Reflections of Higher Order

In calculating reflections of second order all valid mirror-sources have to be reflected again on all reflecting areas to prove the validity of each reflection and to calculate the corresponding path of the ray.

The number of rays with a further order of reflection results from the product of the number of reflections from the last order multiplied by the number of valid reflectors. The specification of this numeric method is found in Pro-1988.

It is obvious that the number of possible reflections explodes with an increasing number of orders. Calculations up to higher orders are only completely possible for very restricted arrangements. On the other hand, a reflection has to be calculated first before its contribution can be evaluated as irrelevant.

CadnaA enables the calculation of reflections of high orders for all type of sources. The paths of ray can be displayed and the sound level contributions of the reflections are separately identified. According to the specifications of the standards for the source type Road and Railway with activating these standards only reflection of first order are calculated using mirror-image method - reflections of higher order are taken into account with a penalty for multiple reflections.

An example for the complete calculation of reflection up to the 10. order is shown with the backyard in the next figure. A point source located in front of the opening beams into the backyard, and the sound level shall be calculated at the represented receiver IP.

All ray paths for each reflection order in a backyard

All possible ray paths of rays in a calculation up to the 10. order

Arbitrary arrangements of objects can be taken into account for a calculation of reflections. With this technique it is possible to perform the calculation of the sound level corresponding to the reality in cases not corresponding to the valid guidelines.