CRN
Use Non-Standard Reference Time
When the option „Use Non-Standard Reference Time“ is activated the time intervals and penalties on the „Reference Time“ tab are taken into account in the calculation.
Railway noise - according to the majority of standards/guidelines - is calculated just for two daily periods: day and night. When doing calculations with respect to END (Environmental Noise Directive EU2002/49/EG-2002), however, this option has to be activated to consider the number of trains (or the emission parameter) during the Evening period as well.
see also:
Note
The values displayed on the „Reference Time“ tab (D/E/N=12/4/8 h) will be updated based on the defined time intervals (hours Day/Evening/Night).
Reflection via Correction (1.5 dB), NOT via mirror sources
CRN clause 31.2 CRN-1995 specifies that the reflection from buildings or other reflecting objects (e.g. barriers) on the opposite side of the road have to be considered by a correction of 1.5 dB depending on the angle of the reflecting object/s seen from the receiver. The value of 1.5 dB occurs in case the entire length of the road has reflecting buildings (i.e. is the maximum reflection correction).
For more details and examples see CRTN, Reflection via Correction (1.5 dB), NOT via mirror sources.
Additional Information
Facade Effect
CRN specifies in clause 31.1 that for calculations of the noise level at a distance of 1 metre in front of a façade a correction of +2.5 dB has to be made. CadnaA does not apply this correction automatically for the time being as this CRN-specification do not match the normal approach when calculating façade reflections.
for more details and examples see CRTN, Facade Effect
Screening Effect
In CRN, negative path differences cause screening (see chart 6a in CRN-1995). This means that a substantial screening correction may result with small path differences z (0<z<0.4 m) in situations where the ray is not intersecting with an obstacle, but just passing above its top edge („illuminated zone“).