Civil Engineering Reference
In-Depth Information
loss factor is frequency independent, the impact sound pressure level
L
n
in the receiving
room (see section
6.2.2
), will be frequency independent.
calculate the normalized impact sound pressure level giving
⎛
⎞
f
c
L
≈⋅
10 lg
+
82 dB.
(6.74)
⎜
⎟
n
⎜
⎟
2
m
η
⎝
⎠
Measurements of the loss factor in practice have shown that it is slightly frequency
dependent. Following Craik (1996), we may, as a rough estimate for heavy floors of
concrete etc., write
1
η=+
0.015.
(6.75)
f
80
70
60
50
140 mm concrete
Calculated
260 mm hollow concrete
40
30
20
260 mm hollow concrete
10
0
63
125
250 500 1000 2000 4000
Frequency (Hz)
Figure 6.20
Normalized impact sound pressure level of a 140 mm thick concrete slab and a 260 mm thick
hollow core concrete slab. Laboratory measurement data together with calculated results for the concrete slab.
An example is given in
Figure 6.20
showing results of laboratory measurements on
a concrete slab of thickness 140 mm. Comparing with calculated results we have used
of the slab is 320 kg/m
2
and the critical frequency is 120 Hz. As seen from the figure
