Journal of Health and Safety at Work

---

Introduction: Traffic noise has been thought as a major environmental stress in modern societies, and the cause of physiological and psychological disorders according to the World Health Organization. Moreover, traffic noise can interfere with mental performance. However, there is little coherent evidence showing the effect of traffic noise on individuals’ performance. Hence, this paper aimed to address the role of traffic noise in participants’ mental performance considering the complexity of the activity.
 

Material and methods: Thirty-five master students studying in Tehran University of Medical Science were recruited for this study. Traffic noise was recorded by tape recorder and the traffic noise level was simultaneously measured by sound meter. Then, participants had been separately sitting in silent compared to traffic noise environment before they performed the tests including “S₃”-type Choice Reaction Time (CRT) test as a simple activity and “S1”-type Determine Test (DT) as a complex activity taken from “Vienna Test System” software package.
 

Results: The comparison between scores resulted from DT and CRT tests ,before and after exposure to traffic noise under simple activity conditions, showed that there was little increase in mean score of reaction time (P-value=0.47) and motor time (P-value=0.49), showing no statistically significant changes in these variables. On the contrary, following exposure to traffic noise, the DT test under complex activity condition revealed that there is a clear decreasing trend in median reaction time(P=0.001), number of stimuli (P=0.014) and number of reactions (p=0.009) in participants, and also, no significant differences were found in correct responses (P=0.091) and incorrect responses (P=0.073).
 

Conclusion: One of the most significant findings emerged from this study is that traffic noise seems to have no effect on the mentioned variables under simple activity condition. However, traffic noise has devastating effects on median reaction time, number of appeared stimuli and reactions under complex activity condition.

---

Introduction: Noise pollution in urban areas has been recognized as a major problem. Since hearing damages are the main concern of noise exposure, other physical and psychological effects should not be ignored. Noise-induced annoyance and consequently its side-effects, such as fatigue and loss of concentration, would increase the probability of human errors occurrence and occasionally irreversible occupational accidents. This matter show the importance of noise exposure level from the standpoint of both community health and workplace safety.

Material and Method: This cross-sectional study was conducted to investigate the annoyance caused by air transportation noise in tehran, 2014. In this sense, a sample of 200 individuals were selected from residential and nonindustrial noise-exposed population in four southwest regions in Tehran. Following, the study questionnaires including annoyance (Recommended based on ISO 15666-2003), visibility of airplane, noise perception, and demographic variables were distributed and completed by the participants. Data obtained from Integrated Noise Model (INM) and geographic coordinates of measurement stations, recorded by Glopal Positioning System (GPS), were entered into the GIS software in order to estimate air traffic noise.

Result: The present study showed that the equivalent sound level of all regions during night, the day average sound level only in the Simetry Jey area, and the average night noise level in all regions except Dorahi Ghopan were more than the acceptable level; and the most precentage of people with high annoyance was belonged to night annoyance rate. On the other hand, the correlation between day level (DL) and day annoyance rate (P=0.01, R=0.142), night level and night annoyance rate (P=0.004, R=0.334), and Day-Night Average Sound Level (DNL) and the day-night annoyance rate (P<0.0001, R=0.235) were obtained statistically significant.

Conclusion: Adopting management srategies for reduction of number of night flights or engineering measures such as improving construction to decrease the rate of receiving noise by exposed people can have a positive considerable effect on declining noise pollution and individuals’ annoyance rate.

---

Introduction: Over recent years, various programs have been conducted to reduce noise, indicating the increasing concerns of society over noise pollution. This study has been performed to enhance the performance of parallel barriers on two sides of a highway considering the surrounding buildings.
Material and Methods: The 2D boundary element simulation method was employed to predict the noise reduction in barriers. Regarding the effect of buildings and water canals, various kinds of models were investigated to compare the effectiveness of different boundary barriers in real conditions from a listener’s perspective.
Results: The use of a single YA model could improve the performance of parallel barriers by 3.5 dB compared to that of a TS model. Moreover, by using a pair of barriers, no significant change was observed in the performance of the second barrier. However, by using parallel barriers along the surrounding buildings, the TD model improved the efficiency by 3 dB compared to the TS model. The rise in the frequency resulted in remarkable adverse effects on the barrier performance, such that the surrounding buildings at a distance of 8 m had a negative effect on the performance of the parallel barriers by almost 8.34 dB.
Conclusion: In general, by ignoring the buildings, the use of a pair of TZ barriers showed a higher performance. Meanwhile, by considering the buildings in the design model, the TD model was found to be optimum. Therefore, it can be concluded that choosing an ideal barrier only based on the noise behind it cannot indicate its behavioral and acoustic characteristics in a real environment.