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Ground Absorption Areas

The object „ground absorption“ causes an attenuation

  • if the selected standard or guideline (see Standards) applies the ground factor G,
  • or a different parameter is used to specify the dampening effect of the ground which can be transferred into an appropriate value of the ground factor G.
  • When a standard or guideline includes several, different ground attenuation models a further selection on the relevant configuration tab for the a specific source type may be required (e.g. see ISO 9613 (1996)).

For more information regarding the guideline-specific procedures for calculating ground attenuation see Industry Tab, Road Tab, and Railroad Tab.

In case the selected standard or guideline applies a generalized ground attenuation model - i.e. the ground attenuation does not depend on the local ground properties, but is just determined from the ray‘s geometry - the object „ground absorption“ does not cause any damping effect.

Dialog options

Name, Memo-Window, ID, ObjectTree, Master

see Dialog Options Name, ID, INFO, ObjectTree, Master in the manual "Introduction to CadnaA"

Ground Absorption G

value of the ground factor G, default value G=0

Object‘s Geometry

The object is entered as a closed polygon with the height specified - if any - on the dialog Polygon: Geometry is not relevant.

With multiple ground absorption areas overlapping each other, the area on top represents the overlap region. This is equal to a lower position of the respective absorption area in the table Ground Absorption (see Tables| Obstacles menu).

Special Case: Road & Rail

In conjunction with the self-screening option for the objects „Road“ and „Railway“ an additional width can be entered specifying the ground absorptive properties within the road or railway track area (see Common Input Data and Common Input Data, both Only for Ground Absorption, no Screening).

„Ground Absorption“ tab

see Calculation|Configuration menu, „Ground Absorption“ tab (see Ground Absorption Tab)

Default Ground Absorption

This value specifies the ground factor G for areas not covered by the object „Ground Absorption“ (default value 1, range 0<=G<=1).

Option „Use Map of Ground Absorption“

This option enables - in case numerous ground absorption areas - to reduce the calculation time by generating a map of ground absorption areas.