Study of noise pollution in urban and the suburbs railway company of Tehran in 2010
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Background and aims: Noise pollution is one of the risk factors of the human environment that may seriously threat physical and mental health of human beings. One of the main sources of this type of pollution is the noise produced by urban transportation and traffic, particularly subway in the environment. This article aims at study and evaluation of the noise condition in drivers' cabin and inside wagons of the subway of Tehran and the suburbs. Methods: Noise level and noise frequency analysis in the trains of lines one, two, four and five of the subway which are among the active lines of Tehran subway and the suburbs have been measured and evaluated at 345 points within one week over two days while the train was moving and stopped of which 96 points were located inside the driver's cabin and 258 points were in wagons. Noise was evaluated based on Free Air Standard approved by the Environment Higher Council of Iran and ACGIH Organization. The subway trains were also compared regarding noise pollution based on type of the train (TM, DC, AC). Calibrated analyzer instrument, model CEL-450/490 was used to measure noise and the data were analyzed by statistical descriptive methods, t-test and analysis of variance by SPSS18 software. Results: Mean equivalent noise level measured in the moving wagon was equal to 71.9 dBA that is significantly higher than the standard level (65 dBA) (p < 0.01). In case the mean equivalent noise level measured in the moving cabin is equal to 73.3 dBA, that is significantly less than the standard level (85 dBA) (p < 0.01). There is a significant difference between mean noise pressure level in wagon and in driver's cabin while moving and stoppage (p < 0.01). However, there is no significant difference between noise pressure level in the wagon and driver's cabin while moving (p=0.5). There is no significant difference between the mean noise pressure level while moving and stoppage in different frequencies inside the wagon (p=0.5). However, there is a significant difference between the mean noise pressure level while moving and stoppage in 250 and 500 frequencies in the cabin (p < 0.01). TM1 and TM2 trains are in the same class considering mean noise equal level and noise pressure (p=0.667) and AC and DC trains are in the same class (p=0.5) and their mean noise is equal to 69.5 and 73, respectively. Conclusion: The results obtained in this research showed that the mean equivalent noise level in the cabins is less than the authorized limit; however, it is higher than the authorized limit in the wagon. Therefore, it seems necessary to take control and prevention measures for noise reduction inside wagons.