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Presentation at 2013 SAE NVH Conference May 22, 2013 NVH Structure Borne NVH Workshop
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2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 1
SAE 2013 NVH ConferenceStructure Borne NVH Workshop
Alan DuncanAlan Duncan Altair Engineering @ HondaNVH Specialist
Greg Greg GoetchiusGoetchius Tesla MotorsNVH Specialist
JianminJianmin GuanGuan Altair Engineering NVH Manager
Contact Email: [email protected]
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 2
Structure Borne NVH WorkshopWorkshop Objectives -1. Review Basic Concepts of Automotive Structure Borne Noise.
2. Propose Generic Targets.
3. Present New Technology Example.
Intended Audience �• New NVH Engineers.
• �Acoustics� Engineers seeking new perspective.
• �Seasoned Veterans� seeking to brush up skills.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 3
Structure Borne NVH Workshop• Introduction• Low Frequency Basics• Mid Frequency Basics• Live Noise Attenuation Demo• New Technology
Uncertainty and NVH Scatter • Closing Remarks
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 4
Structure Borne NVH Workshop• Introduction• Low Frequency Basics• Mid Frequency Basics• Live Noise Attenuation Demo• New Technology
Uncertainty and NVH Scatter• Closing Remarks
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 5
Rideand
Handling
NVH Durability
ImpactCrashWorthiness
Competing Vehicle Design Disciplines
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 6
Automotive Engineering Objectives are Timeless
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 7
Structure Borne NVH Workshop• Introduction• Low Frequency Basics• Mid Frequency Basics• Live Noise Attenuation Demo• New Technology
Uncertainty and NVH Scatter• Closing Remarks
Alan Duncan
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 8
Structure Borne Noise and Vibration
VibratingSource
Frequency Range: up to 1000 HzSystem Characterization
• Source of Excitation• Transmission through Structural Paths • “Felt” as Vibration• “Heard” as Noise
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 9
Structure Borne NoiseAirborne Noise
Res
pons
e
Log Frequency
�Low�Global Stiffness
�Mid�
Local Stiffness+
Damping
�High�
Absorption+
Mass+
Sealing+
Damping
~ 150 Hz ~ 1000 Hz ~ 10,000 Hz
Automotive NVH Frequency Range
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 10
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 11
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 12
RECEIVER
PATH
SOURCE
Structure Borne NVH Basics
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 13
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 14
m
APPLIED FORCE
F = FO sin 2 π f t
k c FT
TR = FT / F
TransmittedForce
Single Degree of Freedom Vibration
= fraction of critical damping
fn = natural frequency
f = operating frequency
( )2n
22n
2
2n
ff2)ff(1)ff(21ζ
ζ+−
+=
ζmk
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 15
0 1 2 3 4 50
1
2
3
4Tr
ansm
issi
bilit
y R
atio
1.414Frequency Ratio (f / fn)
Vibration Isolation Principle
m
APPLIED FORCEF = FO sin 2 π f t
k c FT
TR = FT / F
TransmittedForce
Isolation RegionIsolation Region
1.00.5
0.375
0.25
0.15
0.1
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 16
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 17
Two Main Sources
NVH Source Considerations
Suspension Powertrain
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 18
Typical NVH Pathways to the Passenger
PATHS FOR
STRUCTURE BORNE
NVH
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 19
Structure Borne NVH Sources
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 20
Structure Borne NVH Sources
Primary Consideration:
Reduce the Source first as much as possible because whatever enters the structure is transmitted through multiple paths to the receiver.
