Spatial modelling of railway noise propagation

In recent decades, population growth and progress of technology have shaped large and compact urban settlements. Existence of huge transportation systems and developed urban infrastructures are among the most important properties of modern cities. In spite of prompt transit and facilitated daily activities, development of transportation systems causes many problems, including traffic, air and noise pollutionand so on. Noise pollution as one of the most important human health threats can cause annoyance, sleep disturbance, decreased learning ability and even cardiovascular problems and blood pressure in long time. Sound is caused by a wide range of activities and processes. Road traffic, railways, airplanes landing, workrooms, industries and communicate places are the most important noise sources. Awareness of the noise emission status in urban environments and the identification of people at risk are primary steps that should be taken in planning as a basic information to reduce vulnerability. Currently, trains running along railways, after traffic jams, are ecoming the crucial  source of noise pollution. This is especially important in a large city such as Tehran, which crosses the rails a long way in residential areas. In this study, a spatial approach was used to model the noise pollution caused by railway transport in Tehran. To this end, the RMR standard was used to calculate the noise level generated in the source of sound (rail path). The noise emission and its attenuation in the environment was also modeled based on the method presented in ISO 9613-2. According to the results, the railway noise range in the studied area varies from 43 to 88 dB. The comparison of the estimated noise level with the measured values indicates a 3.5 dB RMSE. The overlapping of the noise map with the demographic data indicates that around 200,000 people are exposed to noise pollution of more than 70 dB and about 730,000 are exposed to noise pollution greater than 60 dB. Obviously, in the absence of proper residential insulation, the health of a large population of residents adjacent to the railway is at serious risk.