NMPB-Routes 1996
Calc exactly one Reflection Order
By default, this option is deactivated. In this case, the maximum order of reflection is specified via the „Reflection“ tab (see Reflection Tab).
With this option being activated just 1st order of reflection will be considered. In this case, higher reflections should be accounted for by the multiple reflection correction according to RLS-90 RLS-1990 (see below).
Use Multiple Reflection Correction
When this option is activated the multiple reflection correction is calculated according to RLS-90 (see RLS-90), based on additional input data for each road object. By default, this option is deactivated.
Note
The application of both options, „Calc exactly one Reflection Order“ and „Use Multiple Reflection Correction“, may heavily reduce the calculation time as NMPB-method usually requires a higher order of reflection to be selected to obtain realistic levels.
Extended dialog Road to consider the Correction for Multiple Reflections acc. to RLS-90 (inside red frame)
In this case the dialog is extended at the bottom right by an input scheme to enter the required data (for details see RLS-90, Correction for Multiple Reflections).
Calculate outer Lanes separately
By default, the center lines of the outermost lanes of a road are the emission lines (at a height of 0.5 m). When this option is deactivated just the road’s center line represents the emission line.
Emission Calculation
Three different types of emission spectrum can be selected:
- NMPB - Guide de Bruit:This setting applies the emission spectrum as specified by the original guideline NMPB-1996 (see NMPB-Routes 1996).
- Mithra:This setting applies the modified emission spectrum as used in the former French software MITHRA which differs from the guideline.
- EC-guideline 2003/613/EC:This setting applies the modified emission spectrum (see below) to be used in conjunction with the EC-interim calculation methods VBEB-2003.
Reference Spectrum accord. to 2003/613/EC
The values R(j) of the weighting spectrum to be used in accordance with 2003/613/EC is:
| i | Frequency (Hz) | R(j) in dB(A) |
|---|---|---|
| 1 | 125 | -14,5 |
| 2 | 250 | -10,2 |
| 3 | 500 | -7,2 |
| 4 | 1000 | -3,9 |
| 5 | 2000 | -6,4 |
| 6 | 4000 | -11,4 |
Meteorology
Via the button „Meteorology“ the percentage of „favorable conditions“ in wind sectors stepped by 20° can be specified for the time periods D/E/N separately. The percentage refers to the assessment interval, usually an entire year.
List Box / Locations
For calculations using NMPB 1996 the following items from the list box apply:
- (default): favorable conditions D/E/N = 50/75/100 %
- (favorable): favorable conditions D/E/N = 100/100/100 %
- (homogène): favorable conditions D/E/N = 0/0/0 %
- XXX (1996) with „XXX“ representing a French town and region: data for the percentage of favorable conditions according to NMPB 1996.
Note
The items XXX (2) and XXX (3) do not apply when using NMPB 1996, but refer to NMPB 2008 instead (see NMPB-Routes 2008).
Note
No hint is possible here what percentage may apply to an unknown location when just a general description of the local orography is available.
Note 1 - „Favorable conditions“ are such facilitating the propagation of sound (i.e. which are likely to cause a higher sound pressure level at the receiver point). This situation makes use of the (spectral) ground attenuation for downwind propagation conditions as specified in ISO 9613-2.
Note 2 - The „homogeneous condition“ does not refer to any specific meteorological situation. In fact, the rays are straight lines, not accounting for any atmospheric influence. This kind of meteorological situation has been applied by all former prediction models used in France.
Evening Values = Day Values
With this option active the daytime values will be applied for the Evening period as well.
Additional Information
Diffraction Model
NMPB applies a different correction with one screen and with two screens. The correction of ground attenuation for rays above barriers depends on the distance from the source to the first barrier, and from the distance from the last barrier to the receiver. Thus, the obtained results are specific to the NMPB-approach and not due to CadnaA-implementation (see equation (16) in chapter 7.4.4 of NMPB NMPB-1996).
Additional Road Surfaces
The additional road surfaces selectable according to EC-guideline 2003/613/EC are selectable from the Road dialog, list box “Road Surface“.
see NMPB-Routes 1996
Meteorological Situations
The table provides information on combinations of wind speed Ui and temperature Ti corresponding to specific propagation types. The original data is from LRPC of Angers (Laboratoire Régional des Ponts et Chaussées, Angers/France).
In this table, 5 propagation types have been defined:
| - - | very high attenuation due to very rising rays (“Unfavourable” situation) |
|---|---|
| - | high attenuation due to rising rays (“Unfavourable” situation) |
| Z | null meteorological effects due to linear rays (“Homogeneous” situation) |
| + | moderated increase of noise level due to going down rays (“Favourable” situation) |
| + + | high increase of noise level due to going down rays (“Favourable” situation) |
Impossible meteorological situations are marked by grey cells.
The input conditions (Ui; Ti) of the grid fit to the following criteria:
| U1 | strong wind (3 to 5 m/s) contrary to the emitter – receptor sense |
|---|---|
| U2 | from light to mean adverse wind (1 to 3 m/s) |
| U3 | no wind or traverse wind |
| U4 | from light to mean carried wind |
| U5 | strong carried wind |
and
| T1 | day; strong radiation; dry surface; not much wind |
|---|---|
| T2 | conditions identical to T1 but one at least is not verified |
| T3 | rising or setting down of sun or (windy and cloudy weather; surface not so wet) |
| T4 | night and (cloudy or windy) |
| T5 | night and clear sky and light wind |