Noise Contour Lines

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MOUS_ICO Menu: Noise> Noise contour lines

This dialog box allows you to calculate noise contour lines and to color the areas between the noise contour lines according to the calculated noise levels. Before this may be done, a regular calculation must be carried out for all calculation points to be included in the basis for the generation of the noise contour lines.

A triangle model is created from the calculation points, where the calculated noise levels are used as z-values. The noise contour lines are generated from this triangle model.

In theory, it is possible to generate noise contour lines based on the calculated noise levels for only three calculation points. To generate meaningful noise level contour lines, a network of calculation points must be included. The closer the calculation points are located, the higher the accuracy of the noise level contour lines. The complexity of the terrain surface, number of buildings, and number of barriers will influence the required density of the calculation points. We recommend the following:

• 5-10 m between points when the terrain is complex, there are many buildings and possibly barriers

• 10-20 m between points when the terrain is medium complex, there are some buildings and possibly some barriers

• 20-40 m when the terrain is fairly even and there are a few buildings/barriers

The calculation points do not have to form a grid. Which calculation points to include in the generation of the noise contour lines is decided by the choices made within the frame Selection of calculation points in the dialog box.

It is important to be aware that even though the noise contour lines are generated from a fairly dense network of calculation points, some local variations may be missing. Thus, in “messy” areas, extra calculation points should be added.

Make sure that none of the calculation points to be included in the generation of noise contour lines are located on top of buildings, or have an otherwise unfortunate location. Such points must be moved or deleted before the calculation starts. When defining calculation points in the dialog box vnnp_noisecalculationpointgrid, the location of points on top of buildings can be avoided by setting the alternative Do not create points within buildings.

If noise contour lines are to be generated for separate areas, these should be generated separately. This is to avoid generating contour lines between the areas.

Generation of noise contour lines and noise surfaces are one-way operations. They are not automatically updated if one performs new calculations, defines more calculation points, etc.

Selection of calculation points

Here the user selects which calculation points to include in the generation of noise contour lines.

• only active, calculated points - The noise contour lines will disregard passive calculation points. Use the selection possibilities in the dialog box vnnp_noisecalculationpoints to filter out points that are to be disregarded.

• all calculated points - Uses values from all calculation points, even passive ones.

• Max. noise value - Uses the highest calculated value for the point, no matter for which floor it is calculated.

• Floor with height - Uses the value calculated for the height given in the box to the right of this field. Calculation points not having any floor with this height will be disregarded.

• Floor - Uses the value calculated for the floor given in the box to the right of this field. Calculation points not having any floor with this number will be disregarded. Note that there will be no control of whether all floors have the same height, the only thing checked is the floor number!

• Restrict area - Restrict the area in which the noise contour lines are to be drawn. Contour lines and noise level areas will be trimmed so they do not exceed the selected polygon.

• Select boundary line < - All dialog boxes are closed, and you get the opportunity to select a polygon in the drawing. As we click a polygon on the screen, we return to the dialog box.

• Draw boundary line <  - All dialog boxes are closed, and you get the opportunity to draw a polygon. By pressing <Enter> you get back to the dialog box.

Noise contour lines

• Create noise contour lines - Create noise contour lines when OK is pressed.

• from - The lowest dBA value for which to draw a contour line.

• to - The highest dBA value for which to draw a contour line.

• with interval: - How large dBA value there is to be between contour lines.

  • The values appearing in the data fields from:, to: and with interval: are taken from the value type selected for the Color scale…. These values are just suggestions and may be changed.

• Write noise values on contour lines - Write dBA values along the contour lines.

• every - The number of meters along the contour lines between each time the line is broken to write the dBA value.

• Text height - The height of the text for the dBA values.

• Choose layer - The layer for the created noise contour lines. The selected layer is shown to the right of the button. If you click the button, a list of all layers in the drawing will appear. Here you may choose between existing layers in the drawing, or you may create a new layer by entering the desired layer name in the data field at the bottom of the dialog box.

• Color - Opens the AutoCAD dialog box Select Color. Here you may select colors for noise contour lines.

Noise level areas

• Create colored areas according to the color scale - Create coloured noise areas. The objects that together shape the areas are collected into an anonymous GROUP in AutoCAD, to enable them to be handled as one object.

• Choose layer - The layer for the created noise level areas. The selected layer is shown to the right of the button. If you click the button, a list of all layers in the drawing will appear. Here you may choose between existing layers in the drawing, or you may create a new layer by entering the desired layer name in the data field at the bottom of the dialog box.

• Color scale - Opens the dialog box vnnp_noisecolorscalestyle. Note that the settings done for colour scale from the dialog box for noise contour lines do not have any influence on the colour scale settings for calculation points and buildings!

• SOLID - Generate the areas as SOLID objects in AutoCAD. This gives totally covered coloured areas.

• 3DFACE - Generate the areas as 3DFACE objects in AutoCAD. These are real 3D objects in AutoCAD.

Misc.

• OK - The dialog box is closed and noise contour lines and/or noise level areas are calculated and drawn, the text is possibly printed to noise contour lines, and noise level areas are coloured, depending on the selections made. A question will appear asking whether or not to copy the map upon the areas. If one wishes to see the map of the coloured areas, one has to answer yes. In vnnp_noiseoptions one may choose not to have to answer this question.

• Cancel - The dialog box is closed without generating noise contour lines or noise level areas.

Next topic: External Calculation