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Effectiveness of a Voice Training Program for Student Teachers on Vocal Health
Effectiveness of a Voice Training Program for Student Teachers on Vocal Health Bernhard Richter, Manfred Nusseck, Claudia Spahn, and Matthias Echternach, Freiburg, Germany Summary: Objectives. The effectiveness of a preventive training program on vocal health for German student teachers was investigated on specific vocal parameters. Methods. The voice quality as described by the Dysphonia Severity Index of 204 student teachers (training group: n ¼ 123; control group: n ¼ 81) was measured at the beginning and at the end of the student teachers training period (duration 1.5 years). Additionally, for investigating the voice-carrying capacity, a vocal loading test (VLT) was performed. Finally, participants had to provide a subjective judgment of a possible Voice Handicap Index. Results. The training program improved the voice quality of the trained group compared with that of the control group, whose voice quality declined. The trained group was also able to better sustain their voice quality across the VLT than the control group. Both groups, however, reported a similar increase in subjective vocal strain. Conclusions. The presented training program clearly showed a positive impact on the voice quality and the vocal capacity. The results maintain the importance of such a training program to be integrated in the education and occupational routine of teachers. Key Words: Voice–Teachers–Vocal health–Vocal loading–Prevention.
INTRODUCTION The voice is an essential tool in the teaching profession. It is not only necessary to impart knowledge but also to communicate emotions and personal characteristics. Hence, vocal problems have direct consequences on the teaching abilities. Studies showed that teachers with vocal disorders had a negative influence on the pupils’ learning outcome.1,2 It is therefore important that teachers maintain a good vocal function during their professional life. Teachers, however, often experience voice disorders, and it has been shown that they are at greater risk for developing voice disorders compared with those in other professions.3–5 On average, up to 50% of teachers complained about having experienced a serious vocal problem at least once in their teaching career.6–9 Furthermore, the onset of voice problems is not only limited to older teachers with years of working experience. Younger teachers may also experience voice complaints within the first few years of teaching. Simberg10 showed that 39% of student teachers reported voice symptoms. Nevertheless, prevalence of reported voice problems in teachers largely ranges between 5% and 90%. This variety depends mostly on different definitions of voice problem and how it was reported.4 To prevent vocal problems, various voice training programs have been developed. For example, on the basis of the concept of the Schlaffhorst-Anderson method, Saatweber11 published several practical exercises for teachers’ voices. Other voice programs for teachers focused on group training and were
Accepted for publication May 6, 2015. From the Freiburg Institute of Musicians’ Medicine, University of Music and University Medical Center, Freiburg, Germany. Address correspondence and reprint requests to Bernhard Richter, Freiburg Institute of Musicians’ Medicine, University of Music and University Medical Center, Breisacher Str. 60, 79106 Freiburg, Germany. E-mail: [email protected] Journal of Voice, Vol. -, No. -, pp. 1-8 0892-1997/$36.00 Ó 2015 The Voice Foundation http://dx.doi.org/10.1016/j.jvoice.2015.05.005
methodologically divided into an ‘‘indirect’’ training (including lectures about the functionality of and influences on the voice) and a ‘‘direct’’ training (with personal coaching and practical exercises). Several studies investigated the effects of these training methods on voice aspects. Timmermans et al12 found that students (n ¼ 49) who participated in 9 months of voice training (indirect and direct) showed a positive effect on the quality of the voice described by the Dysphonia Severity Index (DSI13) compared with a group without voice training (n ¼ 20). The trained group obtained a significantly higher DSI of 4.3 than the control group (DSI of 3.2). Additionally, they used the self-assessment questionnaire for vocal symptoms, the Voice Handicap Index (VHI14), and found that both groups scored similarly. In a follow-up study, Timmermans et al15 investigated another short voice training program (6 hours) in future teachers and found no significant effects of the DSI and the VHI between the trained group (n ¼ 35) and the control group (n ¼ 30). Even with an addition of 30 minutes of individual voice counseling, no significant changes could be observed.16 Duffy and Hazlett17 compared two groups of student teachers with voice programs of either indirect (n ¼ 20) or direct (n ¼ 12) voice training with a control group without training (n ¼ 23). The results showed no differences in the mean values of the VHI. Measuring the DSI, they found an increase for the direct voice training group, no difference for the indirect group, and a decrease for the control group. The results, however, did not reach statistical significance. Similarly, Bovo et al18 investigated kindergarten teachers with indirect and direct training (n ¼ 21) compared with matched untrained persons (n ¼ 20). They found large positive effects in several acoustic voice parameters (such as maximum phonation time (MPT), jitter, and shimmer) and in the VHI. These effects still remained in a 12-month retest but were slightly reduced.
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TABLE 1. Content of Each Session of the Voice Training Program Session
Topic
1 2 3 4 5 6 7 8 9 + 10 Always
Voice hygiene and voice functioning Movement and postural alignment Breathing behavior Finding the individual pitch during speaking Vocal intensity Resonance and cavities Articulation Prosodic elements Recaps and presence Care packet
As there are several more publications on this subject, two literature reviews on the effectiveness of voice trainings have been performed. Ruotsalainen et al19 selected, out of a body of over 5000 references, only two studies that confirmed the criteria required, such as homogenous population, study design, and measurements performed. The amount increased up to six studies in a later repeated review but they could not find evidence for the effectiveness of voice training in improving vocal function.20 Hazlett et al21 performed a similar review with 10 studies included. They also found no clear evidence for positive effects of voice training and concluded, as there have been studies showing that voice training did improve aspects of the quality of the voice, that more robust research should be performed. Both reviews criticized that the methodological quality in most of the studies was poor mainly because of rather small sample sizes, nonrandomized designs, the large diversity of training programs (content, length in time, and amount of sessions), and the rather short time between training and follow-up measurements, which should be at least 1 year.20 Since these reviews, several studies addressing the topic have been published. Nanjundeswaran et al,22 for instance, investigated the effects of two different training programs (indirect and indirect combined with direct) in student teachers (n ¼ 31) on the VHI value compared with a control group. They found a decrease of the VHI in both trained groups. For the subjects with low VHI values at the beginning, however, the VHI increased. Because of the small sample size, they only described the positive effect of the training. Pizolato et al23 measured acoustic parameters of the voice
to analyze effects between a group of teachers with vocal training (n ¼ 30) and a control group (n ¼ 43). They found that the fundamental frequency (F0) of the trained male participants decreased but increased in the trained female participants. There were no significant differences of both groups between the initial and final measurements after 3 months, except that only the control group increased their mean voice intensity. Regarding all these studies, there is still no clear evidence of the positive effects of voice training on vocal functioning. The aim of this study was to analyze vocal outcome of a prevention training program on vocal health in a homogenous sample with a larger sample size (n ¼ 204 German student teachers). It was hypothesized that vocal function was improved for subjects getting vocal training within the prevention program, where vocal function was impaired for those who had no such voice training. MATERIALS AND METHODS Voice training protocol The training program was integrated into the teaching education period for student teachers (duration 1.5 years). It was set to eight sessions of 90 minutes during the first half year of the education period, two refreshing sessions of 90 minutes in the second half year, and an individual teacher observation at school for all participants of the intervention group by the voice teachers in the last half year. The individual voice topics of the training of all sessions are listed in Table 1. Each session included the so-called ‘‘care packet.’’ This is a short program that can be performed in <10 minutes containing selected exercises of all topics such as body stretching, jaw massage, breathing, activating the articulation, and pronouncing syllables. It was designed as a repeatable procedure across the whole training program and to be used to activate the voice and the body before a working day or a voice-demanding situation. The courses were given at the institutions where the seminars for the teaching education period took place. They were organized in groups of 10–12 people and were led by professionally educated voice teachers. Participants The sample of the study comprised a total of 266 vocally healthy student teachers, who just started with their education
FIGURE 1. Study design and number of participants at both evaluation times.
