Civil Engineering Reference
In-Depth Information
1
2
⎡
⎤
⎢
⎥
(
)
E
1
−
υ
1
2
K
2
2
c
f
=
⎢
⎥
where
K
=
.
(8.39)
dil
c
(
)(
)
ρ
h
2
π
⎛
⎞
1
−
2
υ
1 υ
+
⎢
⎥
22
2
2
hh
ρ
+
⎜
⎟
211
⎢
⎥
6
⎝
⎠
⎣
⎦
80
Measured R'
Pred. E=5.0 MPa
Pred. E=6.0 MPa
Mass law
70
60
50
40
30
20
10
0
63
125 250 500 1000 2000 4000
Frequency (Hz)
Figure 8.24
Sound reduction index of sandwich panel of 13 mm plasterboards and 55 mm polyurethane core.
Predicted data using two different modulus of elasticity for the core. Measured data from Homb et al. (1983).
Table 8.2
Material data for sandwich panel in
Figure 8.24.
E-modulus
(Mpa)
Density
(kg/m
3
)
Loss factor
Poisson's
number
Face
sheets,
13
mm
3200
800
0.05
0.30
plasterboard
Core, 55 mm polyurethane
5 − 6
50
0.05
0.35
Concerning the fit between predicted and measured results in the lower frequency
range, one should be reminded that the prediction applies to an infinite size panel, i.e. no
area effect is included. Furthermore, the panel area of 7.5 m
2
being used for the
