Question: I have used the 'Show Source Contribution' calculation options, and some road segments are not giving any contribution. Is this because there is a limit on the number of segments allowed in NoiseMap?
Answer: No! There is no limit to the number of any type of object in NoiseMap, within practical limits such as those given by the memory of the computer and calculation time. Certainly you can have tens of thousands of objects.
The reason some segments are not giving the expected noise contribution is that they are being ignored because the 'Cut-off angle' is too small. In fact, in your model, the road segments are too short because you have created them from digital maps to an accuracy of 0.1 metres, so some segments are only a few metres long.
Really, you shoud re-digitise with a slightly greater tolerance (0.5 m would usually be good enough). However, if you don't want to change your model, then set the cut-off angle [parameter>edit calculation parameters] to less than the default value of 1 degree, perhaps to 0.2 degrees. The downside is that calculation time may increase.
Roger
