Building Acoustics

Sound transmission in buildings. Flanking transmission. 357

based on the power radiated from the various surfaces in the receiving room. The brick
walls here seems to be the weakest part, accounting for approximately 80% of the power
transmitted to the receiving room. To improve on the situation, measures have to be
applied on these walls.
As an example, we have added simple linings to these walls; 13 mm plasterboard
layers with a cavity depth of 50 mm, the cavity being filled with mineral wool. Linings
are added in both rooms and the results are shown in Figure 9.25. The weighted apparent
reduction index R ́w has now increased to 50.3 dB, and the power transmitted through the
partition and via the flanking elements is approximately equal.

63 125 250 500 1000 2000 4000

Frequency (Hz)

0

10

20

30

40

50

60

70

80

Sound

reduction index

R

' (dB)

Total

Lightweight wall

Concrete floors

Brick wall w/lining

Figure 9.25 Apparent sound reduction index of a lightweight double leaf wall with flanking brick walls with
linings. 180 mm concrete floors. Other curves indicate reduction index based on radiated power from the
pertinent elements in the receiving room. Predictions after Bastian®.

9.4 References

EN 12354–1: 2000, Building acoustics – Estimation of acoustic performance of buildings
from the performance of elements. Part 1: Airborne sound insulation between
rooms. [Parts 1–3 of this standard are adopted by ISO with number 15712 (from
2003).]