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, bolton@purdue.edu

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 epubs@purdue.edu 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

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

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).

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

Glass Fiber Material inside of Sample Holder

Four Microphone Measurement

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

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)

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

Random Incidence Transmission Loss(27 cm X 27 cm)(27 cm X 27 cm)

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 )

The Circular Aperture for Random Incidence Transmission Loss (30 cm Diameter)Transmission Loss (30 cm Diameter)

Axisymmetric and 3-D FE Models(30 cm Diameter Circular Aperture)(30 cm Diameter Circular Aperture)

Axisymmetric Model

3-D Model

Internally-Constrained, 30 cm Diameter SampleSample

Mid mid ConstrainedMid-mid-Constrained Case

EdgeEdge

Mid

Mid-mid

Mid

Mid-mid

Mid-mid-midMid-mid-mid

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]

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)

FE Prediction of Random Incidence Transmission Loss (3-D Model)Transmission Loss (3 D Model)

SPL (1000 Hz)

ADX SDX

FE Prediction of Random Incidence Transmission Loss (Axisymmetric FE Model)Transmission Loss (Axisymmetric FE Model)

SPL (1000 Hz)

ADX SDX

The Square Aperture for Random Incidence Transmission Loss (27 cm by 27 cm)Transmission Loss (27 cm by 27 cm)

Internally-Constrained, 27 cm by 27 cm SampleSample

3-D FE Model (27 cm by 27 cm Square Aperture)(27 cm by 27 cm, Square Aperture)

Internally-Constrained Green Sample(Frame Constraint)(Frame Constraint)

Glass fiber (3”)

B&K Two Microphone Probe

7.5 cm

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]

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

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]

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.