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|Year : 2013
: 15 | Issue : 67 | Page
|Classroom acoustics and hearing ability as determinants for perceived social climate and intentions to stay at work
Roger Persson1, Jesper Kristiansen2, S°ren P Lund2, Hitomi Shibuya2, Per M°berg Nielsen3
1 National Research Centre for the Working Environment, Lers° ParkallÚ 105, DK-2100 Copenhagen, Denmark; Department of Psychology, Lund University, Lund, Sweden
2 National Research Centre for the Working Environment, Lers° ParkallÚ 105, DK-2100 Copenhagen, Denmark
3 Akustik Aps, Trekronergade 15, 1, 2500 Valby, Denmark
Click here for correspondence address
|Date of Web Publication||12-Nov-2013|
Background noise and room acoustics may impede social interactions by interfering with oral communication and other cognitive processes. Accordingly, recent research in school environments has showed that social relationships with peers and teachers are described more negatively in rooms with long reverberation times (RT). The purpose of this study was to investigate how RT and hearing ability (i.e., hearing thresholds [HT] and distortion product oto-acoustic emissions) were associated with schoolteachers' perceptions of the social climate at work and their intentions to stay on the job. Schoolteachers (n = 107) from 10 schools that worked in classrooms classified by acoustical experts as "short RT" (3 schools, mean RT 0.41-0.47 s), "medium RT" (3 schools, mean RT 0.50-0.53 s), and "long RT" (4 schools, mean RT 0.59-0.73 s) were examined. Teachers who worked in classrooms with long RT perceived their social climate to be more competitive, conflict laden, and less relaxed and comfortable. They were more doubtful about staying on the job. Even if the teachers were generally satisfied with their work the results suggest that the comfort at work may have been further improved by acoustical interventions that focus on reducing sound reflections in the classrooms. Yet, due the study design and the novelty of the findings the potential practical significance of our observations remains to be evaluated.
Keywords: Education, noise, reverberation, school, teacher, well-being
|How to cite this article:|
Persson R, Kristiansen J, Lund SP, Shibuya H, Nielsen PM. Classroom acoustics and hearing ability as determinants for perceived social climate and intentions to stay at work. Noise Health 2013;15:446-53
|How to cite this URL:|
Persson R, Kristiansen J, Lund SP, Shibuya H, Nielsen PM. Classroom acoustics and hearing ability as determinants for perceived social climate and intentions to stay at work. Noise Health [serial online] 2013 [cited 2019 Jun 18];15:446-53. Available from: http://www.noiseandhealth.org/text.asp?2013/15/67/446/121254
| Introduction|| |
Teaching involves the use of cognitive and communicative skills. Despite the introduction of new technologies, oral communication is still the predominant method for disseminating knowledge. However, both cognitions and oral communication are known to be sensitive to interference from background noise and the quality of room acoustics. , For example, reverberating rooms and high background noise have been shown to reduce the intelligibility of speech and interfere with the phonological processing of speech, thus impairing memory consolidation of the information. ,,, In addition, classrooms with very long reverberation times (RT) (1.0 s or more) have been reported to be associated with less positive student evaluations of social relationships with peers and teachers.  Likewise it was recently observed that noise in classrooms with RT in the range between 0.7 and 0.9 s impeded students' conversational interactions and collaborative learning.  While this latter study is descriptive and makes no statistical inferences it suggest the possibility that social effects may be present at commonly occurring RT levels that by no means are extreme.