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Evaluation of a Voice Training Program
TABLE 2. Number of Participants and Gender Distribution for Each School Type School Type
%
Primary school 30 Junior high 21 school High school 35 School for 14 handicapped children Total 100
Intervention Control Gender Group Group (Female, %) 37 25
25 17
87 71
42 19
29 10
63 93
123
81
77
period at that time. They came from four different school types: primary school, junior high school, high school, and school for handicapped children. All subjects gave their agreed consent for participation, approved by the local ethical committee. Before the measurement procedure, all subjects were examined by an experienced otolaryngologist for exclusion because of a vocal dysfunction. In this respect, six possible participants at the pretest were thereby excluded from the sample because of vocal fold pathologies. The assignment into the intervention and control groups was different among the school types. The seminars of the primary and junior high school were organized in classes of 10–12 student teachers. For easier realization of the intervention courses, whole classes were randomly allocated to the intervention group, and in the other classes, the student teachers were asked to participate for the control group. In the other seminars, student teachers were asked for voluntary participation and were afterward randomly assigned into the two groups. After the first measurement at the beginning of the teacher training period, the sample consisted of n ¼ 153 in the intervention group and n ¼ 113 in the control group (Figure 1). The groups have uneven sizes because of the primary intention to fill up the intervention courses. The second measurement was at the end of the training period approximately 9 months after the end of the voice training lessons, that is, half a year after the refreshing lessons and a few weeks after the teaching observation of the voice trainer. At the second measurement, 204 subjects were reevaluated (77%) with a distribution of n ¼ 123 (80%) in the intervention group and n ¼ 81 (72%) in the control group. As repeated-measures tests were used for the statistics, these subjects constituted the database of analysis.
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There were no significant differences between this database and the dropped out participants for gender, age, or school type distribution. The mean age of the student teachers was 27.1 years (standard deviation [SD], 3.6 years) with 26.7 years (SD, 2.8 years) for the intervention group and 27.6 years (SD, 4.2 years) for the control group. Seventy-seven percent (n ¼ 156) were female student teachers. The gender distribution, however, differed between the school types (Table 2) but showed, respectively, representative distributions for each individual school type. Evaluation instruments All subjects were analyzed using a multidimensional voice assessment protocol including videostroboscopy, VHI (the short form of the German version with 12 items was used24), Roughness-Breathiness-Hoarseness scale, and acoustic measures. The highest fundamental frequency (F0 max), the lowest intensity, the jitter (by use of the sustained vowel /a/), and the MPT (best of three attempts) were determined using the lingWAVES software (WEVOSYS, Forchheim, Germany, sound level meter at a distance of 30 cm). From these data, the DSI13 was established. After that, a vocal loading test (VLT) was performed. Here, the subjects were asked to read a standardized text (German Text: Das tapfere Schneiderlein, Grimm brothers) for 10 minutes louder than 80 dB at a distance of 30 cm on the basis of a recommendation by Echternach et al.25 The subjects could see their intensity level on a computer screen, which showed a red arrow when the sound pressure level was below the required 80 dB. The program calculates the mean values of the percentage <80 dB, the fundamental frequency, and the sound pressure level averaged across the recorded 10 minutes. This test was shown to be able to stress the voice equally to a class teaching situation of 45 minutes.26 After the VLT, the DSI measurement was repeated. The measurement procedure for the first and the second measurements is shown in Figure 2. The report of the results is divided into two aspects: (1) the analysis of changes in the voice quality between the first and the second measurements by using the values of the DSI before the VLT (pre-VLT) and (2) changes in the voice-carrying capacity, that is, the differences between the measurements before (pre-VLT) and after the VLT (post-VLT) at both measuring times. Statistics Data were analyzed using the statistic software SPSS 21 (SPSS Inc., Armonk, NY). For the comparison of the
FIGURE 2. Measurement procedure at both the first and the second measurements.
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TABLE 3. Mean Values of the Different Voice Parameters and the VHI at Both Measurements Before the Vocal Loading Test Intervention Group (n ¼ 123) Measurement F0 max females (Hz) F0 max males (Hz) Lowest intensity (dB) Jitter (%) MPT (s) DSI (diff. first/second) VHI
Control Group (n ¼ 81)
First
Second
First
Second
718 (159) 492 (183) 53.9 (4.4) 0.19 (0.2) 15.9 (4.9)
742 (202) 509 (185) 53.1 (3.9) 0.19 (0.2) 16.7 (5.4)
739 (149) 473 (146) 52.8 (4.6) 0.18 (0.1) 17.1 (6.2)
732 (183) 463 (150) 53.8 (3.7) 0.20 (0.2) 17.7 (6.4)
6.5 (4.7)
6.2 (4.2)
0.22 (1.35)
+0.25 (1.35) 5.7 (4.5)
6.7 (4.1)
Abbreviations: F0, fundamental frequency; MPT, maximum phonation time; DSI, Dysphonia Severity Index; VHI, Voice Handicap Index. Note: Standard deviation values are given in brackets.
mean values between the intervention and the control groups at the two measuring times, a two-way analysis of variance repeated-measures test with factors of time and group was used. Individual effects of time and group as well as the interaction between both factors were reported. Tests for individual group comparisons were investigated using independent t tests. The level of significance was set on P ¼ 0.05. RESULTS Vocal quality To analyze the effectiveness of the training program on the general voice quality, individual acoustic parameters and the composed value of the DSI before the VLT (pre-VLT) were compared between the first measurement at the beginning and the second measurement at the end of the student teachers training period. Mean values of the parameters are summarized in Table 3. The statistical analyses of time, group, and interaction effects are listed in Table 4. The maximal fundamental frequency (F0 max) was analyzed separately for each gender and yielded no significant effects of time, group, or interaction. The lowest intensity showed a significant interaction effect. There were no significant effects for the jitter. The MPT showed a significant time effect with
an increase of the phonation time at the second measurement for both groups. The DSI, however, yielded a clear significant interaction effect between both groups with an increase of the DSI in the intervention group and a decrease in the control group (Figure 3). The VHI showed a significant time effect with an increase at the second measurement in both groups. In the first measurement, 73% of the participants were below the threshold of a mild voice handicap (<7) according to Nawka et al,24 and the mean value was significantly lower than the threshold value [t(203) ¼ 3.623; P < 0.001]. The number of participants below this threshold reduced to 66% in the second measurement, and the mean value was not significantly different to the threshold value anymore [t(203) ¼ 1.291; P ¼ 0.198]. Voice-carrying capacity The mean values of the outcome parameters of the VLT are listed in Table 5, and the statistical analyses are summarized in Table 6. All parameters showed significant effects between the first and the second measurements without significant group or interaction effects. As the DSI was measured before (pre-VLT) and after the VLT (post-VLT), for all acoustic parameters of the DSI, the
TABLE 4. Statistical Analyses of the Voice Parameters at Both Measuring Times Before the Vocal Loading Test (Table 3) on Time, Group (IG/CG), and Time 3 Group Interaction Effects Measurement F0 max females (Hz) F0 max males (Hz) Lowest Intensity (dB) Jitter (%) MPT (s) DSI (diff. first/second) VHI
Time Effect (First/Second Measurement)
Group Effect (IG/CG)
Time 3 Group Interaction Effect
F(1,154) ¼ 0.417; P ¼ 0.520 F(1,46) ¼ 0.049; P ¼ 0.825 F(1,202) ¼ 1.804; P ¼ 0.181 F(1,202) ¼ 0.447; P ¼ 0.504 F(1,202) ¼ 4.879; P ¼ 0.028 F(1,202) ¼ 0.023; P ¼ 0.880 F(1,202) ¼ 7.651; P ¼ 0.006
F(1,154) ¼ 0.046; P ¼ 0.830 F(1,46) ¼ 0.416; P ¼ 0.522 F(1,202) ¼ 0.132; P ¼ 0.717 F(1,202) ¼ 0.000; P ¼ 0.990 F(1,202) ¼ 2.090; P ¼ 0.150 F(1,202) ¼ 0.601; P ¼ 0.439 F(1,202) ¼ 0.323; P ¼ 0.571
F(1,154) ¼ 1.478; P ¼ 0.226 F(1,46) ¼ 0.668; P ¼ 0.418 F(1,202) ¼ 3.988; P ¼ 0.047 F(1,202) ¼ 0.266; P ¼ 0.635 F(1,202) ¼ 0.088; P ¼ 0.767 F(1,202) ¼ 5.782; P ¼ 0.017 F(1,202) ¼ 0.196; P ¼ 0.658
Abbreviations: F0, fundamental frequency; MPT, maximum phonation time; DSI, Dysphonia Severity Index; VHI, Voice Handicap Index. Note: Interaction effects (in bold: P < 0.05).
