1. No category

Noise from roads, what
data is needed and how
to determine noise levels
Foto by Dragan Cekic
Presentation Training G2G
Servie, Belgrade November 30
Jan Jabben
National Institute for Public Health
and Environment (RIVM)
The Netherladns
1
Belgrade November 30
Basic model I: Single source
a
I=
W
⋅ µ air ⋅ µ soil ⋅ (µbarrier )
2
2πa
Take Lp = 10log(I) gives basic formula:
Lp = LW − 8 − 20 log(a ) − Aair − Aground (− Abarrier )
Sound Power Level
Attenuation air/ground
LW = 10log(W) in dB(A)
Attenuation with distance
Soft ground (grass, loose turf): Aground ≅ 3 dB
Hard ground (concrete, water): Aground ≅ 0 dB
2
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Some Typical sound power levels Lw in dB(A)
Boeing 737/300 take off
B737/300 landing
Train of 250 m length 140 km/h
Truck on a highway 90 km/h
141
136
135
111
105
Passenger car at a highway 100 km/h
Vacuum cleaner
Average speaking voice
3
86
71
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Excercise basic model I (single source)
Suppose an industrial source has a sound power Lw = 120 dB(A)
The facade of a dwelling is at 200 m distance
Propagation is over grass
Assume air absorption is 0.005 dB per m; no barriers
Question: what the level Lp at the facade ?
Question: Is this level annoying for the inhabitants?
Solution
Lp = Lw- 8- 20log(a) – Aair - Aground
= 120 – 8 – 20log(100)- 1 – 3 = 68 dB(A)
Which is annoying. At 20 dB insulation, the indoor level would be
continuously at 48 dB
4
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Basic model II: Multiple sources in line
a
W
⋅ µ air ⋅ µ soil ⋅ (µ barrier )
I=
2as
0 < µ air < 1 Reduction factor air absorption
s
Take Lp = 10log(I) gives basic formula:
W = average acoustic
power of vehicles
s = average spacing of
vehicles
a = distance to receiver
Lp = LE − 10 log( a ) − Aair − Aground (− Abarrier )
Emission LE= 10log(W/2s) = Lw-10log(2s)
Soft ground (grass, loose turf): Aground ≅ 3 dB
Hard ground (concrete, water): Aground ≅ 0 dB
5
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Some Typical Emission LE for line sources
94
Airport take off route with 20 planes/hr
Motorway 6000 cars/h at 100 km/u
93
Railway line with 6 trains/hr at 140 km/h
Municipal road with 500 cars/hr 50 km/h
6
88
73
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Excercise basic model II (road traffic)
● In stead of industrial source now at 100 m a two lane road is present
● each hour Q=2 x 300=600 passenger cars are passing by, with speed
V~50 km/h
● Lw depends on speed Lw ~45+30log(V) = 96 dB(A)
● Emission LE depends on speed and number/h, s=1000*V/Q=83 m;
● Assume air and ground att as previous: 4 dB
● What is the level at the same dwelling, is this annoying
● What would be the level at 20 m ? for a road with 1200 cars/h
● LE ≅ Lw-10log(2*83) =96+10log(166) = 74 dB
● Lp=LE-10log(a)-Aair-Aground = 74-20-4 = 50 dB, in general that is
considered a good acoustic quality
● At 20 m with double traffic volume, the level increases with
10log(100/20)+10log(2)=10 dB, so Lp would be 60 dB which can
be considered as a moderate acoustic quality
7
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Attenuation by barriers or objects
Road traffic:
Att~10log(3+40δ)
8
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Finite road segments
θ
1
If only part of the road is visible, a correction Cvision=10log(θ/180)
Can be applied. Suppose θ=90 degrees, what is the correction ?
9
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Downwind and upwind condition
Source J.S. Lamancusa Penn State
7/30/2009
• Measurements should
always be conducted in
downwind conditions
source
Models work well
Models don’t work well, level are
much lower than standard calculation
• Considerable part of the time levels are lower than with
downwind calculation, to account for this, in addition to air and
ground attenuation, a meteo correction Cmeteo is substracted
• Close to the source Cmeteo ~ 0 dB
• More than 100 m Cmeteo ~ 2-5 dB
10
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Model accuracy
required
overcomplex
Somewhere here its good enough
Usually ± 2 dB up to 100m is feasible
11
Model complexity
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Calculation Models for road traffic noise
There are many, many models for an extensive list e.g. see
http://www.woelfel.de/en/products/modelling-software/immi-guidelines.html
Some most well known are:
● French NMPB routes 1996 (Interim method)
● Harmonoise (still not accepted, some ms consider it overcomplex..)
