Road Tab
Information on the calculation options for the following standards or guidelines for industry can be found in the German version of the CadnaA reference manual:
- RLS-19 (Germany)
- RVS 4.02 (Austria)
- StL-86 (Switzerland)
- DIN 18005 (1987, Germany)
- SonROAD18 (Switzerland)
Table „Propagation Models Road“
The subsequent table lists the main characteristics of the propagation models for road noise as treated in the chapters explaining the configuration options. A special focus is put to the type of modeling being used for the various attenuating effects in sound propagation.
| No | Option or Propagation Effect | Standard / Guideline | |||||||||
| RLS-90 (1990) | Nordic (1996) | NMPB (1996) | CRTN | TNM | Czech Method | SonRoad | NMPB (2008) | CNOSSOS-EU | SonROAD18 | ||
| 1 | calculation using A-weighted levels | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes |
| 2 | spectral calculation | no | no | yes (octaves, 125 to 4000 Hz) | no | yes(1/3 octaves) | no | yes (1/3 octaves) | yes (1/3 octaves, 100 to 5000 Hz) | yes (for octaves 63 Hz to 8000 Hz) | yes (for octaves 63 Hz to 8000 Hz) |
| 3 | geometrical attenuation (divergence) | line source propagation (includes air absorption) | LAeq/LAFmax: line/point source propagation | point source propagation (4π r2) | in CadnaA: segmented line source | point source propagation (4π r2) | point source propagation (4π r2) | point source propagation (4π r2) | point source propagation (4π r2) | point source propagation (4π r2) | point source propagation (acc. to ISO 9613-2) |
| 4 | attenuation by air absorption | considered within the geometrical attenuation | not considered | yes (for 15°C and 70% r.h.) | not considered | acc. ISO 9613-1 (e.g. 20°C, 50%) | combined with ground att. | acc. ISO 9613-1 (for 15°C, 70%) | acc. ISO 9613-1 (for 15°C, 70%) | yes (acc. to ISO 9613-1) | yes (acc. to ISO 9613-1) |
| 5 | handling of ground reflections | considering ground attenuation and meteo effects in common (see below) | concept of reflection planes | algorithmic, not by image sources | algorithmic, not by image sources | complex ground impedance | algorithmic, not by image sources | complex ground impedance | algorithmic, not by image sources | algorithmic incl. ground absorp. | close to source reflections included in emission, else ISO 9613-2 (1996) |
| 6 | handling of reflections at obstacles |
up to 1st order, higher orders by a „Correction for multiple Reflections“, optionally: calculation to up the 20th order (condition from obstacle’s size and absorpt. coefficient/reflection loss of the reflector) | see RLS-90 | no mult. reflect. correction by default, optional in CadnaA | not using image sources (optional in CadnaA) | in CadnaA: via absorption coeff./reflect. loss of reflector | see RLS-90 | using complex reflection factor & phase relation | no mult. reflect. correction by default, optional in CadnaA | yes | up the 20th order (using reflection condition), optionally: „Correction for multiple Reflections“ acc. to RLS-90 |
| 7 | attenuation due to ground effect (ground attenuation) | for A-weighted levels (not applying ground factor G) | soft or hard ground only(combined with screening) | spectral model (for favorable: ISO 9613-2, for homogeneous specific) | empirical correction | via transfer table from airflow resistivity σ to ground factor G | combined ground and meteorological correction | via transfer table from airflow resistivity σ to ground factor G | spectral model (for favorable: ISO 9613-2, for homogeneous specific | homogeneous & favorable conditions using ground factor G | spectral model ground att. model (using ground factor G) acc. to ISO 9613-2 (1996) |
| 8 | attenuation due to screening (at objects) |
single + double diffraction based on the path length difference, just for A-weighted levels, negative path difference causes no screening, NOTE - „acoustical transparency“ of buildings not available | concept of effective height | based on path length difference | based on path length difference | diffraction model using Fresnel-zones & complex ground impedance | see RLS-90 | using path length difference (ISO 9613-2 (1996)), ground refl. based on Fresnel-zones | based on path length difference | single & double diffr., includes ground effect, using image source method | acc. to ISO 9613-2 (1996) |
| 9 | handling of lateral diffraction | not considered, in CadnaA optionally available | not considered | not considered | not considered | not considered | see RLS-90 | not considered | not expressively considered | not considered (for the time being) | acc. to ISO 9613-2 (1996) |
| 10 | handling of multiple obstacles in ray path | based on the path length difference of the direct path across all obstacles („ribbon band method“) | using the most efficient screen | see RLS-90 | inverse energetic sum of individual barrier corrections | via path length difference | see RLS-90 | via path length difference | via path length difference | via path length difference (convex hull) | acc. to ISO 9613-2, with more than one obstacle „ribbon band method“ |
| 11 | attenuation due to screening (terrain) |
screening by terrain not treated explicitly, In CadnaA the algorithm for multiple screening objects is applied. |
as with multiple screens | see RLS-90 | as with multiple screens (no lateral diffraction) | as with multiple screens | see RLS-90 | as with multiple screens | as with multiple screens | see ISO 9613-2 | as with multiple screens (no lateral diffraction) |
| 12 | handling of meteorological effects (wind) |
is part of the ground attenuation (meteo. correction), optional: with Cmet accord. to ISO 9613-2, calculations acc. to VBUS applies Cmet with C0,D/E/N=2/1/0 dB | not available | for homogeneous & favorable prop. cond., energetic addition | not available | not available | not available, optional in CadnaA: using Cmet | for homogeneous & favorable prop. cond. (see NMPB) | for homogeneous & favorable prop. cond., energetic addition | for homogeneous & favorable prop. cond., energetic addition | see CNOSSOS-EU |
| 13 | attenuation due to foliage | not considered, in CadnaA optionally accord. to VDI 2714 | not available | not available | not available | in CadnaA not available | not available | available | not available | not available | if propagation according to ISO 9613-2 (1996), then acc. to annex. A |
| 14 | attenuation due to built-up areas | not considered, in CadnaA optionally accord. to VDI 2714 | not available | not available | not available | in CadnaA not available | not available | not available | not available | not available | not available |
Table „Obstacles and Special-Objects“
A further table describes the properties of obstacles and special-objects in CadnaA with each propagation model.