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FIGURE 3. Dysphonia Severity Index (DSI) differences between the first and second measurements of both groups (Error bars present the standard error of the mean, *P < 0.05). difference between these two tests was calculated at the first and the second measurements (Table 7). The value of the pre-VLT was subtracted from the value of the post-VLT. Therefore, negative values indicate that the value after the VLT was lower than the one before the VLT. The statistical analyses of the time, group, and interaction effects are listed in Table 8. After the VLT, the participants increased the mean highest F0 except for the male participants in the intervention group who showed lower values in F0 in the first measurement. Nevertheless, there were no significant effects of time, group, or interaction on F0. All participants showed an increase in the lowest intensity after the VLT. The intervention group, however, was able to significantly compensate this loss of soft phonation capacity better in the second measurement than the control group. There were no significant effects for the jitter. MPT was significantly different between the two groups and showed a significant time effect with larger difference values at the second measurement. For the DSI, both groups lost on average 0.5 in value after the VLT in the first measurement. When the control group showed a similar decrease at the second measurement, the intervention group was able to rather keep the DSI level and significantly reduced the difference value (Figure 4).
DISCUSSION A prevention training program on vocal health for German student teachers was evaluated for effects on parameters of vocal functioning and self-perceived voice handicap. The duration between the intervention program and the second measurement was in the recommended range by Ruotsalainen et al.20 The analysis of the vocal quality showed that the DSI increased between the first and second measurements for the trained group and decreased for the control group with significant interaction effect. This finding evidently determines that the voice training had a clear positive effect on the voice quality. The DSI value differences between the first and second measurements were lower compared with the findings of Timmermans et al,12 whereas in their study, the control group also increased in the DSI value. This could be due to the fact that their DSI values in the initial evaluation were, in both groups, notably lower compared with the values of this study. Regarding the different vocal acoustic parameters, there was no effect of the intervention on the jitter, which is in agreement with earlier findings.12,15,23 MPT, however, showed a significant effect between the first and second measurements in both groups with longer MPT in the second measurement. Descriptively, a similar observation was also found by Timmermans et al.12 It seems that the intensive use of the voice and the frequent speaking during the student teacher education period could be seen as a form of training. Because longer MPT indicates a more effective transformation of subglottic pressure to air pulses through the vibrating vocal folds, this might be considered as criteria for enhanced vocal functioning. The results of the VLT also showed that for both groups, the values of the MPT were greater (except for the control group in the first measurement) indicating longer phonation times after the vocal stress. The lowest vocal intensity describes the possibility to produce a noticeable sound at the lowest sound pressure level of the voice. This needs a proper use of and connection between respiratory and laryngeal system. The results showed that the control group revealed a lowest intensity higher by 1 dB, whereas the trained group was able to lower the intensity
TABLE 5. Mean Values of the Fundamental Frequencies (F0), the Percentage <80 dB, and the Sound Pressure Level (SPL) During the Vocal Loading Test Intervention Group (n ¼ 123) Measurement F0 females (Hz) F0 males (Hz) SPL <80 dB (%) Mean SPL (dB)
Control Group (n ¼ 81)
First
Second
First
Second
254 (25.2) 165 (19.9) 31.4 (22.7) 81.3 (2.4)
259 (24.6) 167 (17.2) 19.1 (15.1) 82.5 (1.9)
257 (24.3) 163 (29.8) 29.6 (22.9) 81.6 (2.4)
259 (23.8) 170 (24.0) 19.2 (15.2) 82.6 (1.9)
Note: Standard deviation values are given in brackets.
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TABLE 6. Statistical Analyses of the Voice Parameters During the Vocal Loading Test (Table 5) on Time, Group (IG/CG), and Time 3 Group Interaction Effects Measurement F0 females (Hz) F0 males (Hz) SPL <80 dB (%) Mean SPL (dB)
Time Effect (First/Second Measurement)
Group Effect (IG/CG)
Time 3 Group Interaction Effect
F(1,149) ¼ 6.979; P ¼ 0.009 F(1,45) ¼ 7.337; P ¼ 0.010 F(1,196) ¼ 73.166; P < 0.001 F(1,196) ¼ 54.456; P < 0.001
F(1,149) ¼ 0.125; P ¼ 0.724 F(1,45) ¼ 0.009; P ¼ 0.927 F(1,196) ¼ 0.116; P ¼ 0.734 F(1,196) ¼ 0.297; P ¼ 0.587
F(1,149) ¼ 0.905; P ¼ 0.343 F(1,45) ¼ 1.490, P ¼ 0.229 F(1,196) ¼ 0.501; P ¼ 0.480 F(1,196) ¼ 1.954; P ¼ 0.395
Abbreviations: F0, fundamental frequency; SPL, sound pressure level. Note: Interaction effects (in bold: P < 0.05).
by about 1 dB between the first and second measurements with a significant interaction effect. As this parameter showed to have a rather strong influence on the DSI,25 the interaction effect of the DSI may be mainly caused by this factor together with the small increase of the F0 in the trained group. The VHI showed that both groups reported more selfperceived voice handicap indications at the end of the teacher education period (second measurement). The presumptions by Nanjundeswaran et al22 that the VHI would reduce in the trained group and increase in the control group can therefore not be supported by our data. Even more, Timmermans et al12 found that both the trained and the untrained groups significantly reduced the VHI values without interaction effect instead of increasing it. Interestingly, the VHI values contrast with the findings of the voice quality as measured by the DSI where the trained group clearly improved their voice quality. Therefore, the training program seems to have less impact on the impression of having a vocal handicap that arose with teaching and speaking experiences. Nevertheless, the mean values of both groups were still below the threshold indicating a mild voice handicap (<7) according to Nawka et al.24 The VLT was used to investigate the voice-carrying capacity. The participants in both groups managed the
requirements of the VLT in the second measurement better than in the first. They read louder and reduced the percentage of SPL <80 dB remarkably. They also increased the F0 during the VLT. These results lead to the assumption that the student teachers of both groups experienced some sort of vocal training probably through the teaching experiences that improved the use and the behavior during the VLT. Nevertheless, the DSI differences between the pre-VLT and the post-VLT showed a significant interaction effect. The trained group was able to keep the vocal quality over the VLT in the second measurement. Hence, the voice training had a clear effect on the voice-carrying capacity to stand certain vocal demands. In more detail, the most influencing factor seemed to be again the lowest vocal intensity. The trained group was able to perform phonations with recognizable lower intensity than the control group after the VLT. The results of this study have therefore shown that the prevention training program on vocal and mental health positively affected vocal functioning. To indicate the importance of the components in the training program, future researches should investigate effects of specific implements according to the profession and the comparison with other training programs.
