Industry Tab
Information on the calculation options for the following standards or guidelines for industrial sources can be found in the German version of the CadnaA-reference manual:
- VDI 2714/2720
- DIN 18055 (1987)
- OEAL 28 (1987)
- Schall 03 (2014)
The options on tab „Industry“ effect the following types of sources:
- point, line, and area sources, vertical/horizontal (see Common Input Data)
- tennis point of serve (see Tennis - Point-of-Serve)
- parking lot (see Parking Lots)
- optimizable area source (see Optimisable Source)
Table „Propagation Models Industry“
The subsequent table lists the main characteristics of the propagation models for industrial sources as treated in the next 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 | ||||||||
| ISO 9613 (1996) and ISO 9613 (2024) | Nordic Prediction Method (1996) | Nord 2000(using DLL V20) | Ljud fran vindkraftverk | BS 5228 | Harmonoise(using DLL 2.020) | Concawe | NMPB 2008 | CNOSSOS-EU | ||
| 1 | calculation using A-weighted levels | yes | yes (though not part of NPM originally) | yes | yes | yes | yes | yes | yes | yes |
| 2 | spectral calculation | yes, for octaves 63 Hz to 8000 Hz (extended down to 31.5 Hz), for third-octaves 25 Hz to 10000 Hz | yes, for octaves 63 Hz to 8000 Hz | yes (spectrum visible on protocol only) | yes (for A-weighted sum level only) | yes (though not part of original paper) | yes, see ISO 9613 | yes, see ISO 9613 | yes (1/3 octaves, 100 to 5000 Hz) | yes (for octaves 63 Hz to 8000 Hz) |
| 3 | geometrical attenuation (divergence) | full sphere (4π r2) | see ISO 9613 | full sphere (4π r2) | half sphere (2π r2) | divergence mixed with ground attenuation | full sphere (4π r2) | full sphere (4π r2) | point source propagation (4π r2) | point source propagation (4π r2) |
| 4 | attenuation by air absorption | based on air absorption coeff. accord. to ISO 9613-1 (for freq. dependent calculations using the center freq. of each octave resp. 1/3-octave band) | according to NPM, Annex B | yes | using 0.005 dB/m | not available | complex transfer function (via DLL) | based on air absorption coeff. (table) | acc. ISO 9613-1 (for 15°C, 70%) | yes (acc. to ISO 9613-1) |
| 5 | handling of ground reflections | not using image sources, but using an algorithm which includes the correction for ground absorption (see below) | see ISO 9613 | using complex ground impedance | see ISO 9613 | for two categories (soft/hard) | see above | specific algorithm, not by image sources | algorithmic, not by image sources | algorithmic incl. ground absorption (see below) |
| 6 | handling of reflections at obstacles | by image sources up to the 20th order of reflection, reflection condition considers minimum dimension and wavelength at center freq. of octaves or 1/3-octaves, sound power of the image source may include absorption/reflection loss of the reflector | see ISO 9613, but separate criteria for minimum length and height of reflector | yes | not available | see ISO 9613 | see above | see ISO 9613 | yes | yes |
| 7 | attenuation due to ground effect (ground attenuation) | 2 procedures: 1. general method (spectral): using ground factor G (0<=G<=1), 2. alternative method (for A-weighted levels): generalized, not using ground factor G, |
see spectral method of ISO 9613, but with height correction when „significant screening occurs“ | by complex ground impedance (based on entered G value) | two ground categories (over land = soft, over water = hard) | ground attenuation for two categories (soft/hard) and for mixed ground | see above | spectral model only (63 to 4000 Hz, in CadnaA extended to 32 and 8000 Hz) | spectral model (for favorable: ISO 9613-2, for homogeneous specific) | for 2 prop. conditions using ground factor G: - homogeneous cond. - favorable conditions |
| 8 | attenuation due to screening (at objects) | for single and double diffraction based on the path difference of the direct path across the obstacle, screened ray does by default not include a ground attenuation, screening effect considers wavelength REMARK: transm. through obstacles not considered by default, in CadnaA approximative approach using „acoustical Transparency“ |
effective height he is reduced by Δh for single screen, considers wave length, screened ray with ground attenuation | by complex algorithm using Fresnel-zone | not available | see ISO 9613 | see above | using the Fresnel-number based on the path length difference | based on path length difference | single & double diffraction, includes ground effect on both sides of obstacle, with mirror source and receiver |
| 9 | handling of lateral diffraction | by considering two, lateral ray paths (via the vertical edges of an obstacle), lateral diffraction includes the ground attenuation by default | for single screen only | yes | not available | not available | see above | not available | not expressively considered | not considered (for the time being) |
| 10 | handling of multiple obstacles in ray path | using the so called „ribbon band method“ as specified in ISO 9613-2 (2024) also for calculations according to ISO 9613-2 (1996). | at multiple screens: „... find the two most effective single screens.“ (annex C) | yes | not available | not available | see above | so-called „ribbon band method“ is used to obtain path length difference | via path length difference | 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, however not considering any lateral diffraction. | as with multiple screens (no lateral diffraction) | yes | not available | see ISO 9613 | see above | see ISO 9613 | as with multiple screens | see ISO 9613-2 |
| 12 | handling of meteorological effects (wind) | 2 options (empirical correction Cmet): 1. based on the factor C0 2. additionally in CadnaA: derivation of C0 from a distribution of wind direction (which is not treated ISO 9613-2 (1996)), derivation of C0 as described in ISO 9613-2 (2024) not available |
for „moderate downwind or slight temperature inversions“, no meteorol. correction | for a specific meteo. situation (using wind dir. & speed, temp. gradient) | not available | not available | for a specific meteorological situation (using stability class, wind dir. & speed) | for a specific meteorological situation (using stability class, wind dir. & speed) | using occurrences of homogeneous and favorable propagation conditions | using occurrences of homogeneous and favorable prop. conditions, energetic addition |
| 13 | attenuation due to foliage | based on length of the curved ray path (arc of a circle) passing through the foliage (with height h) assuming a radius of 5 km or for ISO 9613-2 (2024) alternatively based on forestal parameters. | based on transmission path length (with Δh) | not available | not available | not available | not available | not available | not available | not available |
| 14 | attenuation due to built-up areas | based on length of the curved ray path (arc of a circle) passing through the foliage (with height h) assuming a radius of 5 km | acc. to NPM, Annex D (internal scattering ΔLi) | not available | not available | not available | not available | not available | not available | not available |
Note
Since for Nord 2000 an external DLL is performing the actual calculations no details are given in the subsequent tables for that standard (see Nord 2000).
