Built-Up Areas and Foliage
Built-Up Areas
Built-up areas are defined by a closed polygon and by its height (on dialog Geometry). The resulting attenuation due to built-up areas depends on the guideline selected for the respective type of source. With calculation according to e.g. VDI 2714 or ISO 9613-2 the attenuation due to built-up areas is taken into account for areas as defined. When calculating traffic noise with the setting „strictly according to RLS-90“ or „strictly according to Schall03“, however, no attenuation occurs with built-up areas (tabs Road“ and „Railroad“ on dialog Calculation|Configuration).
Dialog Built-Up Area
Calculation according to VDI 2714
According to VDI-guideline 2714, section 6.4.2, the attenuation by built-up areas DG for single sources and for propagation through scattered buildings (i.e. no extending building facades):
\(D_G=(m*B*s_G-D_{BM})dB\geq0dB\)
with
- m: average reciprocal length of edges in 1/m
- B: area coverage (of buildings) in %
- sG: length of sound path through the built-up area in m (for this reason the height of the object „Built-Up Area“ is relevant)
- DBM: attenuation due ground & meteorology in dB
With single buildings the average reciprocal length of edges is 0.1 m-1 at maximum. With scattered halls smaller values for m apply.
The length of sound ray sG through the built-up area is evaluated for a curve radius of 5000 m from source to receiver. Enter the average height of buildings with the area in dialog Built-Up Area|Geometry. According to VDI-guideline 2714 the sum DBM+DD+DG is limited to a maximum value of 15 dB (DD: attenuation due to foliage).
The application of the object Built-Up Area is useful where the geometry of individual objects is not available. Otherwise, the object Building should be used.
Calculation according to ISO 9613-2 (1996) and ISO 9613-2 (2024)
According to ISO 9613-2 (1996) annex A.3 and ISO 9613-2 (2024) annex A.4, the attenuation due to housing AHous,1 results from:
\(A_{hous,1}=0.1*B*d_B\:dB\)
with:
- B: area coverage in % \(=(\frac{\text{total building area}}{\text{total area}})\)
- dB: length of sound path through the built-up area in m
The attenuation due to housing AHous,1 is limited to 10 dB according to ISO 9613-2. The sum of attenuations Agr+Afol+Ahous, however, is not limited to 15 dB - compared with VDI 2714. Using a text block with the name OLD_OPT_CALC this limitation can be engaged (text to be entered: iso_asum_15db_x125=1).
Note
The contribution of AHous,2 according to ISO 9613-2, is not considered by CadnaA.
Foliage
Dense woods („foliage“) are defined by a closed polygon and by its height (on dialog Geometry). The resulting attenuation due to foliage depends on the guideline selected. In the following, the procedures according to VDI 2714, ISO 9613-2, and Schall 03 (1990) are explained.
Calculation according to VDI 2714
According to VDI-guideline 2714, section 6.4.2, the attenuation due to foliage DD calculates from:
for A-weighted levels: \(D_D=0.05\:dB/m*s_D\)
for spectra: \(D_D=[0.006(\frac{f}{Hz})^{1/3}]\:dB/m*s_D\)
with sD: length of sound path through the foliage in m.
The length of sound ray sD through the foliage is evaluated for a curve radius of 5000 m from source to receiver. Enter the average height of buildings with the area in dialog Foliage|Geometry. The resulting attenuation just holds for permanent (leaves!) and dense woods (i.e. with dense undergrowth).
According to VDI-guideline 2714 the sum DBM+DD+DG is limited to a maximum value of 15 dB (DG: attenuation by built-up areas).
Calculation according to ISO 9613-2 (1996) and ISO 9613-2 (2024) simplified method
According to ISO 9613-2 (1996) annex A.2 and ISO 9613-2 (2024) annex A.2.2 (simplified method), attenuation due to foliage calculates from:
\(A_{fol}=D_f*d_f\)
with
- df: length of sound path through the foliage in m.
- Df: attenuation as shown in the next table:
| path lengthdf (m) | octave band center frequency (Hz) | 63 | 125 | 250 | 500 | 1k | 2k | 4k | 8k |
|---|---|---|---|---|---|---|---|---|---|
| 10 <= df <= 20 | attenuation (dB) | 0 | 0 | 1 | 1 | 1 | 1 | 2 | 3 |
| 20 <= df <= 200 | attenuation (dB/m) | 0,02 | 0,03 | 0,04 | 0,05 | 0,06 | 0,08 | 0,09 | 0,12 |
Note
The attenuation by built-up areas DG is not limited by ISO 9613-2.
Calculation according to ISO 9613-2 (2024) detailed method
ISO 9613-2 (2024) annex A.2.3 describes the attenuation based on forestal parameters.
Dialog Foliage
To use the detailed method according to annex A.2.3, the corresponding option must also be activated in the calculation configuration (see ISO 9613 (2024)). The entries from Table A.6 of ISO 9613-2 (2024) can be selected via dropdown, the entry "(default)" corresponds to "Normal forest". With "(user-defined)" you can use your own values for the forestal parameters, with "(input spectrum)" the spectrum for the attenuation can be entered directly.
Note
The use of attenuation based on forest parameters is possible exclusively for calculations according to ISO 9613-2 (2024).
Calculation according to Schall03 (1990)
The procedure corresponds with the calculation in guideline VDI 2714 for A-weighted levels.
When performing road noise calculation with setting „strictly according to RLS-90“ no attenuation due to foliage is considered.
Calculation according to Schall03 (2014)
The attenuation due to foliage is not considered (see section 6.1 in 16BImSchV-2014).