1- M.Sc. Graduated Student of Environmental Sciences and Engineering, Faculty of Environmental Sciences, Hakim Sabzevari University, Sabzevar, Iran
2- Associate Professor, Department of Environmental Sciences and Engineering, Faculty of Environmental Sciences, Hakim Sabzevari University, Sabzevar, Iran ,ghr_zolfaghari@yahoo.com
3- Associate Professor, Department of Environmental Sciences and Engineering, Faculty of Environmental Sciences, Hakim Sabzevari University, Sabzevar, Iran
2- Associate Professor, Department of Environmental Sciences and Engineering, Faculty of Environmental Sciences, Hakim Sabzevari University, Sabzevar, Iran ,
3- Associate Professor, Department of Environmental Sciences and Engineering, Faculty of Environmental Sciences, Hakim Sabzevari University, Sabzevar, Iran
Abstract: (322 Views)
Most of the noise pollution in big cities is related to traffic, and the construction of highways and traffic flow with high volume and speed creates problems for the nearby residents. Calculating the amount of noise pollution through modeling makes it possible to reduce the effects of noise pollution in the design of highways and surrounding uses. This research, which was conducted on the Hashemi Rafsanjani highway (Misthaq) in Mashhad, by measuring the volume of sound, traffic information, weather information and surrounding uses, using the American federal highway management model (FHWA) with TNM 2.5 software models the emission of noise pollution and compares the obtained results with the measurements made through statistical analysis.
The following steps were implemented for this research: 1- collecting information about the volume and speed of traffic, 2- collecting information and characteristics related to the road such as road width, road type, surrounding land use map, green space around the highway, height and density of buildings around the highway, meteorological information such as temperature and humidity, 4- determining sensitive points around the area in terms of noise pollution, such as residential, medical, educational centers, etc., and measuring sound in sensitive points as sound receptors, 5- modeling by TNM 2.5 software, AutoCAD map or GIS layers for the scope of the project should be prepared and converted to DXF format, 6- statistical analysis and comparison of the results obtained through the model and measurements and comparison with the standards, and 7- testing the hypotheses through SPSS statistical software and analyzing the results in the Excel environment.
The estimated results of the FHWA model were very close to the observed values (The highest value is 85 db and the lowest value is 55 db), therefore, according to the results of this model, it is reasonably accurate for predicting noise pollution, and the average difference of the Leq values calculated with the measured values is ±3.5 dB. The regression coefficient between the measured values and the values calculated by the model was reported as 0.685. The amount of difference of the predicted values is relatively high only in three stations 1, 7 and 24 and is equal to 14.8, 10.7 and 10.7 dB respectively. In examining the cause of this issue, it can be stated that two stations 1 and 7 are located in a position where, in addition to the sound they receive from the studied highway, they are affected by the traffic of vehicles on other routes near them and receive sound. In the study area, due to the fact that the majority of uses are residential, which is considered as a sensitive area, all measured values in the stations were higher than the standard of the Environmental Protection Organization (55 db). The lowest recorded sound is related to station number 36 with a level of 55.4 dB. This station is located inside the barren lands and is connected to the agricultural lands located between Amirieh and Esmatiye boulevards. The average amount of noise pollution in all stations is 74. The highest sound value is related to station number 24 and is equal to 85.1 dB, which is located at the beginning of Hashemi Street 45 and the dominant use around it is residential. Due to the large number of vehicles, including cars, heavy vehicles, buses, semi-heavy and motorcycles, all areas show high noise pollution that can endanger the health of citizens. The effect of car type was investigated by Pearson's test, and there was the highest correlation between motorcycles and noise pollution, as the number of motorcycles increased, the value of the two noise indices LAeq and LAFmn increased with correlation coefficients of 83% and 84%. In this regard, it is necessary to take necessary measures such as replacing with new electric motorcycles. Allocation of land around highways to sensitive uses, including medical and educational centers, has not been approved, and the effects of noise pollution can be reduced through appropriate planning. There are several solutions to reduce the effects of noise pollution, based on priority, it is possible to correctly locate the uses, consider the distance between highways and sensitive uses, assign this distance to uses such as linear green space, footpaths and bicycles, the creation of barriers that reduce sound waves such as embankment, trees and finally the last priority of using technical equipment such as acoustic wall.
The following steps were implemented for this research: 1- collecting information about the volume and speed of traffic, 2- collecting information and characteristics related to the road such as road width, road type, surrounding land use map, green space around the highway, height and density of buildings around the highway, meteorological information such as temperature and humidity, 4- determining sensitive points around the area in terms of noise pollution, such as residential, medical, educational centers, etc., and measuring sound in sensitive points as sound receptors, 5- modeling by TNM 2.5 software, AutoCAD map or GIS layers for the scope of the project should be prepared and converted to DXF format, 6- statistical analysis and comparison of the results obtained through the model and measurements and comparison with the standards, and 7- testing the hypotheses through SPSS statistical software and analyzing the results in the Excel environment.
The estimated results of the FHWA model were very close to the observed values (The highest value is 85 db and the lowest value is 55 db), therefore, according to the results of this model, it is reasonably accurate for predicting noise pollution, and the average difference of the Leq values calculated with the measured values is ±3.5 dB. The regression coefficient between the measured values and the values calculated by the model was reported as 0.685. The amount of difference of the predicted values is relatively high only in three stations 1, 7 and 24 and is equal to 14.8, 10.7 and 10.7 dB respectively. In examining the cause of this issue, it can be stated that two stations 1 and 7 are located in a position where, in addition to the sound they receive from the studied highway, they are affected by the traffic of vehicles on other routes near them and receive sound. In the study area, due to the fact that the majority of uses are residential, which is considered as a sensitive area, all measured values in the stations were higher than the standard of the Environmental Protection Organization (55 db). The lowest recorded sound is related to station number 36 with a level of 55.4 dB. This station is located inside the barren lands and is connected to the agricultural lands located between Amirieh and Esmatiye boulevards. The average amount of noise pollution in all stations is 74. The highest sound value is related to station number 24 and is equal to 85.1 dB, which is located at the beginning of Hashemi Street 45 and the dominant use around it is residential. Due to the large number of vehicles, including cars, heavy vehicles, buses, semi-heavy and motorcycles, all areas show high noise pollution that can endanger the health of citizens. The effect of car type was investigated by Pearson's test, and there was the highest correlation between motorcycles and noise pollution, as the number of motorcycles increased, the value of the two noise indices LAeq and LAFmn increased with correlation coefficients of 83% and 84%. In this regard, it is necessary to take necessary measures such as replacing with new electric motorcycles. Allocation of land around highways to sensitive uses, including medical and educational centers, has not been approved, and the effects of noise pollution can be reduced through appropriate planning. There are several solutions to reduce the effects of noise pollution, based on priority, it is possible to correctly locate the uses, consider the distance between highways and sensitive uses, assign this distance to uses such as linear green space, footpaths and bicycles, the creation of barriers that reduce sound waves such as embankment, trees and finally the last priority of using technical equipment such as acoustic wall.
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