Even if contemporary building regulations advocate that RT should not exceed 0.6 s , the regulations have been gradually implemented over time. Accordingly, many buildings in society, including schools buildings, are often far older than the regulations and have yet to be renovated to meet the standards. But even in situations when classrooms have been built, or renovated, to meet the standards, we have in some instances observed that incorrect mounting of ceilings or wrong maintenance (for example, painting over acoustical ceilings or wall absorbents) has reduced the effectiveness of the sound absorbing surfaces. For example, measurements that we have carried out in 63 standard classrooms in 14 schools showed that RT exceeded 0.6 s in 43% of the rooms (unpublished data). Likewise, Seidel et al. reported that the RT exceed the German standard in many classrooms.  Hence, although current standards prescribe a maximum RT of 0.6 s in rooms used for teaching purposes, measurements show that this is exceeded in many cases. Considering that 64% of the schoolteachers that responded to the Danish work environment cohort study in 2010 reported that they were exposed to disturbing noise in at least one-quarter of their working hours, the question arises as to what degree acoustics and disturbance are associated with work performance and social relationships at work. However, only a few studies seem to have addressed these questions and those that have has primarily focused on the consequences for the students. ,,,
In any event, since teachers and pupils to a large extent share environments, it appears plausible that the acoustic environment and high noise levels via increased cognitive load and general feelings of discomfort also may exert a negative influence on teachers' social relationships and well-being. From this perspective, and since humans often deal with stressful situations by affiliating with other human beings in search of positive social contacts or support,  it seem especially interesting to pursue the potential effects noise and acoustics have on social relationships. However, it seem also important to recognize that people's hearing ability may vary and that poor hearing may make social exchanges more effortful.  Against this background we decided to investigate how classroom RT and hearing ability were associated with schoolteachers' perceptions of the social climate at work. The investigation included assessment of hearing thresholds (HT), distortion product oto-acoustic emissions (DPOAE), and questions about the social climate at work and intentions to stay on the job. It was hypothesized that working in long classroom RT's and a relatively lower hearing ability would be associated with more negative evaluations of the social climate at work and lesser intentions to stay on the job.
| Methods|| |
In total 107 schoolteachers from 10 schools participated in the study. As there were 419 potential participants, circa 25% of the teacher population were examined. Of the 107 teachers, there were 30 men and 77 women. The mean age for the men was 43 years (standard deviation [SD] = 10 years) and the mean age for women was 44 years (SD = 10 years). On average, the men had 15 years of work experience (SD = 11 years) and the women had 14 years of work experience (SD = 11 years). The teachers were identified from 10 schools in the municipality of Copenhagen. None of the teachers used hearing aids and only three teachers had a hearing handicap ranging between 0.6 and 8.6% as calculated according to recommendations by the American Academy of Otolaryngology-Committee on Hearing and Equilibrium and The American Council of Otolaryngological-Committee on the Medical Aspects of Noise (1979).
Identification and acoustical classification of schools
In brief, 25 of 55 schools in the municipality of Copenhagen were inspected and screened for classroom RT. To secure that the study could be performed and improve the chances for high participation, inclusion criteria were (a) absence of current renovation plans of regular classrooms, and (b) a high response rate (at least 50%) in a recent work environment survey conducted by the municipality of Copenhagen. In any event, in each school regular classrooms were inspected and the acoustical quality of the room was assessed by two acousticians. Within each school, the two acousticians also assessed the similarity of classrooms with respect to acoustics including the shape and volume of the room. The RT was defined as the time it takes for a sound level to drop 60 dB after the sound emission has stopped. RT was assessed as T30, which is the time for a sound impulse to decay 30 dB and then extrapolating this to a 60 dB decrease. The measurements were conducted in accordance with the principles as described in ISO 3382-2  under the integrated impulse response method. The impulse was generated by the sudden release of pressurized air, and the response was measured by a Brüel and Kjær 2260 sound level meter and further analyzed in octave bands from 125 to 4000 Hz using a Brüel and Kjær 7830 Qualifier. The measurements were based on two different sound source positions at three different microphone positions in classrooms without pupils, and the RT was expressed as the average RT in the octave bands from 125 Hz to 4000 Hz.
Grouping of classrooms according to their RT
The RT was used as the primary determinant. The 25 schools received an overall classification according to their classroom RT, either "short RT," "medium RT," or "long RT." To ensure that the teachers in each school to the greatest possible extent shared a similar acoustical environment ten schools that were judged to be acoustically "homogeneous" across classrooms were invited to participate in the study. All schools accepted the invitation and three schools were classified as "short RT" (mean RT = 0.44 s, range 0.41-0.47), three schools as "medium RT" (mean RT = 0.51 s, range 0.50-0.53), and four schools as "long RT" (mean RT = 0.65 s, range 0.59-0.73). The teachers were not informed about the acoustic classifications of the schools during the study and were in effect blinded to this study parameter. In addition, the acoustical experts had no knowledge about which teachers worked in which classrooms.