| No | Object Type/ Option | Standard / Guideline | |||||||||
| RLS-90 | Nordic (1996) | NMPB (1996) | CRTN | TNM | Czech Method | SonRoad | NMPB (2008) | CNOSSOS-EU | SonROAD18 | ||
| 1 | building | single + multiple diffraction based on the shortest path difference, no lateral diffraction by default, no reflection or by input of absorption coefficient/reflection loss, no acoustical transparency | see RLS-90 | see RLS-90 | see RLS-90 | numerical diffraction model | see RLS-90 | numerical diffraction model | see RLS-90 | see RLS-90, but for homogeneous & favorable conditions | see CNOSSOS-EU |
| 2 | cylinder | single + multiple diffraction based on the shortest path difference, no lateral diffraction by default, no reflection or by input of absorption coefficient/reflection loss, reflection up to 1st order | see RLS-90 | see RLS-90 | see RLS-90 | see above | see RLS-90 | see above | see RLS-90 | for homogeneous & favorable conditions | see CNOSSOS-EU |
| 3 | barrier | single + multiple diffraction for edges based on the shortest path difference, no lateral diffraction by default, no reflection or by input of absorption coefficient/reflection loss | see RLS-90 | see RLS-90 | see RLS-90 | see above | see RLS-90 | see above | see RLS-90 | see RLS-90, but for homog. & favorable cond. | see CNOSSOS-EU |
| 4 | floating barrier | no diffraction around the lower edge, otherwise see barrier | see RLS-90 | see RLS-90 | see RLS-90 | not available | see RLS-90 | not available | see RLS-90 | see RLS-90 | see RLS-90 |
| 5 | barrier with cantilever | cantilever is totally absorbing (no reflection), calculation of the path length difference valid for receivers/grid points outside and below the cantilever, otherwise see barrier | not available (due to „effective height“ concept) | not available | not available | not available | not available | not available | not available | see RLS-90 | acc. to ISO 9613-2 |
| 6 | bridge plate | diffraction calculation for horizontal plate only, screening calculation for diffraction downwards, no reflection-induced level increase below the bridge plate (as ground is not modeled by mirror sources) | see RLS-90 | see RLS-90 | see RLS-90 | available | see RLS-90 | available | see RLS-90 | see RLS-90 | see RLS-90 |
| 7 | embankment | acts as a double barrier, diffraction for direct path (without lateral diffraction), no absorptive/reflective properties, NOTE - The embankment is not considered in the triangulation! | see RLS-90 | see RLS-90 | see RLS-90 | available | see RLS-90 | available | see RLS-90 | see RLS-90 | see RLS-90 |
| 8 | ground absorption area | not relevant (generalized ground attenuation) | in CadnaA: using ground factor G (soft/hard only) | using ground factor G (for favorable and homogeneous) | empirical ground correction (chart) | from ground factor G transferred to airflow resistivity σ | not relevant | from ground factor G transferred to airflow resistivity σ | using ground factor G (for favorable and homogeneous) | yes, using ground factor G (for favorable and homogeneous) | see CNOSSOS-EU |
| 9 | built-up area/foliage | not relevant by default, optionally accord. to VDI 2714 | not available | not available | not available | not available in CadnaA (for the time being) | not available | not available in CadnaA (for the time being) | not available | no effect | no effect |
| 10 | 3D-reflector | screening by shortest path length difference + 2 lateral paths, diffraction can be suppressed for up to 32 edges, reflection up to 1st order, no summation of diffraction effects via multiple edges, no multiple diffraction | not available (due to „effective height“ concept) | see RLS-90 | see RLS-90 | not available (not compatible with TNM diffraction model) | see RLS-90 | not available | see RLS-90 | see RLS-90 | no effect |
| 11 | self screening | additional feature in CadnaA: causes screening effect downwards, additional with left/right available (fixed to the road, screening just for the own road source) | see RLS-90 | see RLS-90 | see RLS-90 | not available (not covered by TNM diffract. model) | see RLS-90 | available | see RLS-90 | see RLS-90 | see RLS-90 |
| 12 | additional width/parapet L/R | parapet left/right available, parapet length can be restricted using station marks, additional width just for ground absorption with no effect with RSL-90 | see RLS-90 | see RLS-90 | see RLS-90 | available (used to apply correct road width) | see RLS-90 | available | see RLS-90 | see RLS-90 | see RLS-90 |