Etat de l’art des applicatifs en Vibro- Acoustique et ... · Etat de l’art des applicatifs en...

Etat de l’art des applicatifs en Vibro-Acoustique et des outils de recalage par la mesure

Arnaud Duval, Faurecia Acoustic Team

Journées Vibro-Acoustiques Numérique • Toulouse, 25 & 26 Novembre 2010

Journées Vibro-Acoustiques Numérique 2010 2Propertyof Faurecia-Duplication prohibited

Trim Broadband SimulationTowards the broadband vibro-acoustic model

20 250 1000 10000

Low Frequency

Global Modes Local Modes

Middle Frequency High Frequency

BEM-FEM Virtual SEA SEA / VASM

AST Core Numerical Expertise: Integrating porous trim materials in large vibro-acoustic models

Ray-Tracing methods


Trim Broadband SimulationIntroduction

� The introduction of curved trims in SEA or Virtual SEA models requires the obtention of two main parameters: � Damping Loss Factors (DLFs), which represent the damping induced

by the trims to the structure (or the absorption in a cavity).� Coupling Loss Factors (CLFs), which represent the modified radiation

efficiency of the structure induced by the trims (Insertion Loss) coupled to a cavity or a semi-infinite fluid (besides the potentially modified trimmed “structureborne” CLFs of the structure)..

� In order to take into account the curvature effects of 3D shaped trims, the novel technique consists in using poroelastic finite elements for getting the:� Curved Insertion Loss of the trims following the automatic sub-

structuring obtained with Virtual SEA.� Damping Loss Factors and Coupling Loss Factors of the trimmed

structure by carrying out an inverse SEA on the structureborne Frequency Response Functions simulated by a trimmed poroelastic FEM model in the middle frequency range.


Trim FEM Transmission Loss SimulationDash insulator cut out module: TL

Low and middle frequency dash trim FEM TransmissionLoss model: airborne noise

FEM

BEM emission

Air gap mesh between trim and

baffle

Structure steel (only coupling nodes are represented)

Felt / heavy layer trim

BEM reception

Diffuse field excitation

Air gap between structure and felt

FeltHeavy layer Air gap between

trim and baffle

Trim FEM

(Felt / Heavy layer with air gap)



Low and middle frequency dash trim FEM Transmission Loss model: airborne noise� Correlation Measurement / Simulation: Transmission Loss (dB)

125 250 500 1000 200020

25

30

35

40

45

50

55

60

65

70

Frequency [Hz]

Tra

nsm

issi

on L

oss

[dB

]

Measurement: Bare dash

Simulation VTM-TL: Bare dash

Measurement: Felt SC1200 HL3.9kg/m²

Simulation VTM-TL: Felt SC1200 HL3.9kg/m²

5 dB


Trim FEM Transmission Loss SimulationDash insulator cut out module: IL

Low and middle frequency dash trim FEM Transmission Loss model: airborne noise� Correlation Measurement / Simulation: Insertion Loss (dB)

125 250 500 1000 2000-5

0

5

10

15

20

25

30

35

40

Frequency [Hz]

Inse

rtion

Los

s [d

B]

Measurement: Felt SC1200 HL3.9kg/m²Simulation VTM-TL: Felt SC1200 HL3.9kg/m²

5 dB



Low and middle frequency dash trim FEM Transmission Loss model: airborne noise� Correlation Measurement / Simulation: Insertion Loss (dB)

Simulation with FTMM (FiniteTransfert Matrix Method),

according to the thickness 3D map of the dash insulator

(based on CAD)

125 250 500 1000 2000-10

-5

0

5

10

15

20

25

30

35

40

Frequency [Hz]

Inse

rtion

Los

s [d

B]



Simulation MAINE3A: Felt SC1200 HL3.9kg/m²

5 dB

==∑ τττ 1

log10TLSSi

ii



Low and middle frequency dash trim FEM Transmission Loss model: airborne noise� Correlation Measurement / Simulation: Transmission Loss (dB)

Simulation with FTMM (FiniteTransfert Matrix Method),

according to the thickness 3D map of the dash insulator

(based on CAD)

Simulation with IL from FTMM according to the thickness 3D

map + TL bare dash fromBEM/FEM computation

125 250 500 1000 200010

20

30

40

50

60

70

Frequency [Hz]

