Railroad 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:
- ONR 305011 (Austria)
- DIN 18005 (1987, Germany)
- Semibel (Switzerland)
Table „Propagation Models Railroad“
The subsequent table lists the main characteristics of the propagation models for railroad 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 | ||||||||
| Schall 03 (1990) | Schall 03 (2014) | Nordic (1996) | CRN | SRM II | NMPB-Fer (1996) | NMPB-Fer (2008) | FTA/FRA | CNOSSOS-EU | ||
| 1 | calculation using A-weighted levels | yes | yes | yes | yes | yes | see NMPB-Fer 1996 | yes | yes | yes |
| 2 | spectral calculation | no | yes | yes | no | yes(63 to 8000 Hz) | as above | yes (1/3 octaves, 100 to 5000 Hz) | no | yes (octaves 63 Hz to 8 kHz, + 31.5 Hz |
| 3 | geometrical attenuation (divergence) | half sphere (2π r2) with directivity | full sphere (4π r2) with directivity | full sphere (4π r2) | in CadnaA: segmented line source | segmented line source (distance & viewing angle) | as above | point source propagation (4π r2) | in CadnaA: segmented line source | point source propagation (4π r2) |
| 4 | attenuation by air absorption | yes (according to VDI 2714) | using air absorption accord. to ISO 9613-1 | yes (for 15°C, 70% RH) | not considered | yes (10°C, 80%), option: ISO 9613-2 | as above | acc. ISO 9613-1 (for 15°C, 70%) | not considered | yes (acc. to ISO 9613-1) |
| 5 | handling of ground reflections | not by image sources, but by an algorithm considering ground attenuation and meteorological effects in common (see below) | as above | algorithmic, not by image sources | algorithmic, not by image sources | algorithmic, not by image sources | as above | algorithmic, not by image sources | algorithmic, not by image sources | algorithmic incl. ground absorp. |
| 6 | handling of reflections at obstacles | just up to 1st order, higher orders applying a „Correction for multiple Reflections“, optionally: calculation to up 20th order, condition for reflection considers obstacle’s size and absorption coefficient/reflection loss of the reflector | as above, by default up to 3rd order (accord. to Sch03 2014) or up to 20th order | see Schall 03 (1990) | using a global correction, optional in CadnaA: using image sources | using image sources, absorption coeff./reflection loss of reflector | as above | no mult. reflect. correction by default, optional in CadnaA | using image sources, absorption coeff./reflection loss of reflector | yes |
| 7 | attenuation due to ground effect (ground attenuation) | for A-weighted levels (not applying ground factor G) | alternative procedure (for A-weighted levels) accord. to ISO 9613-2 (1996), deviating calculation procedure for water surfaces | complies with spectral ground attenuation model of ISO 9613-2 (1996) | empirical correction | spectral ground attenuation model applying ground factor G (similar to ISO 9613-2 (1996)) | as above | spectral model (for favorable: ISO 9613-2(1996), for homogeneous specific) | using ground factor G, in CadnaA: average height (acc. ISO 9613-2(1996)) | homogeneous & favorable conditions using ground factor G |
| 8 | attenuation due to screening (at objects) | single and double diffraction based on the path length difference of the direct path via the obstacle, screening effect does not depend on wavelength (as just for A-weighted levels), negative path difference cause no screening REMARK: „acoustical Transparency“ of buildings not available |
single & double diffraction using path difference, ray across obstacle w/o ground absorp., barrier attenuation depending on wavelength | concept of effective height | based on path length difference, negative path difference causes screening | concept of effective height | as above | based on path length difference | based on path length difference and source height | single & double diffr., includes ground effect, using image source method |
| 9 | handling of lateral diffraction | not considered, in CadnaA optionally available | with lateral diffr. (using two lat. paths + direct path) | not considered | not considered | not considered | as above | not expressively considered | not considered | not considered (for the time being) |
| 10 | handling of multiple obstacles in ray path | based on the path length difference of the direct path across all obstacles („ribbon band method“) | in CadnaA: applies „rubber band method“ to calculate path difference | using the most efficient screen | based on path length difference | concept of equivalent screens (instead of multiple diffraction) | as above | via path length difference | see Schall 03 (1990) | via path length difference (convex hull) |
| 11 | attenuation due to screening (terrain) | screening by terrain not treated explicitly. In CadnaA the algorithm for multiple screening objects is applied. | as above | as with multiple screens | as with multiple screens | as with multiple screens (no lateral diffraction) | as above | as with multiple screens | see Schall 03 (1990) | see ISO 9613-2 |
