# Noise contours cross barriers

When you make noise contour lines or noise contour surfaces, these are calculated solely on basis of already calculated noise calculation points. Values between these points are calculated by linear interpolation.

This can give strange looking results if the calculation points are not created with any regard to this.

In the picture above you see that the red noise surface area is not broken by the (black) noise barrier, as one would expect. Now turn off the surfaces and create contour lines instead:

In this view, you see that there are 7 visible noise calculation points (5 red and 2 yellow). The 4 rightmost red ones surround the right end of the noise barrier, leaving all the area between them red, since the whole square between these 4 points will be colored red.

How to improve this?

It is quite simple to improve this. Just use the function "Several new calculation points":

Enter the names, calculation heights etc you want for these points and click in the drawing, on both side of all barriers, close to the barriers. As you can see, you do not need to have any specific distance between the points.

Then you need to run a new calculation for these points. If you do not want to recalculate the already calculated points, see: Calculating only uncalculated pointsÂ

When the calculation is done, create new noise contour surfaces and things should look better:

You might want to iterate the process with more points, if the results still are odd.