Laboratory of Acoustics and Laboratory of Building PhysicsKatholieke Universiteit Leuven
Celestijnenlaan 200DB-3001 Leuven, BELGIUMhttp://fys.kuleuven.be/atf
A comparison between the structure-borne sound generated by a low-frequency
vibrating plate mounted on a light-weight structure and on a heavy-weight structure
Pieter Schevenels, Lieven De Geetere, Nathalie Geebelen, Gerrit Vermeir, Bart Ingelaere
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
2/13
Outline
1. Introduction2. Experimental setup3. Mobilities4. Predicted and measured sound pressure
levels5. Conclusions
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
3/13
1. Introduction ...
• Background- Flow of power
• Injection from source into structure• Distribution over structure• Radiation from structure into room
- EN 12354-5 •
Installed power ...
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
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Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
4/13
... Introduction ...
• Background- Installed power (1D, single contact point)
•
– Measuring F ...– Only in situ ...
•
– Source and receiver ...– Measuring vsf ...
• Reception plate method
– (force source assumption)
–
*12
W F v Source or receiver
Equivalent velocity source
Equivalent force source
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Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
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Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
5/13
... Introduction
• Background- Installed power (1D, three contact points)
• Point mobilities Ykk and transfer mobilities Ykl
– Matrix formulation → lots of variables to measure
• Concept of effective mobilities– Incorporate all mobilities into one effective mobility YΣ
– Assumptions about forces in different contact points» Equal» Random phase
→
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
3
, ,1
1Re Re
3i k i kkk
Y Y
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
6/13
2. Experimental setup ...
• Vibrating plate- 24, 40 and 60 Hz- Amplitude: 3 mm
• Reception plate- 2.0 x 2.8 m²- Thickness: 10 cm- Resiliently mounted
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
7/13
... Experimental setup ...
• Floor plates (resiliently mounted)- Wooden floor (3.0 x 3.0 m²)
• Thickness: 25 cm– Fibreboard– 7 wooden joists with glass wool– 2 gypsum board plates
- Concrete floor (2.0 x 2.0 m²)• Thickness: 10 cm
- Floating floor (1.5 x 1.5 m²)• Thickness: 10 + 3 + 5 cm
– Mineral wool layer– Light-density concrete plate
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
8/13
... Experimental setup
• Necessary data to predict SPL in lower room- Source characteristics
• Airborne sound power level LWa
• Structure-borne sound power level LWsn into reception plate
- Plate characteristics• Mobility Y• Internal loss factor η• Airborne sound insulation R
- Room characteristics• Reverberation time T• Volume V
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
9/13
3. MobilitiesIntroduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
63 125 250 500 1000 200010
-7
10-6
10-5
10-4
10-3
Frequency [Hz]Ave
rage
rea
l par
t of
eff
ectiv
e re
ceiv
er m
obili
ty [
m/N
s]
Wooden floorConcrete floorFloating floorReception plate
3
, ,1
1Re Re
3i k i kkk
Y Y
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
10/13
63 125 250 500 1000 20000
20
40
60
80
100
Frequency [Hz]
Lp [
dB
(L)]
(re
2 1
0-5
Pa
)
Predicted SPLMeasured SPL
4. Predicted and measured SPLs ...
• Wooden floor
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
→ Force source assumption invalid at high mobility
Operating frequency: 40 Hz
,Re i kY
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
11/13
63 125 250 500 1000 20000
20
40
60
80
100
Frequency [Hz]
Lp [
dB
(L)]
(re
2 1
0-5
Pa
)
Predicted SPLMeasured SPL
... Predicted and measured SPLs ...
• Floating floor
→ Force source assumption valid at low mobility
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
Operating frequency: 40 Hz
,Re i kY
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
12/13
63 125 250 500 1000 20000
20
40
60
80
100
Frequency [Hz]
Lp [
dB
(L)]
(re
2 1
0-5
Pa
)
Predicted SPLMeasured SPL
63 125 250 500 1000 20000
20
40
60
80
100
Frequency [Hz]
Lp [
dB
(L)]
(re
2 1
0-5
Pa
)
Predicted SPLMeasured SPL
63 125 250 500 1000 20000
20
40
60
80
100
Frequency [Hz]
Lp [
dB
(L)]
(re
2 1
0-5
Pa
)
Predicted SPLMeasured SPL
Operating frequency: 60 HzOperating frequency: 40 Hz
... Predicted and measured SPLs
• Concrete floor
→ FSA must be valid for all frequencies→ FSA seems to be dependent on operation frequency
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions
Operating frequency: 24 Hz
,Re i kY
Inter-noise 2007, Istanbul29th of August 2007
A comparison between the structure-borne sound ...Pieter Schevenels et al.
13/13
5. Conclusions
• Reception plate method- Easy method- Fewer measurements- Relatively accurate predictions
• Force source assumption- Possibly still good predictions when Ys is low
- But bad predictions at all frequencies when operating frequency lies in a frequency band where Ys ≈ Yi
→ Black-box model of source invalid→ Reaction forces do influence source behaviour
Introduction – Experimental setup – Mobilities – Predicted and measured SPLs – Conclusions