Transmission through multiple paths is more subject to variability.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 21
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 22
Receiver ConsiderationsSubjective to Objective Conversions
Subjective NVH Ratings are typically based on a 10 Point Scale resulting from Ride Testing
A 2 ≈≈≈≈ 1/2 A 1Represents 1.0 Rating Change
TACTILE: 50% reduction in motion
SOUND : 6.dB reduction in sound pressure level ( long standing rule of thumb )
Receiver Sensitivity is a Key Consideration
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 23
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 24
Total 2178.2 Kg (4800LBS)Mass Sprung 1996.7 Kg
Unsprung 181.5 Kg (8.33% of Total)Powertrain 181.5 Kg
Tires 350.3 N/mmKF 43.8 N/mmKR 63.1 N /mmBeam mass lumped on grids like a beam M2,3,4 =2 * M1,5
Symbolic Model of Unibody Passenger Car8 Degrees of Freedom
From Reference 6
318
2
6
4
75
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 25
1 2 4 5
6 7
8
3
TiresWheels
SuspensionSprings
Engine Mass
EngineIsolator
Flexible Beam for Body
8 Degree of Freedom Vehicle NVH Model
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 26
8 Degree of Freedom Vehicle NVH ModelForce Applied to Powertrain Assembly
Forces at Powertrain could represent a First OrderRotating Imbalance
Feng
1 2 4 5
6 7
8
3
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 27
Engine Isolation Example
Response at Mid Car
0.0001
0.0010
0.0100
0.1000
1.0000
5.0 10.0 15.0 20.0Frequency Hz
Velo
city
(mm
/sec
)
Constant Force Load; F ~ A 15.9 Hz8.5 Hz7.0 Hz
700 Min. RPM First Order UnbalanceOperation Range of Interest
318
2
6
4
753311
8822
66
44
7755
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 28
Engine Isolation Example
Response at Mid Car
0.0001
0.0010
0.0100
0.1000
1.0000
5.0 10.0 15.0 20.0Frequency Hz
Velo
city
(mm
/sec
)
Constant Force Load; F ~ A
700 Min. RPM First Order UnbalanceOperation Range of Interest
318
2
6
4
753311
8822
66
44
7755
15.9 Hz
8.5 Hz
7.0 Hz
Engine Idle Speed Operating Shapes
at 700 RPM
Lowest Body Movement
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 29
Concepts for Increased Isolation�Double� isolation is the typical strategy for further improving isolation of a given vehicle design.
Subframe is Intermediate Structure
Suspension Bushing is first level
Second Level of Isolation is at Subframe
to Body Mount
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 30
8 Degree of Freedom Vehicle NVH ModelRemoved Double Isolation Effect
WheelMass
Removed
1 2 4 5
6 7
8
3
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 31
Double Isolation ExampleVertical Response at DOF3
0.0E+00
1.0E+00
2.0E+00
3.0E+00
4.0E+00
5.0E+00
6.0E+00
5.0 10.0 15.0 20.0Frequency Hz
Velo
city
(m
m/s
ec)
Base Model
Without Double_ISO
1.414*fn
318
2
6
4
753311
8822
66
44
7755
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 32
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 33
Mode Management Chart
0 5 10 15 20 25 30 35 40 45 50HzFirst Order Wheel/Tire Unbalance V8 Idle
Hot - Cold
EXCITATION SOURCESInherent Excitations (General Road Spectrum, Reciprocating Unbalance, Gas Torque, etc.)Process Variation Excitations (Engine, Driveline, Accessory, Wheel/Tire Unbalances)
Hz
Hz0 5 10 15 20 25 30 35 40 45 50
0 5 10 15 20 25 30 35 40 45 50
CHASSIS/POWERTRAIN MODES
Ride ModesPowertrain Modes
Suspension Hop and Tramp ModesSuspension Longitudinal Modes
Exhaust Modes
BODY/ACOUSTIC MODES
Body First Bending First Acoustic Mode
Steering Column First Vertical BendingBody First Torsion
(See Ref. 1)
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 34
8 Degree of Freedom Vehicle NVH ModelBending Mode Frequency Separation
Beam Stiffness was adjusted to align Bending
Frequency with Suspension Modes and then
progressively separated back to Baseline.
1 2 4 5
6 7
8
3
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 35
Response at Mid Car
0.10
1.00
10.00
100.00
5 10 15 20Frequency Hz
Velo
city
(mm
/sec
)
18.2 Hz Bending13.Hz Bending10.6 Bending
8 DOF Mode Separation Example
18.2 Hz13.0 Hz
10.6 Hz318
2
6
4
753311
8822
66
44
7755
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 36
Response at Mid Car
0.10
1.00
10.00
100.00
5 10 15 20Frequency Hz
Velo
city
(mm
/sec
)
18.2 Hz Bending13.Hz Bending10.6 Bending
8 DOF Mode Separation Example
All Operating Shapes at 10.6 Hz
318
2
6
4
753311
8822
66
44
7755 Highest Body Bending
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 37
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 38
Front input forces Rear input forces
First Bending: Nodal Point Mounting ExampleMount at Nodal Point
Locate wheel centers at node points of the first bending modeshapeto prevent excitation coming from suspension input motion.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 39
Passenger sits at node point for First Torsion.