Perceived social climate at work
Five items from the General Nordic Questionnaire for Psychological and Social Factors at Work (QPS-Nordic) were used to assess various aspects of the social climate at work.  The items were preceded by a general statement: "how would you describe the social climate at your workplace…" and were followed by five descriptive items, "competitive," "encouraging and supportive," "distrustful and suspicious," "relaxed and comfortable," and "rigid and rule based." These five items were supplemented with one additional item, "conflict laden." All items were ranked by respondents on a 5-point scale: Not at all = 1, to a small degree = 2, partly = 3, to a high degree = 4, and to a very high degree = 5.
Intention to stay at work
One item was constructed to assess to what extent the teachers intended to continue at their current workplace. The question read: "Do you wish to stay at your workplace during the next 3 years?" The question was responded to on a 5-point scale: Not at all = 1, to a small degree = 2, to some degree = 3, to a high degree = 4, and to a very high degree = 5.
Otoscopic examinations were performed before the hearing tests, and individuals with excessive ear wax were asked to contact their doctor to remove the ear wax before the hearing test. All hearing tests were performed in a transportable sound booth (Industrial Acoustics Company 250 Sound Shelter, complying with ISO 6189). DPOAE were performed binaurally with two identical digital signal processing systems from Tucker-Davis Technologies (TDT, Alchua, FL) and two Etymotic Research (ER, Elk Grove Village, IL) microphone probe systems (ER10B+ connected by tubes to ER2 sound transducers). Before measurements of either HT or oto-acoustic emissions, proper earplug fittings were tested by measuring the output from each transducer in situ at 500 Hz. The DPOAE assessments of each ear consisted of two DP-grams with measurements of the cubic distortion product (CDP = 2 f1-f2) from 33 sets of primary input tones (f2/f2 = 1.23; f2 ranging from 707 Hz to 10,374 Hz). The frequencies were grouped in three frequency bands: Low (f2 less than 2 kHz), mid (f2 between 2 and 4 kHz), and very high (f2 above 4 kHz). For all frequency bands, the results from the best ear were used as an indicator of hearing.
The same setup and probe systems were used for assessments of pure-tone HT (HT: 125 Hz, 250 Hz, 501 Hz, 1001 Hz, 1541 Hz, 2000 Hz, 3085 Hz, 3999 Hz, 6169 Hz, and 7999 Hz) by an experienced technician in 5 dB steps. The HT were determined twice at each frequency from sub-thresholds, starting at 1001 Hz and upwards in frequency, then returning to 1001 Hz and downwards in frequency. The testing was started alternately with right or left ear, and each participant was tested only once.
Both the HT and DPOAE assessment were expressed as continuous scores.
Information was also collected on a number of background variables that were potential confounders including gender, age, seniority as a teacher, seniority in the present job, work hours, perceived noise disturbance during teaching, perceived annoyance from noise outside classroom, perceived annoyance from noise inside classroom, number of children in the class, and distribution of students in relation to their current grade at the time of investigation. The distributions of these variables across acoustical conditions are presented in [Table 1].
|Table 1: Crude distributions of various demographic characteristics across schools with varying RT|
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Statistical computations were made with IBM SPSS version 20 (IBM Corporation, Software Group, Somer, NY, USA). Two-sided P ≤ 0.05 were considered statistically significant. Background data were presented as percentages or as mean scores with accompanying SDs. Pearson's Chi-square test, ordinary Z-tests, and independent Kruskal-Wallis tests were used to evaluate whether the background variables were statistically significantly unequally distributed across the RT group's [Table 1]. Spearman's rho correlations explored relationships between the gender, age, hearing ability (DPOAE and HT), social climate and intention to stay on the job scores.
Unadjusted univariate analysis of variance (ANOVA) analyses examined the crude differences in mean levels between the three different RT conditions. Since there was a tendency for unequal distribution of men and women and the age distribution across the three RT conditions, we also performed age, gender and hearing adjusted univariate ANOVA analyses. To avoid over adjusting the statistical model, and because age and seniority was very highly correlated (rho = 0.86), we only adjusted for age. In any event, and to test whether hearing ability (i.e., DPOAE and HT) moderated the effect of the RT condition the first round of statistical analyses incorporated the two-way interaction between hearing ability and RT. Since there were two different types of hearing ability scores and HT expressed for three frequency bands (low (f2 less than 2 kHz), mid (f2 between 2 and 4 kHz), and very high (f2 above 4 kHz)), six different interaction models were calculated for each outcome. Since there typically was no interaction between any of the hearing measures and RT, the results were calculated as main effects models. The results from the adjusted models are expressed as difference scores with accompanying 95% confidence intervals. Due to occasional internal missing data the number of persons included in the various statistical analyses may slightly vary.