Table „Obstacles and Special-Objects“
A further table describes the properties of obstacles and special-objects in CadnaA with each propagation model.
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 | ||||||||
| ISO 9613 (1996) and ISO 9613 (2024) | Nordic Pred. M. (1996) | Nord 2000 (V20) | Ljud vindkra. | BS 5228 | Harmonoise | Concawe | NMPB 2008 | CNOSSOS-EU | ||
| 1 | building | single & multiple diffraction for edges parallel to the ground (shortest path difference), lateral diffraction by vertical edges, not normative: input of transmission coefficient (%), no acoustical transparency by default | diffract. at upper edge, no lateral diffr. (in NPM for single edge only), no acoust. transp. | yes | no effect | diffr. at 1st edge parallel to the ground only, no lateral diffr., no acoust. transpar. | see ISO 9613, but no acoustical transparency, reflection based on airflow resistivity | see ISO 9613 | see ISO 9613 | see ISO 9613, but for homogeneous & favorable conditions |
| 2 | cylinder | single and multiple diffraction via the cylinder based on the shortest path difference, lateral diffraction via the perimeter, reflection up to 1st order (as specified in ISO 9613-2 (2024) also used for calculations according to ISO 9613-2 (1996)) | diffract. at upper edge, lateral diffr. as for a single edge | yes | no effect | see ISO 9613 | see ISO 9613 | see ISO 9613 | see ISO 9613 | for homogeneous & favorable conditions |
| 3 | barrier | single and multiple diffraction for edges parallel to the ground based on the shortest path difference, lateral diffraction via the vertical edges, | diffract. at upper edge, lateral diffr. only at the first vertical edge | yes | no effect | diffr. at 1st edge parallel to the ground only, no lateral diffr. | see ISO 9613, reflection based on airflow resistivity | see ISO 9613 | see ISO 9613 | see ISO 9613, but for homog. & favorable cond. |
| 4 | floating barrier | no diffraction via the lower edge (screening edge without diffraction), otherwise see barrier | see ISO 9613 | yes | no effect | see ISO 9613 | yes | see ISO 9613 | see ISO 9613 | see ISO 9613 |
| 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 | cantilever not available (not compatible with „effective height“ concept) | yes | no effect | see ISO 9613 | yes | see ISO 9613 | not available | see ISO 9613 |
| 6 | bridge plate | diffraction calculation for horizontal plate only (inclined plate approximated to horizontal plate), screening for sources below/above the bridge plate (diffraction up-/downwards), no reflection-induced level increase below the bridge plate (as ground is not modeled by mirror sources) | see ISO 9613 | no effect | no effect | see ISO 9613 | no effect | see ISO 9613 | see ISO 9613 | see ISO 9613 |
| 7 | embankment | acts as a double barrier, diffraction for direct path (without lateral diffraction), no absorptive/reflective properties REMARK: The embankment‘s top edge is not considered in the triangulation of the terrain! |
see ISO 9613 | yes | no effect | see ISO 9613 | yes | see ISO 9613 | see ISO 9613 | see ISO 9613 |
| 8 | ground absorption area | just relevant with the frequency dependent ground attenuation: procedure uses three regions (source, receiver, and middle region), empirical attenuation based on source and receiver height and distance | see ISO 9613 | no effect | no effect | see ISO 9613, also with weighted source data (based on the frequency specified) | based on airflow resistivity (in CadnaA: classes of ground factor G) | see ISO 9613, also with weighted source data (using specified freq.) | using ground factor G (for favorable and homogeneous) | yes, using ground factor G (for favorable and homogeneous) |
| 9 | built-up area/foliage | without screening calculation, attenuation based on the length of the curved ray path (arc of a circle) passing through the built-up area/foliage assuming a radius of 5 km | no built-up area in NPM (in CadnaA as in ISO 9613), foliage: based on path length using heff | no effect | no effect | no effect | no effect | no effect | not available | no effect |
| 10 | 3D-reflector | screening using shortest path length difference, two lateral paths, diffraction can be suppressed for individual edges, n reflection up to 1st order, no summation of diffraction components via multiple edges, no multiple diffraction | no screening effect (not compatible with „effective height“ concept) | no effect | no effect | see ISO 9613 | no effect | see ISO 9613 | see ISO 9613 | see ISO 9613 |
| 11 | self screening | not relevant | not relevant | not relevant | not relevant | not relevant | not relevant | not relevant | see ISO 9613 | see ISO 9613 |
| 12 | additional width/parapet L/R | not relevant | not relevant | not relevant | not relevant | not relevant | not relevant | not relevant | see ISO 9613 | see ISO 9613 |