Side View
First Torsion: Nodal Point Mounting ExamplesMount at Nodal Point
Transmission Mount of a3 Mount N-S P/T is nearthe Torsion Node.
Rear View
Engine
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 40
Powertrain Bending Mode Nodal Mounting
Mount system is placed to support Powertrain at the Nodal Locations of the First order Bending Mode. Best compromise with Plan View nodes should also be considered.
1 2 4 5
6 7
3
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 41
1 2 4 5
6 7
8
3
8 Degree of Freedom Vehicle NVH ModelBending Node Alignment with Wheel Centers
Redistribute Beam Masses to move Node Points to
Align with points 2 and 4
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 42
Response at Mid-Car
0.0E+00
1.0E+00
2.0E+00
3.0E+00
4.0E+00
5.0 10.0 15.0 20.0Frequency Hz
Velo
city
(m
m/s
ec)
Node ShiftedBase Model
First Bending Nodal Point Alignment
318
2
6
4
753311
8822
66
44
7755
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 43
Response at Mid-Car
0.0E+00
1.0E+00
2.0E+00
3.0E+00
4.0E+00
5.0 10.0 15.0 20.0Frequency Hz
Velo
city
(m
m/s
ec)
Node ShiftedBase Model
First Bending Nodal Point Alignment
318
2
6
4
753311
8822
66
44
7755
Operating Shapes at
18.2 Hz
Node Shifted Model
No Residual Body Bending
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 44
Diagnosis: Increase at 10.2 Hz
Body Bends up at Downward Position of Cycle
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 45
Diagnosis: Increase at 10.2 Hz
Motion Experienced when Bending is Present
Motion Experienced when Bending is Removed
Diagnosis: Increase at 10.2 Hz
Center - Undeformed Position
Up Position
Down Position
CONCLUSION:Response Increases when a Beneficial mode is Removed.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 46
Low Frequency Basics• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 47
YO
xSDOF
Dynamic Absorber Concept
MYO
x
Auxiliary Spring-Mass-Damperm = M / 10
2DOFM
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 48
Powertrain Example of Dynamic Absorber
Anti-Node Identifiedat end of Powerplant
k c
Absorber attached at anti-node acting in the Vertical and Lateral plane.
Tuning Frequency = √√√√ k/m
m
[Figure Courtesy of DaimlerChrysler Corporation]
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 49
Baseline Sound Level63 Hz Dynamic Absorber63 + 110 Hz Absorbers
Baseline Sound Level63 Hz Dynamic Absorber63 + 110 Hz Absorbers
[Figure Courtesy of DaimlerChrysler Corporation]
10 dB
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 50
Low Frequency Basics - Review• Source-Path-Receiver Concept• Single DOF System Vibration• NVH Source Considerations• Receiver Considerations• Vibration Attenuation Strategies
Provide Improved IsolationMode ManagementNodal Point MountingDynamic Absorbers
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 51
Structure Borne NVH Workshop• Introduction• Low Frequency Basics• Mid Frequency Basics• Live Noise Attenuation Demo• New Technology
Uncertainty and NVH Scatter• Closing Remarks
Jianmin Guan
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 52
Mid Frequency NVH Fundamentals
This looks familiar!Frequency Range of Interest has changed to
150 Hz to 1000 Hz
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 53
Typical NVH Pathways to the Passenger
PATHS FOR
STRUCTURE BORNE
NVHNoise Paths are the
same as LowFrequency Region
Noise Paths are thesame as Low
Frequency Region
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 54
Mid-Frequency Analysis CharacterStructure Borne Noise
Airborne Noise
Res
pons
e
Log Frequency�Low�
Global Stiffness�Mid�
Local Stiffness+
Damping
�High�
Absorption+
Mass+
Sealing
~ 150 Hz ~ 1000 Hz ~ 10,000 Hz
High modal densityand coupling in
source, path andreceiver
• Mode separation is less practical inmid-frequency
• New Strategy is Effective Isolation:Achieved by reducing energy transferlocally between source and receiver atkey paths.