| Results|| |
There was typically no statistically significant interaction between DPOAE, HT, and the RT on the ratings of the social climate and intentions to stay on the job. Only for the very high frequency band there was one statistically significant interaction between RT and HT on the distrustful and suspicious score (Interaction: F (2, 88) = 3.40, P = 0.038, ηp = 0.07). Post hoc analysis revealed that teachers who taught in classrooms with short RT and who had poorer hearing in the very high frequency reported the social climate to be more distrustful and suspicious. However, since there was no clear pattern of statistically significant interaction effects, the statistical model was simplified and the results were calculated as main effects models.
[Table 2] presents the correlations between the gender, age, hearing ability, social climate and intention to stay on the job scores. The inter-correlations for social climate scores ranged between rho = −0.40 and rho = 0.49. Five of the six social climate scores correlated statistically significantly with the intention to stay on the job score (rho's between −0.25 and 0.48). The correlations between hearing ability scores on one hand and on the other hand, social climate and intention to stay on the job scores were not statistically significant (rho's between −0.18 and 0.17).
The unadjusted univariate ANOVA showed that teachers who worked in classrooms with long reverberations were less positive about the social climate at work than teachers who worked in classrooms with short or medium RT [Table 3]. Specifically, the teachers who worked in classrooms with long RT reported that they perceived their social climate to be more competitive (F (2, 101) = 6.23, P = 0.003, ηp = 0.11), more rigid and rule based (F (2, 101) = 3.47, P = 0.035, ηp =0.06), and conflict laden (F (2, 101) = 7.59, P = 0.001, ηp = 0.13), and less relaxing and comfortable (F (2, 104) = 7.04, P = 0.001, ηp = 0.12).
The age, gender, and hearing-adjusted univariate analyses essentially confirmed this pattern of results [Table 4]. Irrespective of frequency band and hearing assessment (i.e., DPOAE and HT) there were only minor alterations in the F-values and the estimated effect sizes. Likewise, conducting the analyses without adjusting for age did only create minor alterations in the F-values and effect sizes (data not shown). The results in [Table 4] present the data when adjusted for age, gender and HT in the low frequency band.
|Table 4: Mean differences for teachers grouped according to RT when adjusted for age, gender, and hearing thresholds in the low frequency band (f2 less than 2 kHz)|
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Intentions to stay on the job
The unadjusted univariate ANOVA showed that teachers who worked in classrooms with long reverberations were less positive about their intentions to stay on the job than teachers who worked in classrooms with short or medium RT (F (2, 104) = 8.43, P < 0.001, ηp = 0.14) [Table 3].
The age, gender, and hearing-adjusted analyses confirmed the statistical association between RT and the intention to stay score [Table 4]. Irrespective of frequency and hearing assessment (i.e., DPOAE and HT), there were only very minor alterations in the F-values and the estimated effect sizes.
| Discussion|| |
In the present study, we examined whether classroom RT were associated with schoolteachers' reports of the social climate at work and their intentions to stay on the job during the next 3 years. Even if the schoolteachers described their social climate positively, we observed that schoolteachers who worked in the classrooms with the longest RT's described the social climate less positively than teachers who worked in the classrooms with the shortest RT's. As verified by assessments of HT and DPOAE, we observed that the absolute majority of the teachers had relatively good hearing in relation to their age. Accordingly, this invalidates the test of our original hypothesis and our data does therefore not permit any conclusions as regards how acoustical conditions may negatively affect teachers with poor hearing. On the other hand, there is no way of a priori knowing whether a teacher has a good hearing without conducting a hearing test. In view of the teacher's good hearing capabilities, it appears in hindsight not surprising that neither HT nor DPOAE independently, or in interaction with RT, correlated with reports of the social climate at work or intentions to stay on the job. In the absence of a pattern of interactions, one interaction that actually reached statistical significance is difficult to understand and may well be a coincidental event. In any event, it seems unlikely that normal variations in teachers' hearing substantially contribute to the perception of the social climate or reports of intentions to stay on the job. To what extent the good hearing ability reflects a healthy worker effect is not known.
