 0.180 0.320 0.340 0.380 0.500 0.430 0.870 0.360 0.340 0.320 0.240 0.280 0.420
168.060 176.390 175.210 264.860 286.460 266.490 296.050 306.260 327.290 199.260 218.180 199.020 267.140 202.210 211.210 105.990 157.470 137.640 326.490 390.000 300.480 177.030 192.210 187.030
68.570 75.260 79.590 67.640 78.300 75.490 62.340 68.130 70.520 65.150 78.150 69.870 76.190 74.960 77.990 63.380 86.880 74.550 80.510 315.510 88.470 73.310 76.280 77.110
indications of awareness and application of habitual voice care including proper hydration, use of vocal warm-up exercises, and avoidance of voice irritating environmental components. Likewise, the female (ie, participant 7) who demonstrated the largest perturbation values reported similar voice disturbances, in spite of following common vocal hygiene techniques (Table 8). These incidences may be explained in part by the fact that participants 1 and 7 reported having seasonal and occasional allergy symptoms. Furthermore, it is interesting to note that only 50% of the subjects indicated that they would seek professional help should they experience vocal difficulties. Finally, in addition to previously raised concerns regarding possible inherent characteristics of participants and implications of results generated during ambulatory monitoring, findings need to be interpreted with caution because they derived from a limited sample. The present study used participants who belong to a specific environment of voice usage, as a manner of obtaining experimental control by avoiding confounding factors caused by extraneous variables.61,67 Furthermore, concerns regarding accuracy of self-reported information were addressed by emphasizing confidentially of results and stressing the importance of generating precise scientific data to implement future plans in voice care.65
CONCLUSIONS This study attempted to underline the importance of clarifying and quantifying the relationship of vocal demands and voice performance among student singers. Results apply to both
educational aspects of vocal health and the development of preventive measures for voice disorders in student singers as well as in professional and preprofessional voice users in general. Elite occupational voice users such as singers should be provided with quality information regarding voice care.18,26,65 To propose effective plans to prevent voice disorders in occupational voice users, including singers, it is important to understand aspects of their vocal behavior. This study attempted to identify vocal behavior of student singers by examining vocal acoustics and aerodynamics throughout an extended period with laboratory acoustic and aerodynamic-oriented equipment (ie, CSL, PAS). Additionally, following a growing trend of interest in applying devices for monitoring body systems while individuals perform natural daily activities, this study used a portable device that collects objective data throughout extended periods (ie, APM).19,38 Self-reported data surveyed as supplementary information regarding voice-related aspects from the participants’ standpoint56 seemed to substantiate indications of voice stability in this population, apparently in association with extensive formal training. Additional results of this investigation, conveying the relationship between direct APM measures and vocal acoustics and aerodynamics measured by the CSL and the PAS, indicated different vocal behaviors in the voice laboratory and during ambulatory monitoring that could be due to performancerelated needs. It is hoped that the results of this study help in clarifying the importance of education and awareness about vocal health. It is also hoped that this study will inspire extended investigations to
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