TABLE 7. Mean Values of the Acoustic Parameters as a Difference Between Before and After the Vocal Loading Test (VLT) at Both Measurement Times Intervention Group (n ¼ 123) Measurement F0 Diff. females (Hz) F0 Diff. males (Hz) Low. Int. Diff. (dB) Jitter Diff. (%) MPT Diff. (s) DSI Diff.
Control Group (n ¼ 81)
First
Second
First
Second
2.9 (108) 41.6 (92) 2.12 (3.3) 0.06 (0.2) 0.29 (3.1) 0.56 (1.0)
5.3 (100) 2.3 (103) 1.39 (2.9) 0.01 (0.3) 1.1 (4.1) 0.22 (1.0)
15.3 (119) 11.8 (109) 1.99 (3.1) 0.02 (0.2) 0.68 (3.4) 0.50 (.87)
16.8 (128) 3.5 (103) 2.56 (3.4) 0.01 (0.3) 0.37 (3.9) 0.60 (1.0)
Abbreviations: F0, fundamental frequency; MPT, maximum phonation time; DSI, Dysphonia Severity Index. Note: Standard deviation values are given in brackets.
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TABLE 8. Statistical Analysis of the Voice Parameter Differences Before and After the Vocal Loading Test (Table 7) on Time, Group, and Interaction Effects Measurement F0 Diff. females (Hz) F0 Diff. males (Hz) Low. Int. Diff. (dB) Jitter Diff. (%) MPT Diff. (s) DSI Diff.
Time Effect (First/Second Measurement)
Group Effect (IG/CG)
Time 3 Group Interaction Effect
F(1,154) ¼ 0.027; P ¼ 0.871 F(1,46) ¼ 0.649; P ¼ 0.425 F(1,202) ¼ 0.063; P ¼ 0.802 F(1,202) ¼ 2.734; P ¼ 0.100 F(1,202) ¼ 7.237; P ¼ 0.008 F(1,202) ¼ 1.613; P ¼ 0.206
F(1,154) ¼ 0.760; P ¼ 0.385 F(1,46) ¼ 1.573; P ¼ 0.216 F(1,202) ¼ 2.423; P ¼ 0.121 F(1,202) ¼ 0.196; P ¼ 0.658 F(1,202) ¼ 4.164; P ¼ 0.043 F(1,202) ¼ 2.172; P ¼ 0.142
F(1,154) ¼ 0.001; P ¼ 0.973 F(1,46) ¼ 1.542; P ¼ 0.221 F(1,202) ¼ 4.364; P ¼ 0.038 F(1,202) ¼ 0.972; P ¼ 0.325 F(1,202) ¼ 0.185; P ¼ 0.668 F(1,202) ¼ 5.057; P ¼ 0.026
Abbreviations: F0, fundamental frequency; MPT, maximum phonation time; DSI, Dysphonia Severity Index. Note: Interaction effects (in bold: P < 0.05).
CONCLUSIONS In this study, the effectiveness of a prevention training program on vocal health of German student teachers was investigated. The results indicate that the teacher education period for student teachers was experienced as a voice-demanding time and that the participants developed certain voice strategies through teaching practices. The trained group, however, increased not only their voice quality over time but was also able to withstand vocal loading and kept their vocal quality with statistical significance. These results showed the potential of a prevention program for student teachers on their vocal health. The findings should lead to consequences to better inform and train teachers and especially future teachers how to manage with certain work-related voice demands and to provide prevention programs for voice training. It is important to learn more about one’s own voice and to understand its limitations and vocal capacity. Furthermore, voice problems should be taken more seriously, and on repeated appearance, speech experts should be consulted.
FIGURE 4. Dysphonia Severity Index (DSI) differences between pre-VLT and post-VLT at both measurements for both groups (Error bars present the standard error of the mean, *P < 0.05).
Acknowledgments The authors would like to thank Nisma Bux-Cherrat, Juliane Stein-Vogel, Dr. Louisa Traser, and Dr. Sebastian Dippold for providing the measuring procedure and the examinations. Further special thanks go to the heads of the teacher education seminars Prof. M. Frommhold, Ms. M. Neumann, Ms. N. Kr€ankel-Schwarz, and Mr. T. Sachsenheimer for the support in recruiting the student teachers. The study was funded by the Ministry of Science and Arts and the Ministry of Culture, Youth, and Sports in Baden-W€urttemberg. The authors declare no conflict of interest.
REFERENCES 1. Morton V, Watson DR. The impact of impaired vocal quality on children’s ability to process spoken language. Logoped Phoniatr Vocol. 2001;26: 17–25. 2. Rogerson J, Dodd B. Is there an effect of dysphonic teachers’ voices on children’s processing of spoken language? J Voice. 2005;19: 47–60. 3. Roy N, Merrill R, Thibeault S, Gray S, Smith E. Voice disorders in teachers and the general population: effects on work performance, attendance, and future career choices. J Speech Lang Hear Res. 2004;47: 542–551. 4. Cantor Cutiva LC, Vogel I, Burdorf A. Voice disorders in teachers and their associations with work-related factors: a systematic review. J Commun Dis. 2013;46:143–155. 5. Martins RH, Pereira ER, Hidalgo CB, Tavares EL. Voice disorders in teachers. A review. J Voice. 2014;28:716–724. 6. Smith EM, Lemke J, Taylor M, Kirchner HL, Hoffman H. Frequency of voice problems among teachers and other occupations. J Voice. 1998;12: 480–488. 7. de Jong FI, Kooijman PG, Thomas G, Huinck WJ, Graamans K, Schutte HK. Epidemiology of voice problems in Dutch teachers. Folia Phoniatr Logop. 2006;58:186–198. 8. Verdolini K, Ramig LO. Review: occupational risks for voice problems. Logoped Phoniatr Vocol. 2001;26:37–46. 9. Van Houtte E, Claeys S, Wuyts FL, van Lierde K. Voice disorders in teachers: occupational risk factors and psycho-emotional factors. Logoped Phoniatr Vocol. 2012;37:1–10. 10. Simberg S. Prevalence of Vocal Symptoms and Voice Disorders Among Teacher Students and Teachers and a Model of Early Intervention [Doctoral Thesis]. Helsinki, Finland: Department of Speech Sciences, University of Helsinki; 2004. 11. Saatweber M. How to help teachers’ voices. Folia Phoniatr Logop. 2008; 60:288–290.
