NMPB-Routes 1996

Emission Parameter

The emission parameter in NMPB-1996 („Nouvelle Méthode de Prévision du Bruit“) is the A-weighted sound power level per octave band L_Aw,i of a point-like sub-source S_i in dB(A) NMPB-1996. This level calculates from:

\(L_{Aw,i}=10 \lg (10^{(E_{VL}+10 \lg Q_{VL})}+10^{(E_{PL}+10 \lg Q_{PL})})+20 dB+10 \lg l_i+R(i)\)

with

E_VL: sound power level of the light vehicles, in dB(A)
Q_VL: traffic number of the light vehicles (max. mass m < 3500 kg), in veh/h
E_PL: sound power level of the heavy vehicles, in dB(A)
Q_PL: traffic number of the heavy vehicles (max. mass m >= 3500 kg), in veh/h
l_i: length of the sub-source S_i, in m
R(i): octave values of the reference spectrum for road noise, in dB(A)
i: running number of octave

In CadnaA, the overall traffic flow Q (in vehicles/hour) and the percentage of heavy vehicles p% is to be specified instead. The relation between those figures and the ones above are:

\(Q=Q_{VL}+Q_{PL}\) and \(p\%=\frac{Q_{PL}}{Q}\)

Dialog Road (for NMPB 96)

Emission Parameter LwA’

The emission parameter displayed on the dialog Road is A-weighted total sound power level per unit length L’_Aw,i in dB(A) according to the modified equation:

\(L'_{Aw,i}=10 \lg (10^{(E_{VL}+10 \lg Q_{VL})/10}+10^{(E_{PL}+10 \lg Q_{PL})/10})+20dB+\psi\:\text{dB(A)}\)

Note

This value includes the correction for the vehicle type, the type of traffic flow, the correction of road gradient and the road surface correction ψ (see below).

Reference Spectrum

The values R(i) of the weighting spectrum are listed in the following table:

i	Frequency(Hz)	R(i) in dB(A)
1	125	-14
2	250	-10
3	500	-7
4	1000	-4
5	2000	-7
6	4000	-12

Emission Level E

The emission level E is taken from the following diagram:

Diagram for NMPB-specific emission parameter E (approximative)

Legend (road gradient g%):

	Horizontal (-2% < g < 2%)	Monté (g > 2%)	Descente (g < -2%)
Fluide continu	1.1	1.2	1.3
Pulsé non différencié	2.1	2.2	2.3
Accéléré	3.1	3.2	3.3
Décéléré	4.1	4.2	4.3

This diagram considers:

two types of vehicles (light and heavy)
four types of traffic flows (fluide continu, pulsé non différencié, accéléré, décéléré),
three types of road gradient (horizontal, montée, descente) and
the traffic speed for light and heavy vehicles.

MDTD

The „Mean Daily Traffic Density“ (MDTD, vehicles/24h) does not exist in NMPB as an input parameter for traffic data. Nevertheless, this feature is provided by CadnaA applying the road types of the German road noise standard RLS-90 12354-1999 in conjunction with VBUS VBUS-2006. The respective data for the hourly traffic data M (veh/h) and the truck proportion p (%) is given in the next table.

Attribute Value STRGATTNR	Road Type	Day (6-18 h)		Evening (18-22 h)		Night (22-6 h)
Attribute Value STRGATTNR	Road Type	Q (veh/h)	p (%)	Q (veh/h)	p (%)	Q (veh/h)	p (%)
0	Motorway	0.062 * MDTD	25	0.042 * MDTD	35	0.014 * MDTD	45
1	Federal Road	0.062 * MDTD	20	0.042 * MDTD	20	0.011 * MDTD	20
2	Ordinary Road	0.062 * MDTD	20	0.042 * MDTD	15	0.008 * MDTD	10
3	Local Road	0.062 * MDTD	10	0.042 * MDTD	6.5	0.011 * MDTD	3

Source Geometry

The height entered in the dialog Geometry is the height of the road’s surface. The source height is 0.5 m above the road’s center line or above of the center lines of the outer lanes.

Speed Limit (km/h)

The minimum speed according to NMPB is 20 km/h for all types of vehicles. The maximum speeds are 140 km/h for autos and 100 km/h for trucks. For higher speeds a speed of 140 km/h for autos and of 100 km/for trucks is used. In case a speed below 20 km/h is entered, 20 km/h is applied instead.

Road Surface

With NMPB, the correction for different road surfaces is already included in the emission level E. By default, the road surfaces listed in the following table are available (types „EC“ resulting from VBEB-2003).

Note

The selected road surface influences the spectrum when LAw' is entered directly.

Attribute Value STRONR	Road Surface	Spectrum Type applied	road surface correction ψ in dB at a speed of
Attribute Value STRONR	Road Surface	Spectrum Type applied	<= 60 km/h	<= 100 km/hEC: <= 80 km/h	<= 130 km/h
1	Enrobé bitumé	1	0
2	Enrobé drainant	2	0	0-3,5 *)	3,5
3	Chaussée cloutée	1	2
4	Béton lisse	1	0
5	Béton strié	1	3
6	Pavés (en ville)	1	3
101	EC: Porous surface	1	-1	-2	-3
102	EC: Smooth asphalt	1	0
103	EC: Cement concrete	1	2
104	EC: Smooth texture Paving	1	3
105	EC: Rough texture Paving	1	6

spectrum type 1: road spectrum (see previous section „Reference Spectrum“)
spectrum type 2: spectrum for „Enrobé drainant“ (see below)

* correction linearly increasing from 0 dB for 50 to 3,5 dB for 100 km/h

Spectrum for road surface „Enrobé drainant“ (for ψ = 3,5 dB(A)):

i	Frequency (Hz)	R(j) in dB(A)
1	125	0
2	250	0
3	500	0,5
4	1000	5,5
5	2000	7
6	4000	7

User-defined Road Surfaces

With NMPB selected, additional road surfaces can be defined by the user. Open the local library for sound reduction indices (menu Tables|Libraries (local)|Sound Reduction Indices) and enter a new line via the table’s context menu. For a sound reduction index spectrum to be selectable as a road surface correction, the ID has to start with the text sequence: NMPB_X, where X is an integer without a leading zero (for example: NMPB_1, NMPB_11, NMPB_111, but not NMPB_01). The entered name will be shown at the end of the default list of road surfaces.

Example: user-defined road surface spectrum

Traffic Flow

The selected type of traffic flow applies to all daily periods D/E/N. Available types are:

fluide continu
pulsé non différencié
accéléré
décéléré

Button DEN

Clicking this button in line „Traffic Flow“ enables to define different types of traffic flow for the time periods Day|Evening|Night.

Note

The following object attributes are available: FLOWNRD/E/N (read/write), FLOWD/E/N (read only, for details see Table Object Attributes in the manual „Attributes, Variables and Keywords“).

Gradient (%)

The road gradient can be entered in % or be calculated automatically, depending on the z-heights of the road.

For information on the different options offered in the list box „Road Gradient“ of the dialog Road see Common Input Data, Road Gradient (%), for details.

Correction for Multiple Reflections

There is no global correction available in NMPB-96 to correct for multiple reflections. However, CadnaA enables to restrict the calculation using image sources to the 1st order of reflection and to correct for multiple reflections according to RLS-90 RLS-1990.

see NMPB-Routes 1996 and RLS-90