Tran

smis

sion

Los

s [d

B]


Simulation VTM-TL: Felt SC1200 HL3.9kg/m²Simulation MAINE3A: Felt SC1200 HL3.9kg/m²

Simulation FEM-MAINE3A: Felt SC1200 HL3.9kg/m²

10 dB



Low and middle frequency trim FEM Transmission Losscomputation with a simplified « fake » mesh of the structure

Mesh of the trim

Simplified « fake » meshof the dash structure

(clamped BC)

Meshing of the lower surface of the dash trimcoupled with structure

Actual mesh of the dash cutout module (clamped BC)

Only CAD of trim is required



Low and middle frequency trim FEM Transmission Lossmodel with simplified « fake » structure:� Simulation (real structure) / Simulation (simplified structure): TL (dB)

125 250 500 1000 20005

10

15

20

25

30

35

40

45

50

55

60

Frequency [Hz]

Tra

nsm

issi

on

Loss

[dB

]

Simulation VTM-TL: Bare dashSimulation VTM-TL (fake structure): Bare dash


Simulation VTM-TL (fake structure): Felt SC1200 HL3.9kg/m²

5 dB



Low and middle frequency trim FEM Transmission Loss model with simplified « fake » structure:� Correlation Measurement / Simulation : IL (dB)

125 250 500 1000 2000 4000-5

0

5

10

15

20

25

30

35

40

Frequency [Hz]

Inse

rtio

n Lo

ss [

dB]

Measurement: Felt SC1200 HL3.9kg/m²Simulation VTM-TL: Felt SC1200 HL3.9kg/m²Simulation VTM-TL (fake structure): Felt SC1200 HL3.9kg/m²

5 dB


Virtual SEA SimulationDash insulator cut out module

FEMModel geometry &

Modes computation

Virtual SEAMODAL SYNTHESIS: FRF and Input mobility computation

AUTO-SUBSTRUCTURING: Subsystems generationINVERSE SEA: Creation of reduced SEA model and processing

Experimental SEAINVERSE SEA: CLF, DLF, modal densities, equivalent masses,

power flow

SEA+DIRECT VSEA: runs Virtual SEA models with

analytical SEA coupling and frequency extension DIRECT SEA: pure analytical SEA models

Trim FEM

Inse

rtion

Los

s

FR

F &

mob

ility

Sub

-str

uctu

ring m

id-frequencyV

irtual SE

Am

odel

Geometry, Eigenmodes& Average damping

DLF

Measurements Trim FEM/BEM- TL

FRF

& m

obili

ty

FEMModel geometry &

Modes computation

FEMModel geometry &

Modes computation






power flow


power flow

SEA+DIRECT VSEA: runs Virtual SEA models with

analytical SEA coupling and frequency extension DIRECT SEA: pure analytical SEA models

Trim FEMTrim FEM

Inse

rtion

Los

s

FR

F &

mob

ility

Sub

-str

uctu

ring m

id-frequencyV

irtual SE

Am

odel

Geometry, Eigenmodes& Average damping

DLF

Measurements Trim FEM/BEM- TLTrim FEM/BEM- TL

FRF

& m

obili

ty


Virtual SEA SimulationDash insulator cut out module

Dash trim Virtual SEA / SEA+ Transmission Loss model: airborne path� Dash Virtual SEA „airborne“ substructuring valid between 500 Hz

and 2000 Hz (2228 modes)

6 subsystems: 477 reference nodes


Virtual SEA SimulationDash insulator cut out module: TL

Dash trim Virtual SEA / SEA+ Transmission Loss model: airborne path� Coupling with analytical SEA cavities and extension with analytical

SEA subsystems above 2000 Hz



Dash trim Virtual SEA / SEA+ Transmission Loss model: airborne path� Correlation Measurement / Simulation : Bare TL (dB)

125 250 500 1000 2000 400010

20

30

40

50

60

70

Frequency [Hz]

Tra

nsm

issi

on L

oss

[dB

]

Measurement: Bare dash

Simulation VTM-TL: Bare dashSimulation SEA+: Bare dash Virtual SEA

Simulation SEA+: Bare dash analytical

10 dB



Dash trim Virtual SEA / SEA+ Transmission Loss model: airborne path� Correlation Measurement / Simulation : Trimmed TL (dB)

