Calculation accuracy

It is important to be aware that even though input data are given as accurately as possible, there will always be a certain insecurity in a noise calculation. Noise values close to limits that decide if measures should be taken, should therefore be specifically considered for inaccuracies.

Inaccuracies in the calculations results can be caused by:

Inaccuracy in input data

Examples of inaccuracies in input data are:

The figure to the right shows how big difference small inaccuracies can make.

A: An inaccuracy of maybe only a few centimeters gives this terrain.

B: Correct terrain

a: Noise source

b: Sight line

c: Calculation point

A major question when calculating the noise along a noise profile with the Nordic method, is whether there is a barrier along the profile. The difference between having a barrier or not is quite big (close to 3dBA). However, this will normally be leveled out, since there are many profiles calculated for each calculation point.

Studies show that the deviation between measured values and calculated values normally are within +- 1dBA.

Inaccuracies in the calculation method

There are limits in the Nordic calculation methods. One example is that it calculates only one "barrier" for each terrain profile. If there is both a local noise barrier and a barrier close to the road, the effect will not be calculated correctly. This is a scenario to keep in mind.

Inaccuracies in the implementation of the calculation method

Studies have shown that the calculations in Novapoint Noise are very close to what is calculated manually with the same method.