Civil Engineering Reference
In-Depth Information
for direct transmission through the 50 mm concrete slab, which has a critical frequency
of about 400 Hz.
80
70
60
50
40
30
2 x 13 mm plasterboard
20
Concrete slab
Elastic layer
Primary floor
10
0
63
125 250 500 1000 2000 4000
Frequency (Hz)
Figure 9.16
Standardized level difference between two rooms for music practice. Effect of flanking
transmission by way of a floating concrete slab.
9.3.1
Flanking sound reduction index
As an example on the calculation of the apparent sound reduction index, where the
flanking transmission is included, we shall assume that only flanking paths of the type
indicated by “Ff” on
Figure 9.15
are contributing. To make use of the flanking reduction
index we shall have to express it by relevant and measurable quantities applied to the
flanking elements involved. We then have a situation as sketched in
Figure 9.17
, where
there is a direct transmission through the partition of area
S
S
and reduction index
R
d
together with a transmission path of the type mentioned above.
The apparent sound reduction index may then be written
R
R
⎡
⎤
d
f
−
−
∑
R
′ =− ⋅
10 lg 10
10
+
10
10
.
(9.23)
⎢
⎥
⎢
⎥
⎣
⎦
