2b PRESENTATION
27
Sound Insulation of Timber Framed Structures THE EIGHTH WESTERN PACIFIC ACOUSTICS CONFERENCE Keith Ballagh
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Training
Transcript of 2b PRESENTATION
Sound Insulation of Timber Framed
Structures
THE EIGHTH WESTERN PACIFIC ACOUSTICS
CONFERENCE
Keith Ballagh
Timber Framed Buildings• Advantages
– Economical– Earthquake resistant– Quick construction time– Light weight– Easily modified
• Disadvantages– Less durable– Limited height– Acoustic performance
can be poor.
Historical Trends in Sound InsulationRw (dB)
Scrim and sarking 15-20 (est)Lath and plaster 30Split stud 43Staggered stud 45Resilient rail 48Isolated Stud/Resilient clip 50
Factors affecting sound insulation• Mass Law• Cavity Walls• Effect of absorptive infill• Connections between linings• Methods of isolating linings• Leakage• Flanking
The Mass Law
The Mass Law
f < fc 48)(20 −= mfLogR
48)/2(10)(20 −−= cLogmfLogR πωηωf > fc
Cavity Wall Performance
48))((20 21 −+= mmfLogR
29)(2021 −++= fdLogRRR
621 ++= RRR
Ideal Double Wall Behaviour
Effect of Cavity Absorption
STC 65
STC 55
Effect of Connections to Frame
0
10
20
30
40
50
60
70
80
90
100
50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000
One third octave band centre frequency (Hz)
Tran
smis
sion
Los
s (d
B)
18 dB/octave(region 2)
12 dB/octave (region 3)
6 dB/octave(region 3)
fo f l
∆TL
No connections between panelseg double stud
Bridging between panelseg single stud wallmass law
(region 1)
18)]/([20).(10
211
21
−+++= +
mmmLogfbLogRR c
Effect of Connections to Frame
Behaviour of panel fixings
Methods of isolating wall linings
Methods of isolating wall linings
Quietzone Acoustic FramingResilient Sound Isolation Clip
Resilient fastenings of Linings
Substitution of Generic Components
STC 52
STC 45
Effect of Leakage
Effect of Leakage
Prediction of Flanking Transmission
A simple expression for flanking transmission Rf
⎟⎟⎠
⎞⎜⎜⎝
⎛++−=
fif A
ALoglossJointRR 10log10 σ
WhereRf is the flanking transmissionRi is the transmission of the flanking elementA is the area of the main partitionAf is the area of the flanking element which radiates into the receive room
Measured Radiation Efficiency
Radiation of plasterboard wall
-25.0
-20.0
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
63 125 250 500 1000 2000 4000 8000
frequency (Hz)
Rad
iatio
n Ef
ficie
ncy
(dB
)
average measured theory (stud width) theory (whole area)
Measured Radiation EfficiencyRadiation of plasterboard wall
-25.0
-20.0
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
63 125 250 500 1000 2000 4000 8000
f req uency ( Hz)
average measured theory (stud width) theory (whole area)
Attenuation of structure-borne soundAttenuation at right angles to the studs
0
5
10
15
20
25
0 0.6 1.2 1.8 2.4 3 3.6 4.2distance from excitation point (metres)
atte
nuat
ion
(dB)
50-10kHz
50-125Hz
200-2kHz
Attenuation of structure-borne soundAttenuation in the direction of the studs
-5
0
5
10
15
20
25
0 0.3 0.6 0.9 1.2distance from excitation point (metres)
atte
nuat
ion
(dB)
50-10kHz
50-125Hz
200-2kHz
Flanking Transmission
High performance walls
Thickness (mm)
Mass (kg)
2x16mm plasterboard on 2x100x50 studs
290 68 kg/m2
400mm Solid concrete blocks
400 900kg/m2
Conclusions• Timber framed construction has significant
practical advantages• Sound Insulation has traditionally been
perceived as a disadvantage• Techniques are available to achieve high sound
insulation• High performance designs are vulnerable to
poor construction
