Building Acoustics

352 Building acoustics

(9.43)

2

12

2

13

8.7 5.7 (dB),

8.7 17.1 5.7 ( dB),

KM

KMM

=+⋅

=+ ⋅+⋅

where M is the logarithmic ratio

mass/area of element ( )

lg.

mass/area of element

ji

M

i

⎡⎤⊥

= ⎢

⎣⎦

⎥ (9.44)

It should be noted that these expressions are assumed to be frequency independent.

9.3.2.3 Some examples of Dv,ij and Kij

Expressions given in the standard EN 12354 are based on a number of measurement
results, both from laboratory experiments and from in situ observations. As expected,
data for massive, heavy constructions are more commonly available than for lightweight,
multilayered type of constructions. Estimating transmission along lightweight façades
may be a real challenge. One should expect that the amount of data will increase with a
prolonged use of prediction models such as given in EN 12354.

150 mm

125 mm

120 mm

7 mm

rubber

63 125 250 500 1000 2000 4000

Frequency (Hz)

0

10

20

30

40

50

60

70

80

Vib

ration velocity level diffe

rence

D

(dB)ij

No layer

On upper side

On lower side

On both sides

Figure 9.21 Measured vibration level differences in a test building of aerated aggregate concrete. Elastic layers
(foam rubber) between wall and floor slabs. After Huse (1972).