Civil Engineering Reference
In-Depth Information
1
0.9
Test
FEM
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0.1
0
100
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Frequency(Hz)
Figure 13.21
Passive absorption of the foam (LeRoy 2008).
BEM reception
Trim FEM
Air gap mesh
between the
structure and the
baffic
Foam/Felt
+
Binappe carpet
Fully trimmed vibro-
acoustic response
Structure FEM
Cavity FEM
Felt + Carpet
structure steel
Foam spacers
Trim FEM
mock-up
Bem cmission
Diffuse field excitation
(a) (b)
Figure 13.22
Example of the modelling of a fully trimmed car floor panel: (a) radiation
problem, the floor panel is mechanically excited and radiates in a cavity; (b) transmission
loss problem (Duval
et al
. 2008).
of the panel structure and the acoustic power radiated by the structure in the receiving
media. This approach allows for incompatible meshes and authorizes the solution of large
systems such as a fully trimmed vehicle (Anciant
et al
. 2006).
The examples of two types of floor insulator are shown here: (i) an absorption type,
called bi-permeable concept, with an airflow resistive carpet superposed on a two-layer
system made up from a soft spring felt on top of foam spacers; and (ii) an insulation type,
with a 2 kg/m
2
heavy layer inserted between the airflow resistive carpet and the soft felt
spring - foam spacer system. A graphic description of the meshed components is given
in Figure 13.22. Figure 13.22a describes the radiation configuration while Figure 13.22b
