HJ
If not stated otherwise, the information applies to HJ 2.4 (2009), HJ 2.4 (2021) and HJ 1358 (2024).
Emission parameter
In CadnaA, the emission parameter shown in the road dialog for a calculation according any of the HJ standards is the mean level Le,7.5m at 7.5 m distance from the road’s axis of an infinite straight road with free sound propagation. This emission parameter is not defined in the HJ calculation standards mentioned above and is used in CadnaA to compare road objects and for direct input. Le,7.5m is calculated for each of the three vehicle types i as follows:
\((L_{e,7.5m})_i=(L_{0E})_i+10 \lg(\frac{N_i}{V_i})+\Delta L_{\text{slope},i}+\Delta L_{\text{road surface}}-16\)
with
- (Le,7.5mE)i: equivalent sound emission level of i-type vehicle per hour, in dB(A)
- (L0E)i: energetic average of the A-weighted sound pressure level i for an i-type vehicle with speed Vi (km/h) at a horizontal distance of 7.5m, in dB(A)
- Ni: average hourly traffic volume of i-type vehicle passing by, for daytime and nighttime, 1/h;
- Vi: average speed of i-type vehicle, km/h
- ΔLslope,i: gradient correction for i-type vehicle, dB
- ΔLroad surface : road surface correction, dB
Emission Level L0E,i
For L0E,i, CadnaA uses the values as specified in JTG B01 (see for example chapter B.2.1.1 of HJ24-2021) and depends on the vehicle category i:
| i | vehicle class | gross vehicle mass | (L0E)i dB(A) |
|---|---|---|---|
| 1 | small | < 3500 kg | (L0E)i=1 = 12.6 + 34.73 log V1 |
| 2 | medium | 3500 - 12000 kg | (L0E)i=2 = 8.8 + 40.48 log V2 |
| 3 | large | > 12000 kg | (L0E)i=3 = 22.0 + 36.32 log V3 |
The equivalent sound pressure level of the total vehicle flow at 7.5 m distance from the road‘s axis results from:
\(L_{e,7.5m}=10 \lg \sum_{i=1}^3 10^{0.1*L_{e,7,5m,i}}\)
User-defined Emission Level L0E,i
If user defined-values for L0E,i need to be specified, it is possible to define the memo variables LOE_S, LOE_M and LOE_L for an individual road object within the memo filed. The suffix S/M/L refer to small, medium and large vehicles.
Note, that the memo variable is written with an „O“ instead of „0“ (zero).
Version of HJ 2.4
The calculations can be performed according to version:
- HJ 2.4 (2009) HJ24-2009
- HJ 2.4 (2021) & HJ 1358 (2024) HJ24-2021 and HJ1358-2024
Calculate outer Lanes separately
By default, the center lines of the outermost lanes of a road are the emission lines. When this option is deactivated just the road’s center line represents the emission line.
Aground spectral (according to GB/T 17247.2)
When using HJ 2.4 (2021) the checkbox can be used to calculate ground attenuation according to GB/T 17247.2 instead of formula A.20 of HJ24-2021. In this case, ground attenuation will be calculated for a frequency of 500 Hz. For further information, see chapter A.3.3 of HJ 2.4 (2021).
When using HJ 1358 (2024) this setting can also be applied instead of formula B.8 of HJ1358-2024, although the standard does not mention such procedure. In this case, it is recommended to deactivate the checkbox. For further information, see chapter B.1.1.6 of HJ 1358 (2024).
2D distance for hm
Barrier attenuation
Attenuation Abar in HJ 1358 (2024)
The approximate calculation as per figure B.3 and table B.4 of HJ 1358 (2024) is not available in CadnaA. Instead, the procedure according to Annex A3 of ISO 9613-2 (1996) (or GB/T 17247.2) can be used when entering the CadnaA object Built-up Area.
However, inputting each building as CadnaA object may be recommendable. In this case, formulas B.10 are used (as done for HJ 2.4). Those formulas are also used when entering screen objects in CadnaA.
No negative path difference
With activated option no barrier attenuation is calculated when the ray from the source to the receiver is above the upper edge of the barrier. HJ 2.4 (2021) is to be calculated with deactivated checkbox, HJ 1358 (2024) is to be calculated with activated checkbox.
Partitioning
Different procedures for partitioning road sources to single point sources are used between HJ 2.4 (2009) and HJ 2.4 (2021) / HJ 1358 (2024).
Calculation of Foliage and Housing
For HJ 2.4 (2021) and HJ 1358 (2024), the calculation of attenuation due to foliage and housing is handled as described in ISO 9613-2 ISO-9613-2-1996 (for foliage, 500 Hz is used). To consider foliage/housing, the respective objects need to be entered, see Built-Up Areas and Foliage.
Housing for HJ 2.4 (2009)
For HJ 2.4 (2009), the calculation of housing is not implemented in CadnaA.