More than 80% of the teachers reported that they were exposed to noise that disturbed them during work for at least one-quarter of the working time. The most disturbing noise sources were student behaviors and noise from the corridor and adjacent classrooms. A lesser degree of disturbance was reported in relation to ambient noise (i.e., noise from road, train or aircrafts) or the technical equipment and ventilation in the classrooms. Even if the group of teachers that worked in schools with moderate RT's reported being less disturbed by ambient noise than teachers who worked in classrooms with short or long RT's, the average disturbance level was often low to moderate and fairly similar across the three different RT conditions.
Because the teachers reported the students to be the main source of disturbing noise it seem plausible that interventions aimed at social behaviors may decrease noise levels in classrooms and adjacent areas (e.g., corridors). However, changing student behaviors may be a long-term project. Even if early interventions at school start seem to have positive and long lasting effects older students appear less receptive for pedagogical interventions.  Interestingly, other studies indicate that improving the room acoustic alone may reduce sound levels and make students behavior calmer.  Hence, combining acoustical and pedagogical interventions seem pertinent. Indeed, as pointed out by Rawool the most effective approach to hearing conservation is direct noise control.  Regarding noise from students, direct noise control could entail rules for verbal communication and student behavior as well as implementing technical solutions (e.g., using quiet materials and equipment).
All in all, our results agree fairly well with previous findings that noise in classrooms with RT in the range between 0.7 and 0.9 s obstructed students' conversational interactions and collaborative learning.  The results also correspond to the observation that long RT (1.0 s or more) has been found to be associated with less positive student evaluations of social relationships with peers and teachers.  It should, however, be noted that our long RT were in the range of 0.6-0.7 s and were thus somewhat lower than in previous studies. While this circumstance may lead to a relative underestimation of the effects it underlines that small a variation in RT in fairly normal acoustical conditions may have an impact.
Since our RT conditions agree fairly well with the new Danish building regulations from 2008 that recommend that the RT should be no longer than 0.6 s , our RT classification appear realistic and externally valid. Considering that the recommendation prior to 2008 stated that RT should be no longer than 0.9 s and that the absolute majority of schools have been built well prior to 2008 suggest that acoustics is still a problem that should receive proper attention in future renovation plans. That the RT many time exceed recommendations is further underlined by a German study  and our own measurements in 63 standard classrooms in 14 schools, which showed that RT exceeded 0.6 s in 43% of the rooms (unpublished data).
In view of the fact that teachers who work in classrooms with short RT perceive their social climate in more positive terms than teachers who work in classrooms with long RT, our results suggest that it might be gainful to build classrooms with even shorter RT. The findings also underscore that classroom acoustics may have wider social consequences. Therefore, our results extend beyond the known and immediate problems associated with deprived acoustical conditions, for example, annoyance reactions, communicative interference, reduction of speech intelligibility, and memory consolidation of information. ,, Importantly, however, it should be noted that our study was not designed to disclose to what extent the effect of RT on the social climate and intention to stay on the job was mediated by immediate phenomena such as annoyance reactions, communicative interference, speech intelligibility, memory consolidation or actual sound levels in the classroom. Yet, it seems plausible that one, or many, of these known acoustically dependent phenomena in various ways may serve to affect feelings of comfort and social relations and therefore in extension influence the perception of the social climate and ones intentions to stay on the job.
