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