Civil Engineering Reference
In-Depth Information
1000
800
Re Z
600
400
200
0
−
200
Im Z
−
400
−
600
−
800
−
1000
0
0.5
1
1.5
2
2.5
3
3.5
4
Frequency (kHz)
Figure 2.9
The impedance
Z
at normal incidence of a layer of fibrous material of thick-
=
10 000 N m
−
4
s, with an air gap of thickness
ness
d
=
10 cm, and flow resistivity
σ
d
=
10 cm.
1
0.8
0.6
0.4
0.2
no gap
gap
0
0
0.5
1
1.5
2
2.5
3
3.5
4
Frequency (kHz)
Figure 2.10
The absorption coefficient for the two previous configurations.