125 250 500 1000 2000 400010

20

30

40

50

60

70

Frequency [Hz]

Tra

nsm

issi

on L

oss

[dB

]


Simulation VTM-TL: Felt SC1200 HL3.9kg/m²Simulation SEA+/VTM: Felt SC1200 HL3.9kg/m² dash Virtual SEA

Simulation SEA+/VTM: Felt SC1200 HL3.9kg/m² dash analytical

10 dB

Introduction of the trims as user defined Insertion Losses computed by simplified trim FEM IL simulation


125 250 500 1000 2000 400010

20

30

40

50

60

70

80

Frequency [Hz]

Tra

nsm

issi

on L

oss

[dB

]


Simulation VTM-TL: Felt SC1200 HL3.9kg/m²Simulation SEA+/VTM extrapo.: Felt SC1200 HL3.9kg/m² dash analy.

Simulation SEA+/MAINE3A: Felt SC1200 HL3.9kg/m² dash analytical

10 dB


Dash trim Virtual SEA / SEA+ Transmission Loss model: airborne path� Correlation Measurement / Simulation : Trimmed TL (dB)

Introduction of the trims as user defined Insertion Losses computed by simplified trim FEM IL simulation and extrapolated up to 4 kHz



Dash trim Virtual SEA / SEA+ Transmission Loss model: airborne path� Powerflow visualization at 630 Hz:


Virtual SEA SimulationDash insulator cut out module: structureborne

Dash trim Virtual SEA model: structureborne path� Dash Virtual SEA „structureborne“ substructuring valid between

500 Hz and 1000 Hz (831 modes)

4 subsystems: 596 reference nodes



Dash trim Experimental SEA model: structureborne path� Trimmed dash ESEA synthesized velocity correlation on SS3

(dash area)

50 observation nodes, 20 excitation nodeswith the reciprocal protocol



Dash trim FEM model: structureborne path� Correlation Measurement / Simulation : Fine Band at 1 node

Bare dash Trimmed dash

200 400 600 800 1000 1200-45

-40

-35

-30

-25

-20

-15

-10

-5

0

Frequency [Hz]

FRF

VTM Node: 386 (abs)

Measure Node: 386 (abs)5 dB

200 400 600 800 1000 1200-40

-35

-30

-25

-20

-15

-10

-5

0

5

Frequency [Hz]

frf

VTM Node: 386 (abs)

Measure Node: 386 (abs)

FRF

5 dB



Dash trim Virtual SEA / SEA+ model: structureborne path� Correlation Measurement / Simulation : Bare dash

500 1000-65

-60

-55

-50

-45

-40

-35

-30

-25

Frequency [Hz]

FR

F

Simulation SEA+: Bare dash SS1

Measurement SEA-Test: Bare dash SS15 dB

Different statistical content: 596 nodes vs. 70 nodes



Dash trim Virtual SEA / SEA+ model: structureborne path� Correlation Measurement / Simulation : Bare dash

500 1000-65

-60

-55

-50

-45

-40

-35

-30

-25

Frequency [Hz]

FR

F

Simulation SEA+: Bare dash SS2

Measurement SEA-Test: Bare dash SS25 dB

Different statistical content: 596 nodes vs. 70 nodes



Dash trim Virtual SEA / trim FEM model: structureborne� Correlation Measurement / Simulation : Trimmed dash

500 1000-20

-15

-10

-5

0

5

10

15

20

Frequency [Hz]

FR

F

Simulation VTM: trimmed dash SS2

Measurement shaker: trimmed dash SS25 dB

Same statistical content: 70 nodes vs. 70 nodes



Dash trim Virtual SEA / trim FEM model: structureborne� Correlation Measurement / Simulation : Trimmed dash

500 1000-20

-15

-10

-5

0

5

10

15

20

Frequency [Hz]

FR

F

Simulation VTM: trimmed dash SS3

Measurement shaker: trimmed dash SS35 dB

Same statistical content: 70 nodes vs. 70 nodes



Dash trim Virtual SEA / SEA+ model: structureborne path� Powerflow visualization at 630 Hz:

Ref: A. DUVAL and al., “Novel technique for the introduction of curved trims in SEA/Virtual SEA models using poroelastic finite elements in the middle (and high) frequency range.”, In Congrès SIA Confort automobile et ferroviaire, Le Mans (France), 2010.


