heexposure of workers to noise is a common problem in working environments across the globe.1 About 10 million workers in the United States suffer hearing loss of more than 25 dB. In the entire world, 16% of hearing loss is due to exposure to noise in work environments.
2,3 An estimate of available data shows that about 2 million workers in Iran are exposed to harmful noise.
4Exposure to noise can cause hearing loss in addition to a lot of other problems, including lack of concentration, loss of professional ability, distress and stress, and low productivity in workers.
5 Sound disturbance, as a measurable mental response, is one of the most important adverse effects of sound.
6 According to WHO (World Health Organization) findings, noise-induced distress has harmful and unpleasant effects on health-related quality of life.
7 In a research, the study of 4 occupations exposure in construction workshops was carried out. The results of the regression analysis showed that the type and characteristics of the work were related to increase in sound exposure levels.
8 In a study on the effect of noise and shift work on worker fatigue as a function of age, it was shown that exposure to noise has a major impact on fatigue and as the duration of exposure increases, the level of weariness of workers also increases.
9
The results of the correlation test in the study of the relationship between exposure to noise pollution caused by traffic and the quality and quantity of sleep among police officers of the city of Tehran showed significant correlations between the hours and the frequency of night sleep awakening, and the variables of age, noise and the sensitivity to traffic noise.
10 A study at the Bangkok power plant showed that although the sound was lower than the standard limit, noise annoyance was significant and based
on evaluations, it was found that noise was higher than 55 dB over the environment, which can
cause various health problems.
11According to the mentioned studies, it can be concluded that there has been no research on the level of exposure and disturbance caused by noise in construction workshops.
Therefore, the present study aimed to investigate the association of noise disturbance among workers at the construction workshop.
Methods
This research was carried out in the spring and summer of 1395 at several construction workshops with the dominant construction activity in the city of Tehran during the construction of wall. In these construction workshops, different sources of sound including electricity generator, machines and hand tools were used. The population surveyed in this study was made up of all construction workers working in these workshops. All participants were male, and the protocol was reviewed and approved by the ethics committee of Tehran University of Medical Sciences and approved by number ***. Informed consent was obtained from all participants in this study. Entry criteria included working for at least 5 days a week at the construction workshop and not having hearing impairments. Also, people who did not complete the informed consent were excluded from the study. According to previous studies, 70 people were required to reach 80% power at the significant level of 5%. Considering the decrease of 20% and in order to compensate for the possible impact of this fall, a total number of 96 individuals from the workshops were randomly assigned.
In order to investigate the relationship between noise disturbance and exposure to noise in different occupational groups, the subjects were classified into four executive, administrative, supervisory and machinery groups. , A questionnaire and a sound meter were used to assess the exposure and outcome in this study. To determine the sound disturbance, the
Sound Disturbance Questionnaire" Acoustic- sound disturbance assessment using social audit and socio-acoustic" was used. Validity of the Persian translation of this questionnaire was reviewed by Ali Mohammadi with specification of ISO/TS 15666. In order to determine the occupational exposure level of individuals, dosimetry in network A according to ISO 9612: 2009 standard was used for each individual. It was standardized to determine the exposure levels of occupational groups. The dosimeter used in this design is the CEL-272 model, which complies with the IEC 29, TC 29 / WG 4, IEC Draft Document ISO 1999.
The collected results were first studied for descriptive statistics including mean, range and standard deviation of observations. Compliance with normal distribution in data was studied to select either parametric or nonparametric tests. Non-parametric tests were used in case of violation of normal distribution. The difference in reported mean of audio disturbance in the occupational groups was assessed by one-way analysis of variance. The correlation between the exposure values and the reported disturbance score were analyzed by Pearson and Spearman correlation tests. Comparison of mean in abnormal cases was done by Kruskal-Wallis test. The significance level was considered in all tests as 5%. All analyzes in this study were performed using SPSS21 software.
Results
In this study, the workers were classified into four groups: executive, administrative, supervisory and machinery groups. The 8-h equivalent sound level was calculated according to the formula of the measured dosimetry results for each person. First, Kolmogorov Smirnov and Shapiro Wilk tests were used to determine the normality of the data. The results showed that the data follows the normal distribution. Table 1 shows the descriptive statistics (average, standard deviation, mean, median, minimum and maximum) of audio exposure data divided by occupational groups. As shown in this table, the average noise exposure of the executive job group was 82.28, office group was 66.52, supervisory was 76.43, and machinerywas78.45, which indicates an increase in the average noise exposure of the executive job group. According to the results of ANOVA and Kruskal-Wallis test, there was a significant difference in noise exposure among occupational groups. Differences in noise exposure of executive, administrative, supervisory and machinery groups were significant, and the executive job group with the mean of 82.28 had the highest average exposure. Moreover, the administrative group had the lowest noise exposure level of 66.59 dB A. Scheffe test did not show any significant difference between the noise exposure of the supervisory group and the machinery group at the level of 0.05. Only executive group with administrative group and executive and supervisory groups had significant
difference in the amount of exposure to noise.
The mean of sound disturbance in the executive, administrative, machinery and supervisory groups is 6.9, 4.7, 5.0, and 5.2, respectively.
The average noise exposure and disturbance in the executive job group was higher than the other occupational groups, and lowest amount of exposure to noise and sound discomfort was observed in the administrative occupation group. In order to study the normality of the variables of sound disturbance in occupational groups, age and work experience, Kolmogorov Smirnov and Shapiro-Wilk tests were used. The results indicated that sound disturbance in the executive and supervisory groups followed non-normal distributions and in the administrative and machinery groups followed normal distribution. Therefore, both parametric and non-parametric tests were performed. ANOVA and Kruskal Wallis tests of sound disturbance showed a significant sound disturbance among the occupational groups. The Scheffe and Pairwise tests showed a significant difference in sound disturbance between the executive and administrative groups, machinery and supervisory groups at a 5% error rate. However, no significant difference was found between the other groups.
The results of Pearson and Spearman correlations of noise exposure and disturbance showed high correlation. The value of R2determination coefficient in linear regression between 8-h noise exposure and disturbance indicates that noise exposure variable can justify 40.7% of the variations of the response variable, that is, sound disturbance. It can also be stated that at a 5% error level, with a change of 1 dB in 8-h noise exposure, 0.19 units was added to an individual's sound distraction score.