8 12. Timmermans B, De Bodt M, Wuyts FL, Van de Heyning P. Voice quality change in future professional voice users after 9 months of voice training. Eur Arch Otorhinolaryngol. 2004;261:1–5. 13. Wuyts FL, De Bodt MS, Molenberghs G, et al. The dysphonia severity index: an objective measure of vocal quality based on a multiparameter approach. J Speech Lang Hear Res. 2000;43:796–809. 14. Jacobson B, Johnson A, Grywalski C, Silbergleit A, Jacobson G, Benninger MS. The Voice Handicap Index (VHI): development and validation. Am J Speech Lang Pathol. 1997;6:66–70. 15. Timmermans B, Coveliers Y, Meeus W, Vandenabeele F, Van Looy L, Wuyts FL. The effect of a short voice training program in future teachers. J Voice. 2011;25:191–198. 16. Timmermans B, Coveliers Y, Wuyts FL, Van Looy L. Voice training in teacher education: the effect of adding an individualized microteaching session of 30 minutes to the regular 6-hour voice training program. J Voice. 2012;26:e1–e9. 17. Duffy OM, Hazlett DE. The impact of preventive voice care programs for training teachers: a longitudinal study. J Voice. 2004;18:63–70. 18. Bovo R, Galceran M, Petruccelli J, Hatzopoulos S. Vocal problems among teachers: evaluation of a preventive voice program. J Voice. 2007;12: 705–722. 19. Ruotsalainen J, Sellman J, Lic P, Lehto L, Verbeek J. Systematic review of the treatment of functional dysphonia and prevention of voice disorders. Otolaryngol Head Neck Surg. 2008;138:557–565.
Journal of Voice, Vol. -, No. -, 2015 20. Ruotsalainen JH, Sellman J, Lehto L, Isotalo LK, Verbeek JH. Interventions for preventing voice disorders in adults (review). Cochrane Database Syst Rev. 2010;1–64. 21. Hazlett DE, Duffy OM, Moorhead SA. Review of the impact of voice training on the vocal quality of professional voice users: implications for vocal health and recommendations for further research. J Voice. 2011;25: 181–191. 22. Nanjundeswaran C, Li NY, Chan KM, Wong RK, Yiu EM, VerdoliniAbbott K. Preliminary data on prevention and treatment of voice problems in student teachers. J Voice. 2012;26:816.e1–816.e12. 23. Pizolato RA, Rehder MI, dos Santos Dias CT, de Castro Meneghim M, Ambrosano GA, Mialhe FL, Pereira AC. Evaluation of the effectiveness of a voice training program for teachers. J Voice. 2013;27:603–610. 24. Nawka T, Wiesmann U, Gonnermann U. Validierung des Voice Handicap Index (VHI) in der deutschen Fassung [Validation of the Voice Handicap Index (VHI) in the German Version]. HNO. 2003;51:921–929. 25. Echternach M, Richter B, Traser L, Nusseck M. Ver€anderung der stimmlichen Leistungsf€ahigkeit durch verschiedene Stimmbelastungstests [Change of Vocal Capacity Due to Different Vocal Loading Tests]. Laryngorhinootologie. 2013;92:34–40. 26. Echternach M, Nusseck M, Dippold S, Spahn C, Richter B. Fundamental frequency, sound pressure level and vocal dose of a vocal loading test in comparison to a real teaching situation. Eur Arch Otorhinolaryngol. 2014;271:3263–3268.
INTRODUCTION The voice is an essential tool in the teaching profession. It is not only necessary to impart knowledge but also to communicate emotions and personal characteristics. Hence, vocal problems have direct consequences on the teaching abilities. Studies showed that teachers with vocal disorders had a negative influence on the pupils’ learning outcome.1,2 It is therefore important that teachers maintain a good vocal function during their professional life. Teachers, however, often experience voice disorders, and it has been shown that they are at greater risk for developing voice disorders compared with those in other professions.3–5 On average, up to 50% of teachers complained about having experienced a serious vocal problem at least once in their teaching career.6–9 Furthermore, the onset of voice problems is not only limited to older teachers with years of working experience. Younger teachers may also experience voice complaints within the first few years of teaching. Simberg10 showed that 39% of student teachers reported voice symptoms. Nevertheless, prevalence of reported voice problems in teachers largely ranges between 5% and 90%. This variety depends mostly on different definitions of voice problem and how it was reported.4 To prevent vocal problems, various voice training programs have been developed. For example, on the basis of the concept of the Schlaffhorst-Anderson method, Saatweber11 published several practical exercises for teachers’ voices. Other voice programs for teachers focused on group training and were
Accepted for publication May 6, 2015. From the Freiburg Institute of Musicians’ Medicine, University of Music and University Medical Center, Freiburg, Germany. Address correspondence and reprint requests to Bernhard Richter, Freiburg Institute of Musicians’ Medicine, University of Music and University Medical Center, Breisacher Str. 60, 79106 Freiburg, Germany. E-mail: [email protected] Journal of Voice, Vol. -, No. -, pp. 1-8 0892-1997/$36.00 Ó 2015 The Voice Foundation http://dx.doi.org/10.1016/j.jvoice.2015.05.005
methodologically divided into an ‘‘indirect’’ training (including lectures about the functionality of and influences on the voice) and a ‘‘direct’’ training (with personal coaching and practical exercises). Several studies investigated the effects of these training methods on voice aspects. Timmermans et al12 found that students (n ¼ 49) who participated in 9 months of voice training (indirect and direct) showed a positive effect on the quality of the voice described by the Dysphonia Severity Index (DSI13) compared with a group without voice training (n ¼ 20). The trained group obtained a significantly higher DSI of 4.3 than the control group (DSI of 3.2). Additionally, they used the self-assessment questionnaire for vocal symptoms, the Voice Handicap Index (VHI14), and found that both groups scored similarly. In a follow-up study, Timmermans et al15 investigated another short voice training program (6 hours) in future teachers and found no significant effects of the DSI and the VHI between the trained group (n ¼ 35) and the control group (n ¼ 30). Even with an addition of 30 minutes of individual voice counseling, no significant changes could be observed.16 Duffy and Hazlett17 compared two groups of student teachers with voice programs of either indirect (n ¼ 20) or direct (n ¼ 12) voice training with a control group without training (n ¼ 23). The results showed no differences in the mean values of the VHI. Measuring the DSI, they found an increase for the direct voice training group, no difference for the indirect group, and a decrease for the control group. The results, however, did not reach statistical significance. Similarly, Bovo et al18 investigated kindergarten teachers with indirect and direct training (n ¼ 21) compared with matched untrained persons (n ¼ 20). They found large positive effects in several acoustic voice parameters (such as maximum phonation time (MPT), jitter, and shimmer) and in the VHI. These effects still remained in a 12-month retest but were slightly reduced.