Ray-Tracing SimulationVehicle Acoustic Synthesis Method

VASM methodology step by step description:

� Point 1 : Acoustic power measurement of each panel

- 1st Generation - 2nd Generation

Power measurements :Scanning intensity

)j(C).j(Q.c4

W 2

eq

2

)j( πρω= )j(C).j(Q.

c4W 2

eq

2

)j( πρω=

Qeq(J) determinationC(j): weighting• C(j)=2 for an hard reflecting wall• C(j)≈2-α for an absorbing surface

S(j)

Power measurements :Microflown®P-U probes


Ray-Tracing SimulationSource localization analysis

The main critical areas identified with the 3D intensity maps are:

� Instrument Panel Undercover

� Instrument Panel / Windscreen sealing

� Rear heel pad

� Carpet tunnel and sides

� Door sealings

� C-Pillar

� Air extraction

� Headliner sides

3D View



VASM Methodology step by step description:

� Point 2 : Transfer function

� Reciprocity Relation :

′′

=

2

r

2

i

2

i

2

r

Q

p

Q

p

FRF acquisition :Microflown/Classical pressure probes

Ray tracing methods calculations

Constant Volume Velocity Source: Q

Microphones

RECIPROCITY PRINCIPLE

H

Constant Volume Velocity Source: Q

Microphones

RECIPROCITY PRINCIPLE

H

W

DK

HdHk

S(j)



VASM Methodology step by step description:

� Point 3: SPL calculation at ear receiver point

� Uncorrelated monopoles. Validity : MF/HF

� SPL at the receiver point :)j(Q.Hp

n

1j

2

eq

2

r,j

2

r ∑=

=

1

SPLat the

receiver pointpr

2

Acoustic power Sm W(m)

Acoustic power S2 W(2)

Acoustic power S1 W(1) Q2eq(1)

Q2eq(2)

Q2eq(m)

H21,r

H2m,r

H22,r

X

X

X

+

1

SPLat the

receiver pointpr

2

Acoustic power Sm W(m)Acoustic power Sm W(m)

Acoustic power S2 W(2)Acoustic power S2 W(2)

Acoustic power S1 W(1)Acoustic power S1 W(1) Q2eq(1)

Q2eq(2)

Q2eq(m)

H21,r

H2m,r

H22,r

X

X

X

+

� The microflown technology allows to recompose run-ups


Ray-Tracing SimulationSerial measurement recomposition 4th Gear ICARE

FVASM (measured FRF) vs. Reference : ∆SPL (500-6300Hz) = 0.2 dB

FVASM (simulated FRF) vs. Reference : ∆SPL (500-6300Hz) = 0.1 dB

Front: Driver‘s position

Frequency [Hz]

5 dB(A)

250 500 1000 2000 4000

SP

L 4

thG

ear,

Fro

nt [d

B(A

)]

FVASM-FRF measuredReferenceFVASM-FRF ICARE

With Mock-ups


Ray-Tracing SimulationAcoustic package optimization loops

SPL(recomposition)

FRF(ICARE/Meas.)

Lw(Meas.)

Maine3A and/or SEA

MODELS

Thickness Distribution

∆TL/∆α

MODULE Optimization(ex : cockpit )

Meas. in Coupled Reverberating Rooms

Acoustic & Soft Trim

Materials Solutions


Optimized acoustic package :Measurement / Simulation Correlation

Driver's position

100 km/h, 4th gearMEASUREMENTS SIMULATIONS

SP

L [d

B(A

)]5

dB(A

)10

012

516

020

025

0

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

1000

0

Frequency [Hz]

dB(A) 500 Hz - 6.3 kHz :∆∆∆∆SPL= -4 dB(A)

AI :∆∆∆∆ = +14.4 %

SP

L [d

B(A

)]5

dB(A

)

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

1000

0

Frequency [Hz]

dB(A) 500 Hz - 6.3 kHz :∆∆∆∆SPL= -3.7 dB(A)

