Civil Engineering Reference
In-Depth Information
An estimate for the radiation factor σ could be 0.05-0.1 in the chosen frequency band as
the critical frequency is approximately equal to 2500 Hz. In effect, we may neglect this
term and transform Equation
(7.16)
into
22
2
u
ω
a
2
0
π
ρ
c
chc m
12
=
≈
,
(7.17)
2
2
2
p
p
00
L
where
a
denotes the acceleration. A sound pressure level of 100 dB corresponds to a
sound pressure of 2 Pa, which gives
2
⎛⎞
2
m
a
2
a
=
17.3
, or expressed as an acceleration level
L
=⋅
10 lg
≈
132 dB
.
⎜
⎜
⎝⎠
a
4
2
0
s
a
The reference value
a
0
is 10
-6
m/s
2
. Expressed as a RMS-value, the acceleration is
thereby 4.2 m/s
2
(or approximately half the acceleration of gravity).
It should, however, be no problem to increase the internal loss factor by a factor of
100 by applying a visco-elastic layer to the plate, resulting in a η
2
of 10
-2
. (What will be
the effect on the acceleration level?)
7.4
SEA APPLICATIONS IN BUILDING ACOUSTICS
Based on the early applications of SEA, in particular on calculating the response of panel
constructions in reverberant sound fields (see e.g. Maidanik (1962)), the method gained
acceptance for solving building acoustic problems such as transmission through single
and double wall constructions (Crocker and Price (1969); Price and Crocker (1970)).
Transmission through constructions containing several layers such as double walls will
be treated in the next chapter and we shall then include examples where SEA models are
used.
4
4
5
5
1
1
2
2
3
3
Figure 7.4
Sound transmission between two rooms by way of a separating wall and flanking walls.
It will be appropriate when presenting this short overview to use another building
acoustic problem as an example, namely the sound transmission between two rooms
including sound transmission by way of flanking walls. As we shall see later (see
Chapter 9), there will be classical models to estimate both the direct transmission and the