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TABLE 1. Content of Each Session of the Voice Training Program Session
Topic
1 2 3 4 5 6 7 8 9 + 10 Always
Voice hygiene and voice functioning Movement and postural alignment Breathing behavior Finding the individual pitch during speaking Vocal intensity Resonance and cavities Articulation Prosodic elements Recaps and presence Care packet
As there are several more publications on this subject, two literature reviews on the effectiveness of voice trainings have been performed. Ruotsalainen et al19 selected, out of a body of over 5000 references, only two studies that confirmed the criteria required, such as homogenous population, study design, and measurements performed. The amount increased up to six studies in a later repeated review but they could not find evidence for the effectiveness of voice training in improving vocal function.20 Hazlett et al21 performed a similar review with 10 studies included. They also found no clear evidence for positive effects of voice training and concluded, as there have been studies showing that voice training did improve aspects of the quality of the voice, that more robust research should be performed. Both reviews criticized that the methodological quality in most of the studies was poor mainly because of rather small sample sizes, nonrandomized designs, the large diversity of training programs (content, length in time, and amount of sessions), and the rather short time between training and follow-up measurements, which should be at least 1 year.20 Since these reviews, several studies addressing the topic have been published. Nanjundeswaran et al,22 for instance, investigated the effects of two different training programs (indirect and indirect combined with direct) in student teachers (n ¼ 31) on the VHI value compared with a control group. They found a decrease of the VHI in both trained groups. For the subjects with low VHI values at the beginning, however, the VHI increased. Because of the small sample size, they only described the positive effect of the training. Pizolato et al23 measured acoustic parameters of the voice
to analyze effects between a group of teachers with vocal training (n ¼ 30) and a control group (n ¼ 43). They found that the fundamental frequency (F0) of the trained male participants decreased but increased in the trained female participants. There were no significant differences of both groups between the initial and final measurements after 3 months, except that only the control group increased their mean voice intensity. Regarding all these studies, there is still no clear evidence of the positive effects of voice training on vocal functioning. The aim of this study was to analyze vocal outcome of a prevention training program on vocal health in a homogenous sample with a larger sample size (n ¼ 204 German student teachers). It was hypothesized that vocal function was improved for subjects getting vocal training within the prevention program, where vocal function was impaired for those who had no such voice training. MATERIALS AND METHODS Voice training protocol The training program was integrated into the teaching education period for student teachers (duration 1.5 years). It was set to eight sessions of 90 minutes during the first half year of the education period, two refreshing sessions of 90 minutes in the second half year, and an individual teacher observation at school for all participants of the intervention group by the voice teachers in the last half year. The individual voice topics of the training of all sessions are listed in Table 1. Each session included the so-called ‘‘care packet.’’ This is a short program that can be performed in <10 minutes containing selected exercises of all topics such as body stretching, jaw massage, breathing, activating the articulation, and pronouncing syllables. It was designed as a repeatable procedure across the whole training program and to be used to activate the voice and the body before a working day or a voice-demanding situation. The courses were given at the institutions where the seminars for the teaching education period took place. They were organized in groups of 10–12 people and were led by professionally educated voice teachers. Participants The sample of the study comprised a total of 266 vocally healthy student teachers, who just started with their education
FIGURE 1. Study design and number of participants at both evaluation times.
Bernhard Richter, et al
Evaluation of a Voice Training Program
TABLE 2. Number of Participants and Gender Distribution for Each School Type School Type
%
Primary school 30 Junior high 21 school High school 35 School for 14 handicapped children Total 100
Intervention Control Gender Group Group (Female, %) 37 25
25 17
87 71
42 19
29 10
63 93
123
81
77
period at that time. They came from four different school types: primary school, junior high school, high school, and school for handicapped children. All subjects gave their agreed consent for participation, approved by the local ethical committee. Before the measurement procedure, all subjects were examined by an experienced otolaryngologist for exclusion because of a vocal dysfunction. In this respect, six possible participants at the pretest were thereby excluded from the sample because of vocal fold pathologies. The assignment into the intervention and control groups was different among the school types. The seminars of the primary and junior high school were organized in classes of 10–12 student teachers. For easier realization of the intervention courses, whole classes were randomly allocated to the intervention group, and in the other classes, the student teachers were asked to participate for the control group. In the other seminars, student teachers were asked for voluntary participation and were afterward randomly assigned into the two groups. After the first measurement at the beginning of the teacher training period, the sample consisted of n ¼ 153 in the intervention group and n ¼ 113 in the control group (Figure 1). The groups have uneven sizes because of the primary intention to fill up the intervention courses. The second measurement was at the end of the training period approximately 9 months after the end of the voice training lessons, that is, half a year after the refreshing lessons and a few weeks after the teaching observation of the voice trainer. At the second measurement, 204 subjects were reevaluated (77%) with a distribution of n ¼ 123 (80%) in the intervention group and n ¼ 81 (72%) in the control group. As repeated-measures tests were used for the statistics, these subjects constituted the database of analysis.
3
There were no significant differences between this database and the dropped out participants for gender, age, or school type distribution. The mean age of the student teachers was 27.1 years (standard deviation [SD], 3.6 years) with 26.7 years (SD, 2.8 years) for the intervention group and 27.6 years (SD, 4.2 years) for the control group. Seventy-seven percent (n ¼ 156) were female student teachers. The gender distribution, however, differed between the school types (Table 2) but showed, respectively, representative distributions for each individual school type. Evaluation instruments All subjects were analyzed using a multidimensional voice assessment protocol including videostroboscopy, VHI (the short form of the German version with 12 items was used24), Roughness-Breathiness-Hoarseness scale, and acoustic measures. The highest fundamental frequency (F0 max), the lowest intensity, the jitter (by use of the sustained vowel /a/), and the MPT (best of three attempts) were determined using the lingWAVES software (WEVOSYS, Forchheim, Germany, sound level meter at a distance of 30 cm). From these data, the DSI13 was established. After that, a vocal loading test (VLT) was performed. Here, the subjects were asked to read a standardized text (German Text: Das tapfere Schneiderlein, Grimm brothers) for 10 minutes louder than 80 dB at a distance of 30 cm on the basis of a recommendation by Echternach et al.25 The subjects could see their intensity level on a computer screen, which showed a red arrow when the sound pressure level was below the required 80 dB. The program calculates the mean values of the percentage <80 dB, the fundamental frequency, and the sound pressure level averaged across the recorded 10 minutes. This test was shown to be able to stress the voice equally to a class teaching situation of 45 minutes.26 After the VLT, the DSI measurement was repeated. The measurement procedure for the first and the second measurements is shown in Figure 2. The report of the results is divided into two aspects: (1) the analysis of changes in the voice quality between the first and the second measurements by using the values of the DSI before the VLT (pre-VLT) and (2) changes in the voice-carrying capacity, that is, the differences between the measurements before (pre-VLT) and after the VLT (post-VLT) at both measuring times. Statistics Data were analyzed using the statistic software SPSS 21 (SPSS Inc., Armonk, NY). For the comparison of the
FIGURE 2. Measurement procedure at both the first and the second measurements.
