Chapter 6 - Calculation

CadnaA enables

• the calculation of sound propagation according to standardized procedures

and

• with settings that are defined by the user.

This chapter deals with the second task and its possibilities with CadnaA and is therefore more concerned with the physical aspects of sound propagation. This is very important because CadnaA is used for expert work, in scientific work at universities and in lectures. Although the professional usage requires a strict application of the procedures fixed by standards and guidelines, it can be very useful the be able to process special calculation tasks which are not covered by the regulations in detail.

Especially, this concerns the handling of reflections with higher order. According to the standard procedures a reflection of the first order is only dealt with according to the mirror image method, So just a single reflection of a ray at a flat surface. In case more orders of reflections contribute to the total result (e.g. at the building facades on both sides of a road), this will be taken into account - in the majority of road and railway noise standards - by calculating analytically a correction for multiple reflections from the geometrical and acoustic parameters.

This strategy fails if the geometry of the building lateral to the road is completely different and varies from building to building. The same problem exists with the noise level in backyard locations. Those cases can just be treated by calculating higher orders of reflection.