| 12 | handling of meteorological effects (wind) | not treated explicitly (meteorological correction is part of the screening calculation), optional: application of Cmet accord. to ISO 9613-2, with calculations acc. to VBUSch: applies Cmet with C0,D/E/N=2/1/0 dB | no | not available | not available | available using Cm (upper limit 3.5 dB), optional: Cmet acc. to ISO 9613-2 | as above | using occurrences of homogeneous and favorable propagation conditions | not considered | for homogeneous & favorable prop. cond., energetic addition |
| 13 | attenuation due to foliage | without screening calculation, but based on the length of the curved ray path (arc of a circle) passing through the foliage (with height h) assuming a radius of 5 km | not available | available | not available | not available | as above | not available | in CadnaA not available | not available |
| 14 | attenuation due to built-up areas | not considered, in CadnaA optionally accord. to VDI 2714 | not available | available | not available | not available | as above | not available | in CadnaA 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 | ||||||||
| Schall 03 (1990) | Schall 03 (2014) | Nordic (1996) | CRN | SRM II | NMPB-Fer (1996) | NMPB-Fer (2008) | FTA/FRA | CNOSSOS-EU | ||
| 1 | building | single & multiple diffraction using shortest path difference, no lateral diffraction by default, no reflection or by absorption coefficient/reflection loss, no acoustical transparency | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see NMPB-routes (1996), Road Tab | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990), but for homogeneous & favorable conditions |
| 2 | cylinder | single & multiple diffraction using shortest path difference, no lateral diffraction by default, no reflection or by input of absorption coefficient/reflection loss, reflection up to 1st order | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | as above | see Schall 03 (1990) | see Schall 03 (1990) | for homogeneous & favorable conditions |
| 3 | barrier | single & multiple diffraction using shortest path difference, no lateral diffraction by default, no reflection or by absorption coefficient/reflection loss | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | as above | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990), but for homog. & favorable cond. |
| 4 | floating barrier | no diffraction via the lower edge (screening edge without diffraction), otherwise see barrier | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | as above | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) |
| 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 | not available (due to „effective height“ concept) | available, using path length difference | not available (due to „effective height“ concept) | as above | not available | not available (just for vertical barriers) | see Schall 03 (1990) |
| 6 | bridge plate | diffraction as a horizontal plate only (inclined plate approximated to horiz. plate), screening occurs for sources above the bridge plate (diffraction downwards), no reflection at bridge plate | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | as above | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) |
| 7 | embankment | acts as a double barrier, diffraction for direct path (no lateral diffraction), no absorptive/reflective properties, NOTE: The embankment is not considered in the triangulation! | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | as above | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) |
| 8 | ground absorption area | not relevant (generalized ground attenuation) | areas with G=0 assumed to represent water surfaces | yes, freq. dependent using ground factor G (as in ISO 9613-2, section 7.3.1) | empirical ground correction (chart) | freq. dependent using ground factor G (see ISO 9613-2(1996), sect. 7.3.1) | as above | using ground factor G (for favorable and homogeneous) | using ground factor G, averaging with multiple ground absorption areas | yes, using ground factor G (for favorable and homogeneous) |
| 9 | built-up area/foliage | not relevant by default, optionally accord. to VDI 2714 | optionally accord. to ISO 9613-2 | built-up area by sound dispersion (NPM), foliage: via path length with heff | not available | not available | as above | not available | not available in CadnaA (for the time being) | no effect |
| 10 | 3D-reflector | screening based on shortest path difference, two lateral paths, no reflection or by absorption coeff./reflection loss, reflection up to 1st order, no summation of diffraction via multiple edges, no multiple diffraction | see Schall 03 (1990) | not available (due to „effective height“ concept) | see Schall 03 (1990) | not available (due to „effective height“ concept) | as above | see Schall 03 (1990) | not available (just for vertical barriers) | see Schall 03 (1990) |
| 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 Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | as above | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) |
| 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 Schall03 | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) | as above | see Schall 03 (1990) | see Schall 03 (1990) | see Schall 03 (1990) |