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TABLE 3. Mean Values of the Different Voice Parameters and the VHI at Both Measurements Before the Vocal Loading Test Intervention Group (n ¼ 123) Measurement F0 max females (Hz) F0 max males (Hz) Lowest intensity (dB) Jitter (%) MPT (s) DSI (diff. first/second) VHI
Control Group (n ¼ 81)
First
Second
First
Second
718 (159) 492 (183) 53.9 (4.4) 0.19 (0.2) 15.9 (4.9)
742 (202) 509 (185) 53.1 (3.9) 0.19 (0.2) 16.7 (5.4)
739 (149) 473 (146) 52.8 (4.6) 0.18 (0.1) 17.1 (6.2)
732 (183) 463 (150) 53.8 (3.7) 0.20 (0.2) 17.7 (6.4)
6.5 (4.7)
6.2 (4.2)
0.22 (1.35)
+0.25 (1.35) 5.7 (4.5)
6.7 (4.1)
Abbreviations: F0, fundamental frequency; MPT, maximum phonation time; DSI, Dysphonia Severity Index; VHI, Voice Handicap Index. Note: Standard deviation values are given in brackets.
mean values between the intervention and the control groups at the two measuring times, a two-way analysis of variance repeated-measures test with factors of time and group was used. Individual effects of time and group as well as the interaction between both factors were reported. Tests for individual group comparisons were investigated using independent t tests. The level of significance was set on P ¼ 0.05. RESULTS Vocal quality To analyze the effectiveness of the training program on the general voice quality, individual acoustic parameters and the composed value of the DSI before the VLT (pre-VLT) were compared between the first measurement at the beginning and the second measurement at the end of the student teachers training period. Mean values of the parameters are summarized in Table 3. The statistical analyses of time, group, and interaction effects are listed in Table 4. The maximal fundamental frequency (F0 max) was analyzed separately for each gender and yielded no significant effects of time, group, or interaction. The lowest intensity showed a significant interaction effect. There were no significant effects for the jitter. The MPT showed a significant time effect with
an increase of the phonation time at the second measurement for both groups. The DSI, however, yielded a clear significant interaction effect between both groups with an increase of the DSI in the intervention group and a decrease in the control group (Figure 3). The VHI showed a significant time effect with an increase at the second measurement in both groups. In the first measurement, 73% of the participants were below the threshold of a mild voice handicap (<7) according to Nawka et al,24 and the mean value was significantly lower than the threshold value [t(203) ¼ 3.623; P < 0.001]. The number of participants below this threshold reduced to 66% in the second measurement, and the mean value was not significantly different to the threshold value anymore [t(203) ¼ 1.291; P ¼ 0.198]. Voice-carrying capacity The mean values of the outcome parameters of the VLT are listed in Table 5, and the statistical analyses are summarized in Table 6. All parameters showed significant effects between the first and the second measurements without significant group or interaction effects. As the DSI was measured before (pre-VLT) and after the VLT (post-VLT), for all acoustic parameters of the DSI, the
TABLE 4. Statistical Analyses of the Voice Parameters at Both Measuring Times Before the Vocal Loading Test (Table 3) on Time, Group (IG/CG), and Time 3 Group Interaction Effects Measurement F0 max females (Hz) F0 max males (Hz) Lowest Intensity (dB) Jitter (%) MPT (s) DSI (diff. first/second) VHI
Time Effect (First/Second Measurement)
Group Effect (IG/CG)
Time 3 Group Interaction Effect
F(1,154) ¼ 0.417; P ¼ 0.520 F(1,46) ¼ 0.049; P ¼ 0.825 F(1,202) ¼ 1.804; P ¼ 0.181 F(1,202) ¼ 0.447; P ¼ 0.504 F(1,202) ¼ 4.879; P ¼ 0.028 F(1,202) ¼ 0.023; P ¼ 0.880 F(1,202) ¼ 7.651; P ¼ 0.006
F(1,154) ¼ 0.046; P ¼ 0.830 F(1,46) ¼ 0.416; P ¼ 0.522 F(1,202) ¼ 0.132; P ¼ 0.717 F(1,202) ¼ 0.000; P ¼ 0.990 F(1,202) ¼ 2.090; P ¼ 0.150 F(1,202) ¼ 0.601; P ¼ 0.439 F(1,202) ¼ 0.323; P ¼ 0.571
F(1,154) ¼ 1.478; P ¼ 0.226 F(1,46) ¼ 0.668; P ¼ 0.418 F(1,202) ¼ 3.988; P ¼ 0.047 F(1,202) ¼ 0.266; P ¼ 0.635 F(1,202) ¼ 0.088; P ¼ 0.767 F(1,202) ¼ 5.782; P ¼ 0.017 F(1,202) ¼ 0.196; P ¼ 0.658
Abbreviations: F0, fundamental frequency; MPT, maximum phonation time; DSI, Dysphonia Severity Index; VHI, Voice Handicap Index. Note: Interaction effects (in bold: P < 0.05).
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FIGURE 3. Dysphonia Severity Index (DSI) differences between the first and second measurements of both groups (Error bars present the standard error of the mean, *P < 0.05). difference between these two tests was calculated at the first and the second measurements (Table 7). The value of the pre-VLT was subtracted from the value of the post-VLT. Therefore, negative values indicate that the value after the VLT was lower than the one before the VLT. The statistical analyses of the time, group, and interaction effects are listed in Table 8. After the VLT, the participants increased the mean highest F0 except for the male participants in the intervention group who showed lower values in F0 in the first measurement. Nevertheless, there were no significant effects of time, group, or interaction on F0. All participants showed an increase in the lowest intensity after the VLT. The intervention group, however, was able to significantly compensate this loss of soft phonation capacity better in the second measurement than the control group. There were no significant effects for the jitter. MPT was significantly different between the two groups and showed a significant time effect with larger difference values at the second measurement. For the DSI, both groups lost on average 0.5 in value after the VLT in the first measurement. When the control group showed a similar decrease at the second measurement, the intervention group was able to rather keep the DSI level and significantly reduced the difference value (Figure 4).
DISCUSSION A prevention training program on vocal health for German student teachers was evaluated for effects on parameters of vocal functioning and self-perceived voice handicap. The duration between the intervention program and the second measurement was in the recommended range by Ruotsalainen et al.20 The analysis of the vocal quality showed that the DSI increased between the first and second measurements for the trained group and decreased for the control group with significant interaction effect. This finding evidently determines that the voice training had a clear positive effect on the voice quality. The DSI value differences between the first and second measurements were lower compared with the findings of Timmermans et al,12 whereas in their study, the control group also increased in the DSI value. This could be due to the fact that their DSI values in the initial evaluation were, in both groups, notably lower compared with the values of this study. Regarding the different vocal acoustic parameters, there was no effect of the intervention on the jitter, which is in agreement with earlier findings.12,15,23 MPT, however, showed a significant effect between the first and second measurements in both groups with longer MPT in the second measurement. Descriptively, a similar observation was also found by Timmermans et al.12 It seems that the intensive use of the voice and the frequent speaking during the student teacher education period could be seen as a form of training. Because longer MPT indicates a more effective transformation of subglottic pressure to air pulses through the vibrating vocal folds, this might be considered as criteria for enhanced vocal functioning. The results of the VLT also showed that for both groups, the values of the MPT were greater (except for the control group in the first measurement) indicating longer phonation times after the vocal stress. The lowest vocal intensity describes the possibility to produce a noticeable sound at the lowest sound pressure level of the voice. This needs a proper use of and connection between respiratory and laryngeal system. The results showed that the control group revealed a lowest intensity higher by 1 dB, whereas the trained group was able to lower the intensity
TABLE 5. Mean Values of the Fundamental Frequencies (F0), the Percentage <80 dB, and the Sound Pressure Level (SPL) During the Vocal Loading Test Intervention Group (n ¼ 123) Measurement F0 females (Hz) F0 males (Hz) SPL <80 dB (%) Mean SPL (dB)
Control Group (n ¼ 81)
First
Second
First
Second
254 (25.2) 165 (19.9) 31.4 (22.7) 81.3 (2.4)
259 (24.6) 167 (17.2) 19.1 (15.1) 82.5 (1.9)
257 (24.3) 163 (29.8) 29.6 (22.9) 81.6 (2.4)
259 (23.8) 170 (24.0) 19.2 (15.2) 82.6 (1.9)
Note: Standard deviation values are given in brackets.
