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A Receiver type simulation, parameterized with a Signature(rail) storage mode, makes it possible to obtain the acoustic signature of the trains as well as various dynamic indicators (TEL, SEL, LAmax,S, LeqTp) (see Signature window).

A Horizontal, Facade or Vertical type simulation, configured with an LAmax(rail) storage mode, allows you to create maps using LAmax type indicators.

To obtain relevant results, the model must be parameterized according to precise principles.

Describe noise sources with complete convoys

In order to correctly calculate the dynamic indicators, it is necessary to describe the traffic with complete convoys and not per unit. The decomposition of trains into units has no impact on the calculation of the Leq but strongly influences the calculation of dynamic indicators at distances from the railway greater than the length of the units.

In particular:

•Dynamic indicators depending on the ratio train length / distance from the railway

•The LAmax,S is not the same for a TGV-UM (multiple unit with a length of 400 m) as for two TGV-US (single unit with a lenght of 200 m) which follow one another at 5 minutes apart.

•For freight, it is imperative to compose complete trains with their locomotive(s) and their wagons.

•The same goes for regional trains based on individual Corail type cars (towed by electric or diesel locomotives).

Merge Railway objects representing the same railway

The acoustic signature and the dynamic indicators are calculated independently for each Railway object.

In MithraSIG, railways are very often broken down into several sections (Railway objects). In order to calculate the acoustic signature of the trains, it is therefore necessary to join the sections having the same emissions (same trains, same speeds). This can be done using the Join Lines tool available at right click after selecting the axes of the Railway objects to merge.

Configure the calculation with Beam mode

Configuring the tracer of the calculation in Beam mode makes it possible to greatly increase the discretization of the sources while ensuring that no source is missed.

Impact of periods

Rail traffic (and therefore Leq levels) varies depending on the time of day. We assume that the dynamic indicators do not depend on the period. Indeed, insofar as we want to characterize the maximum exposure over short periods, we assume that this always corresponds to favorable propagation conditions (therefore without weighting by weather conditions). For a given train, at a given speed, the indicators are therefore independent of the period of the day and/or night. The only thing that can depend on the time is therefore the presence or absence of a type of train and/or the speed of it.