Building Acoustics

354 Building acoustics

63 125 250 500 1000 2000 4000

Frequency (Hz)

0

10

20

30

40

50

60

70

80

D

and ij

K

(dB)ij

Dij

Kij

Wooden floor on joist

100 mm concrete

(lightweight)

4 x130 mm PUR

180 mm concrete

4x88 mm PUR

Figure 9.22 Vibration reduction index Kij and velocity level differences Dij with elastic layers on both sides of
joint. Measurement data from a dwelling by Brøsted Pedersen (1993).

Each of these flanking reduction indexes Rf may be expressed by Equation (9.33),
which combined with the appropriate vibration reduction index Kij using Equation (9.41)
gives

S

10 lg.

2

ij ij

ij ij

ij i j

RR Saa

RK

lSS

+ ⎡ ⎤

=++⋅⎢ ⎥

⎢⎣ ⎥⎦

(9.46)

This expression found in EN 12354–1 was derived in a similar way as outlined in section
9.3.1. As mentioned in section 9.3.2.2 a relationship between the vibration reduction
index Kij and the coupling loss factor ηij according to a SEA model may be established.
Indeed, using the framework of SEA, Nightingale and Bosmans (2003) arrive at an
identical expression for R ́, under the condition that the flanking reduction indexes apply
to resonant transmission only. The added advantage, by using SEA, is that this enables
them to formulate criteria to assess the suitability of the expressions in particular
situations.
Besides finding proper estimates for Kij relevant for the actual in situ situation,
there remains the problem of finding corresponding data for the structural damping given