The application of the edge-constraint effect to nearly
Transcript of The application of the edge-constraint effect to nearly
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Purdue UniversityPurdue e-Pubs
Publications of the Ray W. Herrick Laboratories School of Mechanical Engineering
7-2002
The application of the edge-constraint effect tonearly-realistic noise control applicationsJ Stuart BoltonPurdue University, [email protected]
Bryan H. SongNASA-Kennedy Space Center
Follow this and additional works at: http://docs.lib.purdue.edu/herrick
This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] foradditional information.
Bolton, J Stuart and Song, Bryan H., "The application of the edge-constraint effect to nearly-realistic noise control applications"(2002). Publications of the Ray W. Herrick Laboratories. Paper 77.http://docs.lib.purdue.edu/herrick/77
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THE APPLICATION OF THE EDGE-CONSTRAINT EFFECT TO NEARLY-
REALISTIC NOISE CONTROL APPLICATIONS
Bryan H. Songy gNASA-Kennedy Space Center
J. Stuart Bolton Ray W. Herrick Laboratories
Purdue University
Purdue University Herrick Laboratories
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BackgroundBackground
• Investigation of edge constraint effect on samples placed in a modified standing wave tube (J. S. Bolton et al., SAE 1997; B H Song et al JASA 1999)1997; B. H. Song et al., JASA 1999).
• Internal constraints may be used to selectively enhance the transmission loss of lining materials at low frequencies (B. H S t l JASA 2001)H. Song et al., JASA 2001).
• Enhancement of the barrier performance of porous linings by using internal constraints (B. H. Song et al., submitted for NCEJ 2001).
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IntroductionIntroduction
• Comparison between measured and FE predicted random transmission losstransmission loss.
• Enhancement of transmission loss of barrier system by exploiting the edge-constraint effect at low frequency
• Design of low frequency noise control barriers following from constraint of porous lining materials around their edges.g
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Glass Fiber Material inside of Sample Holder
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Four Microphone Measurement
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Anechoic Transmission Loss (3” Sample A in a Small Tube)
40
(3 Sample A in a Small Tube)
30
35
Experiment Prediction using FEM (Edge constrained)Prediction using FEM (Unconstrained)
25
30
B)Increase in TL
Shearing mode
15
20
TL (d
Increase in TLdue to edge constraint
5
10
7 dB
102 103 1040
Frequency (Hz)
7 dB
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Surface Normal Impedance (3” Sample A in a Small Tube)
8
10Experiment
(3 Sample A in a Small Tube)
4
6
8R
e(zn
)Prediction using FEM (Edge constrained)Prediction using FEM (Unconstrained)
102 103 1040
2
5
n)
0
Im(z
n
102 103 104-5
Frequency (Hz)
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Poroelastic Material Properties used in Calculationsused in Calculations
Material Bulk density(Kg/m3)
Porosity Tortuosity Flow resistivity(MKS Rayls/m)
Shear modulus
(Pa)
Loss factor
(Pa)
Sample A 6.73 0.99 1.1 21000 1200 0.35
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Random Incidence Transmission Loss(27 cm X 27 cm)(27 cm X 27 cm)
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Schematic of Experimental Setup for the Random Transmission LossRandom Transmission Loss
R everb era tio nR (210 3)
F o am B arrie rsR everb era tio nR (210 3)
F o am B arrie rs
S am p les
R o o m (210 m 3)
S am p les
R o o m (210 m 3)
L o u d sp eaker 1A L T E C A 7X
L o u d sp eaker 2A L T E C A 7X
L o u d sp eaker 1A L T E C A 7X
L o u d sp eaker 2A L T E C A 7X
T ech ro nA m p lifie r 7520
D u a l M ic ro p h o n eS u p p ly(B & K 5935 )T ech ro n
A m p lifie r 7520
D u a l M ic ro p h o n eS u p p ly(B & K 5935 )
W ave tek F ilte r
A m p lifie r 7520
852W avetek F ilte r
852B & KP u lse
C o m p u te r
W ave tek F ilte r
A m p lifie r 7520
852W avetek F ilte r
852B & KP u lse
C o m p u te rR an d o m N o iseG en era to r
G R 1390 A
R an d o m N o iseG en era to rB & K 2032
C o m p u te rH P (V ec tra )R an d o m N o ise
G en era to rG R 1390 A
R an d o m N o iseG en era to rB & K 2032
C o m p u te rH P (V ec tra )
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The Circular Aperture for Random Incidence Transmission Loss (30 cm Diameter)Transmission Loss (30 cm Diameter)
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Axisymmetric and 3-D FE Models(30 cm Diameter Circular Aperture)(30 cm Diameter Circular Aperture)
Axisymmetric Model
3-D Model
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Internally-Constrained, 30 cm Diameter SampleSample
Mid mid ConstrainedMid-mid-Constrained Case
EdgeEdge
Mid
Mid-mid
Mid
Mid-mid
Mid-mid-midMid-mid-mid
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TL for the Various Constraint Cases
40Edge constrained (FE prediction)
30
35Edge constrained (Measurement) Mid constrained (FE prediction) Mid constrained (Measurement) Mid-mid constrained (FE prediction) Mid-mid constrained (Measurement)
20
25
L [d
B]
Mid-mid-mid constrained (FE prediction)Mid-mid-mid constrained (Measurement)
10
15
TL
5
10
102 1030
Frequency [Hz]
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TL for the Unconstrained FE Predictions
40Edge constrained
30
35Mid constrained Mid-mid constrained Mid-mid-mid constrained
20
25
L (d
B)
10
15
TL
5
10
102 1030
Frequency (Hz)
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FE Prediction of Random Incidence Transmission Loss (3-D Model)Transmission Loss (3 D Model)
SPL (1000 Hz)
ADX SDX
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FE Prediction of Random Incidence Transmission Loss (Axisymmetric FE Model)Transmission Loss (Axisymmetric FE Model)
SPL (1000 Hz)
ADX SDX
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The Square Aperture for Random Incidence Transmission Loss (27 cm by 27 cm)Transmission Loss (27 cm by 27 cm)
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Internally-Constrained, 27 cm by 27 cm SampleSample
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3-D FE Model (27 cm by 27 cm Square Aperture)(27 cm by 27 cm, Square Aperture)
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Internally-Constrained Green Sample(Frame Constraint)(Frame Constraint)
Glass fiber (3”)
B&K Two Microphone Probe
7.5 cm
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TL Increase for the Internally-Constrained Sample A (Frame Constraint)Sample A (Frame Constraint)
40
30
35
40
(a)
Measurement (Edge constraint) Measurement (Frame constraint) FE prediction (Edge constraint) FE prediction (Frame constraint)
20
25
30
(dB
)
10
15
20
TL
2 30
5
102 103
Frquency [Hz]
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TL for the Single Panel System Lined with Glass Fiber MaterialGlass Fiber Material
Limp Panel (0.078”)+Air (1”)+Glass fiber (3”)
B&K Two Microphone Probe
7.5 cm
2.5 cm
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TL Increase for the Internally-Constrained Sample A (Frame Constraint)Sample A (Frame Constraint)
40
30
35 (b)
20
25
L (d
B)
10
15
TL
102 1030
5
10 10Frquency [Hz]
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C l i
Good agreement between measured and FE predicted random
Conclusions
g ptransmission losses.
Random transmission losses through segmented lining materials were enhanced at low frequencies by the edge q y gconstraint effect.
Light and stiff fibrous materials combined with edge and internal constraint mechanisms can be used to design, light, g ghigh performance low frequency noise control barriers.