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Wall Optimization

CadnaA enables to determine automatically the required height of a noise barrier in order to respect a predefined limiting level using an iterative optimization calculation strategy. The object "Embankment" and not the "Barrier" must be used for this wall optimization, due to the internal object structure required. The embankments may be replaced with barriers when the calculations are optimized. To execute a wall optimization it is mandatory that a limiting level is assigned to the receiver points. The limiting level can either be enter directly or may be extracted from areas of designated use.

In the following example a noise barrier alongside of a road shall be optimized. This applies in the same way for other line sources (e.g. line source, railroad).

Entering Objects

  • Enter a road with the following emission data for CNOSSOS-EU procedure. The remaining input values on the dialog Road are kept.
    • road width: 3 meters,
    • MDTD = 10000 vehicles/24 and road type „national“
  • Enter a building on a side of the road having a height of 10 meters.
  • Select the command Object Snap (Options menu) and enter a snap radius of 10 pixels with a distance points-facade of 0.05 m
  • Enter a receiver at the building’s facade facing the road.
  • Double-click on the receiver point: The option „Determine from Areas of Land Use" is activated by default. Select from list box „Use Standard Values for“ the option „Roads“.

Defining Areas of Land Use

  • Define an area of land use around the building so that the receiver point is surrounded by the area (symbol: ).

  • Double-click on the border of the area of land use and select from the list box „Land Use“ the option „WA Allgemeines Wohngebiet“ (in English: residential area).

With this setting the reference values as defined on dialog Land Use for road noise (Options menu) apply.

Note

You may add your own definitions at the lower end of the list of land uses. On dialog Land Use click into an empty line in column „Land Use“ and enter corresponding limiting values for each noise type.

  • Start the calculation by a click on the pocket calculator symbol on the symbol bar.

Subsequently, the receiver point’s color switches to red (for performance parameter: Day = LP1). This means that the limiting value assigned to the receiver is exceeded for the day time period.

Limiting value for the receiver at the building exceeded

Note

If the receiver’s color does not turn to red, either the area of land use is missing or the sound pressure level at the receiver is too low in your case. Correct for this if necessary.

Parallel Object: Embankment

In the next step an embankment as a parallel object to the road is generated.

  • Select from the context menu of the road the command Parallel Object.
  • Choose the object type „Embankment" and activate the option „Left from active Object“.
  • Enter a distance of 5 m and a height offset of zero.

Dialog Parallel Object: generate parallel embankment

  • Double-click on the embankment and enter a slope of 1:0.

Note

By the slope of 1:0 a vertical embankment is predefined. The height is not entered since this is calculated on optimization.

  • Select from the context menu of the embankment the command Break into pieces and enter 10 meters for the length of each piece.
  • Select from the Options menu the command 3D-View.
  • Change the type of view to "General parallel" and choose a suitable angle of view by typing the left/right arrow keys on your keyboard.

  • Now, click the symbol for the wall optimization .

  • Keep the default optimization parameters (element height: 0.5 m, max. number of elements: 20). This corresponds to a maximum barrier height of 10 meters.

  • Start the wall optimization with OK.

At first, CadnaA checks whether the limiting value is kept at the embankment’s maximum height. The optimization is continued only if this is the case. Subsequently, with each iteration step there is a check to determine which of the embankment sections yields the highest level reduction.

This optimal section is then considered in the next iteration step. Finally, the optimization result is displayed graphically on dialog 3D-View.

Result of the wall optimization

The table Embankment (Tables|Obstacles menu) lists the height of each section.

Table Embankment listing the section heights

  • Move the dialog Embankment so that the road becomes fully visible. When clicking in a line of the table, the respective embankment section is highlighted.

Note

You may convert the embankments to barrier (via action „Convert to“) in order to consider reflections.