Railway Noise Module
SoundPLAN was chosen for the END train noise map for all of Germany. 

What does this module do? Calculate the noise levels at specific receivers and noise maps caused by trains passing on the railways. Noise levels can be of the type Leq and Lmax. What Standards are supported?

The Railway Noise ModuleThe SoundPLAN railway noise module is split into 2 sections, the first calculates the emissions and assigns them to a track, the second then calculates the noise levels for all receivers. There are provisions for Stand Alone Receivers and for Grid Noise Map, Facade Noise Map, CrossSectional Noise Map and the Meshed Noise Map. If the noise levels exceeds the noise limit, noise protection walls are the preferred method of noise control. The optimization of berms and noise protection walls is described in the module WallDesign. You can select any of the standards on the left for your work but must understand that for railway noise (and also for road noise) the emissions are standard specific and it is not possible to enter the railway track for one standard and then calculate the noise levels at the receiver for another one. Railway noise is calculated with the Leq for whatever time slots are chosen in the noise assessment, the calculation of the Lmax is also possible. 


Emission Calculation As the calculation of the emission is standards dependant, this overview can only show one example, it is taken from the WINCITY project and features the German Schall03. Train tracks seldom only have one type of trains, therefore the train emissions provide the possibility to enter different trains from a train setup which SoundPLAN is delivered with but is fully customizable. For each train, the number of trains for a given time slot (day/night or day/evening/night) needs to be entered, the length of the train and other data come from the library but can be altered. For each of the trains the emission level is calculated for the Leq, the sum of all trains for each time slot is also listed. The emission level for trains does not only depend on the train type and speed but also has additions for the type of ballast bed, the squeal in curves, multiple reflections, railroad level crossings and bridges. In addition to the Leq, the Lmax can be calculated for trains but the noise assessment must have provisions for it (an extra time slot for Lmax) and you must select which train to use for the Lmax calculation.


One Railway, many Definitions Railway objects are variant objects so new definitions can be entered at any coordinate along the track. For a bridge, a level crossing or ballast bed or curve squeal or a change in speed on the railway, you do not have to create a new object, simply click on the coordinate where the change occurs and enter a new definition which then will be valid until it is replaced by a new definition. 


Bridges
Bridges are structures where the noise can pass underneath. The noise from traffic on the bridge itself is shielded by the edge of the bridge surface or the solid barrier on the side. These parameters are assigned to the road itself. For big noise maps it can be tedious to find the bridges, so SoundPLAN has implemented an algorithm to automatically detect the bridges from the terrain information around it. Mark the roads you want to detect bridges on and start GeoTools/more elevation tools/bridge detection you can enter into a search to find bridges = anormalities in the terrain. The height of the bridge edge then is a bit of a manual adjustment.


Noise from Railway Tunnels Noise from railway (and also road) tunnels must be treated in a special way. Unlike regular railway noise where the emission is on the railhead, noise from tunnels is emitted over the entire mouth of the tunnel. Depending on the absorptive characteristic of the tunnel walls, the frequencies shift to the lower frequencies, and the noise is emitted with a directivity. All these factors are included in the SoundPLAN object for tunnels. See also the ppt for noise from tunnels 

Calculating the Lmax As the train cannot be treated as a point source but is a moving line source of a defined length, the calculation of the Lmax is just doing this, it assumes a start position on the track and with the train speed and all the other parameters calculates the noise level for the receiver. After the calculation, the train moves to the next position that it would assume in 0.2 seconds. Here the next noise level calculation is carried out. This loop goes on until the train has reached the end of the line. The calculation of the instant noise level is complicated because with the length of the train it is no possible to ignore the fact that the direct and the reflected noise components may arrive at the receiver at different times, thus the speed of sound matters. The sound levels from the entire train pass by is collected in a table and the program searches for the maximum value. The data also can be stored and opened up from the SoundPLAN Graphics to present the LevelTimeChart and also to create the Animated Noise Map. 

The Animated Noise Map The Animated Noise Map is producing a noise map for all receivers for the time T=0.0 then advances the timer and produces the next noise map for T=0.2 and so on. This movie can be recorded to an uncompressed AVI file but keep in mind that these uncompressed files can get very large vary quickly. This module requires the Graphics Animations module to be present in the license. 


Results Where? What? Aside from the customary Grid and Facade Noise Maps the SoundPLAN Result Tables offer more insight for Single Point Sound Receivers. On the left you can see the time/level chart of a train pass by, you can also get the "normal" level diagrams that show from which direction the direct noise and the reflected components were received. In addition to the receiver information, a documentation of the tracks and the trains is available. 
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