AI :∆∆∆∆ = +13.6 %


Ray-Tracing SimulationComparizon 4th Gear Lp Global 500-6300Hz [dB(A)]

Serial Optimized

Front Rear

Serial Optimized3D View3D View3D View3D View


Final measurements; WOT 2nd gearRun-ups recomposition results


Final measurements; WOT 2nd gearRun-ups recomposition results

5 dB(A)

1000 1500 2000 2500 3000 3500 4000 4500

rpm

SP

L (5

00

Hz

-6

.3 k

Hz)

[dB

(A)]

Microphone front left serial

Microphone front left optimized

Microphone front left serial (recomposition)

Microphone front left optimized (recomposition)

Filtered 500 Hz - 6.3 kHzdB(A): 3000 rpm - 3600 rpm

av eragemeasured / recomposed

Delta: -3.2 dB(A) / -3.1 dB(A)

10 %

1000 1500 2000 2500 3000 3500 4000 4500

rpm

Ext

end

ed

AI

[%]

Microphone front left serial

Microphone front left optimized

Microphone front left serial (recomposition)

Microphone front left optimized (recomposition)

Extended AI average3000 - 3600 rpm:

measured / recomposedDelta: +16.4 % / 11.5%

10 %

1000 1500 2000 2500 3000 3500 4000 4500

rpm

Ext

end

ed

AI

[%]

Microphone rear right serial

Microphone rear right optimized

Microphone rear right serial (recomposition)

Microphone rear right optimized (recomposition)

Extended AI average3000 - 3600 rpm:

measured / recomposed

Delta: +14.4 % / 14.0%

45

50

55

60

65

70

75

1000 1500 2000 2500 3000 3500 4000 4500

rpm

SP

L (5

00 H

z -

6.3

kHz)

[dB

(A)]

Microphone rear r ight serial

Microphone rear r ight optimized

Microphone rear r ight serial (recomposition)

Microphone rear r ight optimized (recomposition)

Filtered 500 Hz - 6.3 kHzdB(A): 3000 rpm - 3600 rpm

averagemeasured / recomposed

Serial : 62.9 dB(A) / 62.7 dB(A)Optim : 58.9 dB(A) / 59.0 dB(A)Delta: -4.0 dB(A) / -3.7 dB(A)

5 dB(A)


Trim Broadband SimulationConclusion

Towards the broadband vibro-acoustic model with trims:� This vibro-acoustic simulation study illustrates once again the

efficiency of combining FEM with inverse SEA approaches in the

middle frequency range, which is already known as Virtual SEA,

but also the pertinence of using trim FEM simulation, namely

poroelastic finite elements, within this modeling framework for an

accurate introduction of curved or 3D shaped trims under both

structureborne and airborne excitations.

� The results of the airborne Transmission Loss simulations

combining trim FEM with Virtual SEA simulations in the middle

frequency range up to 1250 Hz and SEA in the high frequency

range up to 4000 Hz here, by extrapolating the Insertion Loss

slopes, are very good and extremely promising.



Towards the broadband vibro-acoustic model with trims:� Indeed, considering the high curvature of this dash cut out module

compared to previous Transmission Loss investigations on floor

modules, this work seems to solve definitely the curvature issue of

trims with poroelastic finite element simulation.

� The structureborne vibro-acoustic responses computed with this

combined technique in the middle frequency range are giving good

results also and are therefore promising as well, even if some

further work is still to be done: trim FEM simulation will have to be

more integrated in the Virtual SEA process in the future…



Towards the broadband vibro-acoustic model with trims:� The Vehicle Acoustic Synthesis Method shows the pertinence of

combining SEA (computed Radiated Powers in a cavity) with Ray-

Tracing simulations (computed Frequency Response Functions) in

order to improve the spatial information content of SEA in the

middle and high frequency.

� The combination of BEM-FEM, Virtual SEA / SEA and Ray-Tracing

simulation methods brings the hope to access in the near future to

a fully numerical broadband vibro-acoustic model…


Thank you for your attention…

Etat de l’art des applicatifs en Vibro- Acoustique et ... · Etat de l’art des applicatifs en...

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Transcript of Etat de l’art des applicatifs en Vibro- Acoustique et ... · Etat de l’art des applicatifs en...