1. Workpackage “Noise Modelling”
Sound Propagation -
new propagation models
Dietrich Heimann
(translated and presented by U. Isermann)
DLR - Institute of Atmospheric Physics (IPA)
Oberpfaffenhofen

2. Workpackage “Noise Modelling”
emission
perception
transmission
immission

3. Workpackage “Noise Modelling / Propagation”
1. Propagation effects
2. Propagation models
3. The IPA approach

4. Propagation effects inhomogenous, turbulent atmosphere absorption
reflection
refraction
scattering
diffraction
topography,
buildings, obstacles

5.   Propagation effects altitude lateral distance from baseline shadow
for a
temperature decrease temperature increase
with altitude with altitude
or for
 wind 
upward refraction downward refraction  
shadow
single reflection
multiple reflection
lateral distance from baseline

6. Propagation effects shadow zone due to refraction
source
contibutions from
direct and
reflected sound
contributions from
diffraction
scatterering
shadow zone due to refraction
shadow zone due to topography
source
contributions from
direct and
reflected sound
contributions
from diffraction
scattering

7. Magnitude of propagation effects:
Spherical wave attenuation:  Lmax - 6 dB per doubling of distance
Additional effects:
Atmospheric absorption:  - 1 dB je 100 m (1000 Hz)
 - 5 dB je 100 m (4000 Hz)
Ground effects:  - 10 dB for grazing incidence
Refraction:  - 25 dB for upward refraction
 + 6 dB for downward refraction
Scattering, diffraction  -25 dB attenuation limit
in shadow zones

8. Workpackage “Noise Modelling / Propagation”
1. Propagation effects
2. Propagation models
3. The IPA approach

9. Sound propagation models
1. Standard models (z.B. ISO 9613, AIR 1845, Doc.29)
Geometric term + different correction factors
Atmospheric effects not accounted for
(or only by simplifying approaches)
2. Numerical models (e.g. Euler model)
The more effects, the more accurate the model-
but with increasing modelling and calculation efforts!

10. Sound propagation models
Euler model:
Example: barrier of trees  wind field  sound propagation

11. Sound propagation models
Euler model:
Airport environment as a field of application ?

12. Sound propagation models
Euler model:
Applied for direct airport environment (1051) km3
and a frequency of 1000 Hz:
Mesh-width of calculation grid: 3,4 cm
Number of meshs: 1,2  1015
Numerical time step needed: 100 s
Number of time steps: 300,000
Calculation time (NEC SX4) per mesh and step: 1 s

13. Sound propagation models
Euler model:
Applied for direct airport environment (1051) km3
and a frequency of 1000 Hz:
Mesh-width of calculation grid: 3,4 cm
Number of meshs: 1,2  = 144 PByte
Numerical time step needed: 100 s
Number of time steps: 300,000
Calculation time (NEC SX4) per mesh and step: 1 s
Total calculation time: 360 Ts = 11 million years

14. Sound propagation models
Calculation
time:
2030:
24 h ?????
2036:
15 min ????
Present: Process studies
Future: Standard procedure ?

15. Workpackage “Noise Modelling / Propagation”
1. Propagation effects
2. Propagation models
3. The IPA approach

16. The IPA approach Goal: Numerical models ... ... develop them
... use them as a reference
Derive simplified models to
- increase the accuracy of
standard procedures
- but maintain their practicability
and usability

17. The Lagrange model (sound particles)
The IPA approach
The Lagrange model (sound particles)
Hz up to 5000 m propagation distance
source altitude: m
wind at 1600 m: m/s
ground wind
wind at 1600 m

18. The IPA approach Realisation: Advantage:
Use the principle of the standard approach:
Calculate the excess attenuation LMB due to meteorological and ground effects using the Lagrange model.
Store the values of LMB for a set of different propagation situations in attenuation lookup tables.
Advantage:
Only moderate increases in computation time are needed.
This approach can also be used for standard models.

19. Independent parameters:
The IPA approach
Independent parameters:
7 classes of source altitude
8 classes of ground receiver distance
6 classes of wind speed (10 m above ground)
12 classes of angle between wind direction
and direction of propagation
3 atmospheric stability classes
8 frequency classes (octave bands)
 64,512 possible combinations ….

20. The IPA approach
Example 1: source: 1600 m, wind: 10 m/s, atmosphere: neutral
quieter
-18 dB
0 dB
+9 dB
louder

21. The IPA approach
Example 2: source: 50 m, no wind, atmosphere: unstable
quieter
-18 dB
0 dB
+9 dB
louder

22. The IPA approach Example 3: source: 100 m, wind: 2 m/s, inversion
quieter
-18 dB
0 dB
+9 dB
louder

23. Workpackage “Noise Modelling / Propagation”
Summary:
 Progress in the development of complex
sound propagation models
 Derivation of a simplified model
 Definition of pre-calculated tables for
meteorology- and ground-excess attenuation which can also be used for standard models

24. Workpackage “Noise Modelling / Propagation”
Validation ...
... based on 1 year noise monitoring at Munich airport (2003)
 6 aircraft types, monitored noise values (FMG)
 radar information on aircraft position (DFS)
 meteorological information (DWD, Uni München, FMG)
noise
meteo