Civil Engineering Reference
In-Depth Information
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Figure 4.3
Transfer function between sound pressure and monopole source volume acceleration in a room of
dimensions 6.2 x 4.1 x 2.5
metres and reverberation time 1.0 seconds. Source position (1.7, 1.0, 1.5), receiver
position (3.5, 2.5, 1.5). Thick solid curve - analysis in one-third-octave bands. Dashed line - diffuse-field
model. The points show calculated resonance frequencies.
Frequency (Hz)
The response is also shown resulting from an analysis in one-third-octave bands, a
normal procedure when performing measurements in buildings. It is then of interest to
calculate the result if one is using a simple diffuse field model for this case (see section
4.5.1
below). Assuming that the pressure at the receiver position is not affected by the
direct field from the source, we may use the simple relationship between the source
power
W
and the average sound pressure in the room stating that
2
2
p
p
55.3
⋅
V
W
=
⋅ =
A
⋅
,
(4.19)
4
ρ
c
4
ρ
c
c
T
00
00
0
where
A
is the total absorbing area in the room. A monopole source freely suspended in
the room will radiate a power
22
ρ
ck Q
00
W
=
.
(4.20)
monopole
4
π
Equating these powers, we obtain
p
Q
cT
0
=
ρ
.
(4.21)
0
ω
55.3
π
V