Before reaching to the conclusions, some additional methodological issues need to be addressed. Indeed, there are both strengths and limitations of our study. One limitation is the size of our study. While the inclusion of 10 schools improves the external validity the relatively small study sample consisting of 107 teachers obviously constrain the statistical power and the possibilities of finding small effects. A second limitation is the predominance of women teachers. This predominance suggests that extrapolation of the results should be done with careful consideration. A third limitation is the cross-sectional design, which obviously limits the confidence in mechanistic conclusions. However, given that both hearing ability and RT reflect lasting physical properties of the ear/brain function and the classroom, respectively, it seems reasonable to view them as determinants. This is perhaps especially the case since the determinants were measured independently of the effects and that it is difficult to see how a person's hearing ability and classroom RT may be affected by the social climate or the intentions to stay on the job. Hence, by focusing on lasting physical parameters and using experts to measure both RT and hearing ability we have limited the risk for reverse causation and common method bias.  Even so, a limited risk is not equal to fact, and the possibilities for rejecting alternative explanations had been greater in an experimental design that entails changing the acoustical conditions in the classroom. However, that type of design was not feasible at the time of our investigation. Instead, we selected a strategic sampling of classrooms in a cross-sectional design. It may also be noted that RT was assessed as a physical property of an empty classroom. Since students in effect are sound absorbers it is likely that the RT's measurements had been different if assessed when populated. From this perspective, however, it is somewhat reassuring that the social circumstances in terms of the number of students in each classroom, the grade of the students, the seniority of the teachers, the teacher's weekly work hours, and the teacher's perceived disturbance from noise exposure were fairly equal across the three RT conditions. Accordingly, it is not likely that these factors have biased the results. Based on this information it seems also reasonable to conclude that any variation in the teacher's pedagogical skills and methods (which are known to be heterogeneous within and between schools in Denmark due to a dictum on pedagogical freedom) have had a similar impact on their experience of noise. Hence, any existing variations in teaching style and classroom management are not reflected in the perception of noise across the three RT conditions. Undeniably, however, the subjective experience of noise disturbance does not need to reflect actual sound levels.
Another concern is the fact that the teachers were drawn from 10 different schools which may differ in many ways. However, since all ten participating schools were from the same municipality, it seems improbable that discontent due to poorer economic conditions and variations in resource allocations among schools explain the variations in reports of the social climate. In addition, as verified by the acoustical experts who visited each school when conducting the RT measurement, despite different construction styles, the general physical appearances of the schools were fairly similar. However, there were slight variations between schools. Our subjective impression from visiting the schools is that some of the extant variation in RT's could be due to refurbishment of the ceilings, the use of different materials in the ceiling and interiors (e.g., notice boards, cabinets, furniture, etc.,), and in some instances inappropriate maintenance of the ceilings (for example, painting of acoustic ceilings, etc.,).
A final issue that needs to be commented is the fairly large effect sizes. The effect sizes are perhaps especially interesting in view of the relatively narrow range of observed classroom RT's (0.41-0.73 s). Even if we have divided classrooms as "short" (0.41-0.47 s), "medium" (0.50-0.53 s) and "long" (0.59-0.73 s), it should be noted that it might be difficult for non-acousticians to perceive these differences unless they explicitly are made aware of the acoustical conditions and have access to an immediate comparison (e.g., two rooms with different RT that are adjacent to each other). Indeed, as may be verified by most people's everyday experiences, we seldom focus on the acoustical environment unless it evokes annoyance or gives us pleasure (e.g., music). In any event, it should be emphasized that the issue of the optimal acoustical working conditions for school teachers is complex. In the present study, we have addressed the impact on aspects of the social working climate and the effects of hearing ability. Other endpoints may also be relevant, such as the teachers' vocal efforts which are also affected by the acoustical working conditions.  Finally, one must also realize that the RT is a crude acoustical parameter, and that other parameters such as clarity or the ratio between early and late sound reflections may turn out to be more relevant in characterizing and optimizing school teachers' acoustical working environment. Yet, since the RT often is correlated with other acoustical parameters it represents a feasible choice, as for example, verified by its use in a contemporary building regulations. 
| Conclusion|| |
The teachers described the social climate in positive terms. However, teachers who work in classrooms with long RT perceived their social climate less favorably and reported having weaker intentions to stay on the job as compared with teachers who worked in classrooms with shorter RT. Even if the teachers were generally satisfied with their work, the results suggest that the teachers' comfort at work may be further improved by acoustical interventions that focus on reducing sound reflections. Yet, due to the study design and the novelty of the findings the potential practical significance of our observations remains to be evaluated.
| Acknowledgments|| |
This study was supported by the Danish Working Environment Research Fund, Grant no. 16-2008-03. Our thanks are extended to the participating teachers, the City of Copenhagen, the Teacher Union of Copenhagen, and the Copenhagen School Principal Association for help and collaboration.
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Allhelgona Kyrkogata 14 O, 22100 Lund
Source of Support: This study was supported by The Danish Working
Environment Research Fund, Grant no. 16-2008-03., Conflict of Interest: None
[Table 1], [Table 2], [Table 3], [Table 4]