Line source

Line sources are used for sound sources that can be approximated by a continuous line.

Overview

Each Vehicle can contain any number of Line source objects, which include properties for their location and sound power.

Each of the Line sources are assigned a Line source library item, and in this way many Line sources can be reused throughout your project. Line sources can be added or deleted, by right-clicking on the appropriate items in the model objects view.

N.b. line sources are specified using sound power input files, with the input data given as dB re 1e-12W/m (i.e. per metre length).

Input Parameters

Name	Data type	Unit	Comment
Label	Text	-	A label for this Line source. This will be used to identify the Line 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.
Center distance from vehicle front	Number	m	The distance between the front of the Vehicle and the centre of the Line source.
Height above rail	Number	m	The vertical distance between the top of the rail and the Line source.
Lateral distance from track centre	Number	m	The horizontal distance between the centre of the Track and the Line source. Positive values are towards the left from the perspective of a forward travelling train.
Length	Number	m	The length of this Line source implementation.
Max. point spacing	Number	m	In the calculation, the Line source is approximated by distributed point sources; here it is possible to specify the maximum spacing between these point sources. It is recommended that this should be less than half the closest distance between the source and receiver. Note that in the calculation, the Line source will always be represented by a minimum of three point sources.
Source grouping	Lib. item	-	The Source group that this Line source belongs to.
Library item	Lib. item	-	The library item for the Line source.
Sound power input file	File	-	This is the file location for the Line source sound power (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 1⁄3 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.