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TABLE 6. Statistical Analyses of the Voice Parameters During the Vocal Loading Test (Table 5) on Time, Group (IG/CG), and Time 3 Group Interaction Effects Measurement F0 females (Hz) F0 males (Hz) SPL <80 dB (%) Mean SPL (dB)
Time Effect (First/Second Measurement)
Group Effect (IG/CG)
Time 3 Group Interaction Effect
F(1,149) ¼ 6.979; P ¼ 0.009 F(1,45) ¼ 7.337; P ¼ 0.010 F(1,196) ¼ 73.166; P < 0.001 F(1,196) ¼ 54.456; P < 0.001
F(1,149) ¼ 0.125; P ¼ 0.724 F(1,45) ¼ 0.009; P ¼ 0.927 F(1,196) ¼ 0.116; P ¼ 0.734 F(1,196) ¼ 0.297; P ¼ 0.587
F(1,149) ¼ 0.905; P ¼ 0.343 F(1,45) ¼ 1.490, P ¼ 0.229 F(1,196) ¼ 0.501; P ¼ 0.480 F(1,196) ¼ 1.954; P ¼ 0.395
Abbreviations: F0, fundamental frequency; SPL, sound pressure level. Note: Interaction effects (in bold: P < 0.05).
by about 1 dB between the first and second measurements with a significant interaction effect. As this parameter showed to have a rather strong influence on the DSI,25 the interaction effect of the DSI may be mainly caused by this factor together with the small increase of the F0 in the trained group. The VHI showed that both groups reported more selfperceived voice handicap indications at the end of the teacher education period (second measurement). The presumptions by Nanjundeswaran et al22 that the VHI would reduce in the trained group and increase in the control group can therefore not be supported by our data. Even more, Timmermans et al12 found that both the trained and the untrained groups significantly reduced the VHI values without interaction effect instead of increasing it. Interestingly, the VHI values contrast with the findings of the voice quality as measured by the DSI where the trained group clearly improved their voice quality. Therefore, the training program seems to have less impact on the impression of having a vocal handicap that arose with teaching and speaking experiences. Nevertheless, the mean values of both groups were still below the threshold indicating a mild voice handicap (<7) according to Nawka et al.24 The VLT was used to investigate the voice-carrying capacity. The participants in both groups managed the
requirements of the VLT in the second measurement better than in the first. They read louder and reduced the percentage of SPL <80 dB remarkably. They also increased the F0 during the VLT. These results lead to the assumption that the student teachers of both groups experienced some sort of vocal training probably through the teaching experiences that improved the use and the behavior during the VLT. Nevertheless, the DSI differences between the pre-VLT and the post-VLT showed a significant interaction effect. The trained group was able to keep the vocal quality over the VLT in the second measurement. Hence, the voice training had a clear effect on the voice-carrying capacity to stand certain vocal demands. In more detail, the most influencing factor seemed to be again the lowest vocal intensity. The trained group was able to perform phonations with recognizable lower intensity than the control group after the VLT. The results of this study have therefore shown that the prevention training program on vocal and mental health positively affected vocal functioning. To indicate the importance of the components in the training program, future researches should investigate effects of specific implements according to the profession and the comparison with other training programs.
TABLE 7. Mean Values of the Acoustic Parameters as a Difference Between Before and After the Vocal Loading Test (VLT) at Both Measurement Times Intervention Group (n ¼ 123) Measurement F0 Diff. females (Hz) F0 Diff. males (Hz) Low. Int. Diff. (dB) Jitter Diff. (%) MPT Diff. (s) DSI Diff.
Control Group (n ¼ 81)
First
Second
First
Second
2.9 (108) 41.6 (92) 2.12 (3.3) 0.06 (0.2) 0.29 (3.1) 0.56 (1.0)
5.3 (100) 2.3 (103) 1.39 (2.9) 0.01 (0.3) 1.1 (4.1) 0.22 (1.0)
15.3 (119) 11.8 (109) 1.99 (3.1) 0.02 (0.2) 0.68 (3.4) 0.50 (.87)
16.8 (128) 3.5 (103) 2.56 (3.4) 0.01 (0.3) 0.37 (3.9) 0.60 (1.0)
Abbreviations: F0, fundamental frequency; MPT, maximum phonation time; DSI, Dysphonia Severity Index. Note: Standard deviation values are given in brackets.
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TABLE 8. Statistical Analysis of the Voice Parameter Differences Before and After the Vocal Loading Test (Table 7) on Time, Group, and Interaction Effects Measurement F0 Diff. females (Hz) F0 Diff. males (Hz) Low. Int. Diff. (dB) Jitter Diff. (%) MPT Diff. (s) DSI Diff.
Time Effect (First/Second Measurement)
Group Effect (IG/CG)
Time 3 Group Interaction Effect
F(1,154) ¼ 0.027; P ¼ 0.871 F(1,46) ¼ 0.649; P ¼ 0.425 F(1,202) ¼ 0.063; P ¼ 0.802 F(1,202) ¼ 2.734; P ¼ 0.100 F(1,202) ¼ 7.237; P ¼ 0.008 F(1,202) ¼ 1.613; P ¼ 0.206
F(1,154) ¼ 0.760; P ¼ 0.385 F(1,46) ¼ 1.573; P ¼ 0.216 F(1,202) ¼ 2.423; P ¼ 0.121 F(1,202) ¼ 0.196; P ¼ 0.658 F(1,202) ¼ 4.164; P ¼ 0.043 F(1,202) ¼ 2.172; P ¼ 0.142
F(1,154) ¼ 0.001; P ¼ 0.973 F(1,46) ¼ 1.542; P ¼ 0.221 F(1,202) ¼ 4.364; P ¼ 0.038 F(1,202) ¼ 0.972; P ¼ 0.325 F(1,202) ¼ 0.185; P ¼ 0.668 F(1,202) ¼ 5.057; P ¼ 0.026
Abbreviations: F0, fundamental frequency; MPT, maximum phonation time; DSI, Dysphonia Severity Index. Note: Interaction effects (in bold: P < 0.05).
CONCLUSIONS In this study, the effectiveness of a prevention training program on vocal health of German student teachers was investigated. The results indicate that the teacher education period for student teachers was experienced as a voice-demanding time and that the participants developed certain voice strategies through teaching practices. The trained group, however, increased not only their voice quality over time but was also able to withstand vocal loading and kept their vocal quality with statistical significance. These results showed the potential of a prevention program for student teachers on their vocal health. The findings should lead to consequences to better inform and train teachers and especially future teachers how to manage with certain work-related voice demands and to provide prevention programs for voice training. It is important to learn more about one’s own voice and to understand its limitations and vocal capacity. Furthermore, voice problems should be taken more seriously, and on repeated appearance, speech experts should be consulted.
FIGURE 4. Dysphonia Severity Index (DSI) differences between pre-VLT and post-VLT at both measurements for both groups (Error bars present the standard error of the mean, *P < 0.05).
Acknowledgments The authors would like to thank Nisma Bux-Cherrat, Juliane Stein-Vogel, Dr. Louisa Traser, and Dr. Sebastian Dippold for providing the measuring procedure and the examinations. Further special thanks go to the heads of the teacher education seminars Prof. M. Frommhold, Ms. M. Neumann, Ms. N. Kr€ankel-Schwarz, and Mr. T. Sachsenheimer for the support in recruiting the student teachers. The study was funded by the Ministry of Science and Arts and the Ministry of Culture, Youth, and Sports in Baden-W€urttemberg. The authors declare no conflict of interest.
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