Area source

Area sources are used for sound sources that can be approximated by a flat rectangular area.


Each Vehicle can contain any number of Area source objects, which include properties for their location, geometry and sound power. Note that Area sources are assumed to be aligned with height in the vertical axis and a length in the track’s longitudinal axis, and zero width in the track’s lateral axis.

Each of the Area sources are assigned an Area source library item, and in this way many Area sources can be reused across your project. Area sources can be added or deleted, by right-clicking on the appropriate items in the model objects view . The order of the Area sources in the model objects view is determined by their distance from the front of the Vehicle.

Input Parameters

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Name Data type Unit Comment
Label Text - A label for this Area source. This will be used to identify the Area source in the calculation and results. Special characters are not allowed.
Enabled Checkbox - Specifies whether this source is enabled in the calculation. This is a convenient method to deactivate a single source without removing it from the model. Note that for a source to be active in the calculations, its Source grouping conditions must also be met.
Centre distance from vehicle front Number m The distance between the front of the Vehicle and the centre of the Area source.
Centre height above rail Number m The vertical distance between the top of the rail and the centre of the Area source.
Centre distance from track centre Number m The horizontal distance between the centre of the track and the centre of the Area source. Positive values are towards the left from the perspective of a forward travelling train.
Radiating direction Choice - Select to which side the Area source is radiating: ‘All’, ‘Left’ or ‘Right’.
Source grouping Lib. item - The Source group that this Area source belongs to.
Library item Lib. item - The library item for the Area source.
Area source length Number m The length of the Area source (in the track longitudinal direction).
Area source height Number m The height of the Area source (in the vertical direction).
Sound power input file File - The file location for the Area source sound power is specified here (with ’.txt’ file extension ).
Use narrowband auralisation Checkbox - Select to use a narrowband file for auralisation. This will take the narrowband data and shape it to fit the output 13 octave band results, applying Doppler shifts as necessary, and maintaining any tonal content.
Narrowband file File - If the option to use narrowband data for the auralisation was selected, this is the file to be used for the narrowband spectrum (with ’.txt’ file extension ).
Sound power mode Choice - Select whether the specified sound power is to be considered as ‘constant’ or ‘speed dependent’.
Input file speed Number km/h If the sound power has been selected as being ‘speed dependent’, this is the reference speed used for the specified sound power level.
Speed coefficient Number - If the sound power has been selected as being ‘speed dependent’, this is the speed coeefficient that will be used to apply a correction for the speed. For example, setting this to 30.0 will apply a 30.0 log10(v/v0) correction (where v and v0 are the train speed and reference input file speeds, respectively).
Insertion gain - - Here, manual corrections can be specified to increase or decrease the sound power level data used in the calculations. Clicking on the button will launch a dialog window to input this data as either a single value for all frequencies, or as a pasted spectrum of corrections (comma separated over the range 20-20,000 Hz). Corrections can also be adjusted for individual frequency bands.

In the calculations, each Area source is split into several sub-sources. If the radiating direction is set to ‘All’, then each sub-source has a monopole directivity. If the radiating direction is set to ‘Left’ or ‘Right’, then this is relative to the forward travelling train, and the sub-sources are assigned half-monopole directivities, with no noise radiated to the reverse side of the Area source. For more precise control over the noise emissions in different directions, consider using Box sources.