Chapter 3 - Obstacles
In CadnaA, the following types of objects cause a screening effect in the calculation of propagation, depending on the standard or guideline selected for each noise type:
- building
- cylinder
- barrier
- bridge
- embankment
- ground absorption area
- built-up areas and foliage
- 3D-reflector
The following types of obstacles may also have reflecting properties:
- building
- cylinder
- barrier
- 3D-reflector
Reflection Properties
In order to specify the reflectivity of the surfaces of obstacles three options are available in CadnaA.
No Reflection
No reflection is calculated for this object. This is the default setting.
The subsequent options require that on dialog Calculation|Configuration, tab „Reflection“ (see Reflection Tab) at least the reflection order 1 has been selected.
Reflection Loss
Enter the reflection loss in dB due to reflection or click the file selector symbol to select from a predefined list of reflections types, i.e. surface classifications (resulting from RLS-90/Schall03(2014) or RLS-19).
Predefined reflection types
The reflection losses RL with these predefined classifications are:
| Publication | Surface Classification | RL (dB) |
| RLS-90 + Schall03 (2014) | Flat and hard Walls | 0 |
| Smooth Facade / reflecting Barrier | 1 | |
| Structured Facade | 2 | |
| Absorbing Barrier | 4 | |
| Highly Absorbing Barrier | 8 | |
| RLS-19 | Facades and reflecting Barriers | 0,5 |
| Absorbing Barriers | 3,0 | |
| Highly Absorbing Barriers | 5,0 |
Absorption Coefficient Alpha
With this option activated, a single-number value, a formula, or the reference to an absorption coefficient spectrum (see Absorption Spectra) can be specified.
Note
The reflection loss RL is evaluated from the absorption coefficient Alpha according to: \(RL=-10\lg(1-Alpha)\)