● Dutch standard calculation methods (SCM) 1 and 2
● To be edited CNOSSOS (Common Noise Assessment Methods)
Models differ in the definition, of vehicle categories, emissions,
attenuation from ground, air, barriers, meteo correction etc
But all models have in common:
● Leq = E - Σ A (broadband or per octave band)
● data on traffic volumes and speeds per category are needed for
all roads causing Lden/Lnight >55/45 within agglomerations
and major roads with more than 6 milion vehiclse/yr
Averaged over day (7-19), evening (19-23 and night time (23-7)
12
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
13
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
A calculation example with Dutch SCM1
Group 1 бапканска
• Measure Leq, 10 min,
• Count light, medium,
heavy vehicles
1
a
2
b
Group 2 Terazije
• Measure Leq, 10 min,
• Count number light,
medium, heavy vehicles
• estimate a
14
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
First Guess Dutch SCM 1 method
receiver height [m]
height of road [m]
ground distance road-receiver
[m]
soil type 0=hard 1=soft
fraction of housing other side
Light vehicles
middle weight trucks
heavy trucks
motorbikes
LAeq in dB(A)
бапканска
1.5
0
20
0
0
Terazije
1.5
0
20
0
0.5
number/hr
number/hr
150
2
0
0
1000
50
40
0
55
65
END: averages for Day (7-19) Evening (19-23u) Night (23-7)
are needed Next session we will try to validate our first guess
15
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Mapping road traffic noise
● We used basic models for a calculation on a single points and for a
single source (only one road or point source)
● To obtain noise maps, the calculation is needed on many points, for
example on points on a lattice (grid) of 10 x 10 m (recommended by EC
good practicing guide)
● Also in practice, many road segments/buildings and different ground
types affect the noise levels
● apart from method, maps require software to take all this into account
Most important data (preferably in GIS):
1 Digital Road network, containing traffic data
on its segments (number/hr day, evening,
night and speeds)
2 Digitized data of buildings and heights
(if possible terrain data: hard or soft soil)
16
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Excercise
● Suppose a road has 600 vehicles/hr and cause LAeq of 60 dB on a
nearby dwelling
● What will be the level if traffic increases to 700 vehicles/hr ?
● Increase of LAeq will be + 10log(700/600) = 0,7 dB(A)
This is small compared to model accuracy ± 2 dB(A)
Statistics of many roads also helps to limit errors in determining the
number of exposed dwellings
17
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Traffic counts (most accurate)
18
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Traffic counts beware of periodicy
% of total number 0-24u
passenger
10
9
8
7
6
5
4
3
2
1
0
0
19
trucks
6
12
18
24
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
hour
0
1
2
3
4
5
6
7
8
9
 10
11
12
13
14
15
16
17
18
19
20
21
22
23
20
% of total 0-24
passenger
trucks
1.1
0.8
0.4
0.3
0.5
1.5
4.8
6.7
6.2
5.5
5.3
5.3
5.5
5.7
5.9
6.6
7.2
6.9
6.5
5.6
4.2
3.3
2.4
1.8
0.3
0.4
0.4
0.6
0.8
2
4.8
7.5
9
8.7
9
9
7.5
8.4
7.8
6.9
5.4
4
2.7
1.8
1.2
0.9
0.6
0.3
Av day 7-19
6.1
7.2
Av evening 19-23
3.9
1.1
Av night 23-7
1.4
1.2
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Suppose counting is done 15 min. between 10 and 11 hour result
150 passenger cars and 10 trucks
What will be average number/hr for day Evening and night ?
Passenger cars
Day 600 *6.1/5.3= 690 pass cars
Evening 600* 3.9/5.3= 440 cars
Night 600*1.4/5.3= 160 cars
Trucks
Day 40 *7.2/9= 32 cars/hr
Evening 40* 1.1/9= 5 cars/hr
Night 40*1.2/9= 5 cars/hr
21
10-11 h
5.3%
9%
Av day 7-19
6.1%
7.2%
Av evening 19-23
3.9%
1.1%
Av night 23-7
1.4%
1.2%
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Sensitivity of traffic data
● Not all roads have to by incorporated, only major roads > 6 miln
vehicles/year and within agglomerations roads that cause Lden>55
dB or Lnight > 45 dB
● In practice for a major city, this means almost all roads…
● But often detailed information on how many cars on a road pass by
is not available
● In that case an estimation can be made based on the type of road
● This can give fairly good results, as long as a road network is
available en sufficiently complete
● In detail traffic estimation methods are described in ‘Good Practice
Guide for Strategic Noise Mapping’
http://ec.europa.eu/environment/noise/pdf/wg_aen.pdf
● Noise levels are relatively little sensitive for errors in traffic data
22
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
From ‘Guide for Strategic
Noise Mapping’
http://ec.europa.eu/environ
ment/noise/pdf/wg_aen.pdf
23
RIVM, Jan Jabben, Noise workshop Belgrade, November 30
Counting exposed dwellings
● Different options:
- Calculate Lden/Lnight on points at exposed facade of all dwellings
(expensive)
- Or use grids (GIS) with sufficiently small gridsize (~10 x 10 m) and
combine these with grids containing density of population (relatively
less laborious)
Further to be discussed next training
24
RIVM, Jan Jabben, Noise workshop Belgrade, November 30