•• Mode separation is less practical inMode separation is less practical inmidmid--frequencyfrequency
•• New Strategy is Effective Isolation:New Strategy is Effective Isolation:Achieved by reducing energy transferAchieved by reducing energy transferlocally between source and receiver atlocally between source and receiver atkey paths.key paths.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 55
Mid-Frequency Analysis Character
Control Measures for Mid Frequency Concerns
Effective Isolation
Attenuation along Key Noise Paths
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 56
Mid-Frequency Analysis Character
Control Measures for Mid Frequency Concerns
Effective Isolation
Attenuation along Key Noise Paths
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 57
Classical SDOF: Rigid Source and Receiver
Tra n
smis
sibi
l ity
Ra t
io
1.0 1.414 10.0
f / f n
�Real Structure�Flexible (Mobile)Source and Receiver
Isolation Effectiveness
Effectiveness deviates from the classical development as resonances occur in the receiver structure and in the foundation of the source.
Isolation RegionIsolation Region
1.0
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 58
Mobility• Mobility is the ratio of velocity response at the excitation point on structure
where point force is applied
Mobility =Velocity
Force
• Mobility, related to Admittance, characterizes Dynamic Stiffness of the structure at load application point
Mobility =Frequency * Displacement
Force
=Frequency
Dynamic Stiffness
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 59
• The isolation effectiveness can be quantified by a theoretical model based on analysis of mobilities of receiver, isolator and source
• Transmissibility ratio is used to objectively define measure of isolation
TR =Force from source without isolator
Force from source with isolator
Isolation
V r
V ir
V is
F r
F ir
Receiver
Source
F is
Fs V s
Isolator
VF s=
Y i + Y r + Y s
V r
F r
Receiver
Source
F s V s
VF s=
Y r + Y s
VV
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 60
TR = ( Y r + Y s ) //// ( Y i + Y r + Y s )
• For Effective Isolation (Low TR) the Isolator Mobility must exceed the sum of the Source and Receiver Mobilities.
Y r : Receiver mobility
Y s : Source mobility
Y i : Isolator mobility
V m
V im
V if
F m
F im
Receiver
Source
F if
F f V f
Isolator
TR = Force from source without an isolator Force from source with an isolator
Isolation
Recall that K 1Y ∝
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 61
TR = ( ) //// ( ) K body
1K source
1+ K body
1 + K iso
1K source
1+
K iso
K sourceK body
K iso1.0 5.0 20.0
1.0
5.0
20.0
0.67 0.55 0.51
0.55 0.29 0.20
0.51 0.20 0.09
Generic targets:body to bushing stiffness ratio of at least 5.0source to bushing stiffness ratio of at least 20.0
Designing Noise Paths
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 62
Body-to-Bushing Stiffness RatioRelationship to Transmissibility
Stiffness Ratio; K body / K iso
Tran
smis
sibi
lity
Rat
io T
R
0
0.1
0.2
0.3
0.4
0.5
0.6
1 2 3 4 5 6 7 8 9 10
Target Min. = 5 gives TR = .20
For a source ratio of 20
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 63
Mid-Frequency Analysis Character
Control Measures for Mid Frequency Concerns
Effective Isolation
Attenuation along Key Noise Paths
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 64
Identifying Key NVH PathsKey NVH paths are identified by Transfer Path Analysis (TPA)
Fi
TactileTransferTactile
TransferAcousticTransfer
AcousticTransfer
Operating loads Operating loads
Break the system at the points where the forces enter the body (Receiver)
Total Acoustic Response is summation of partial responses over all noise paths
Pt = ΣΣΣΣ paths [Pi ] = ΣΣΣΣ paths [ (P/F) i * Fi ]
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 65
Identifying Key NVH PathsTPA Example: Contribution at One Transfer Path
Partial response from a particular path: Pi = (P/F) i * Fi
P/T LoadCrank torque
91 Hz
FiTFi
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 66
Identifying Key NVH PathsTPA Example: Sum of Key Transfer Paths at One Peak
P/T LoadCrank torque
P/T LoadCrank torque
Total Response: Pt = ΣΣΣΣ paths [Pi ] = ΣΣΣΣ paths [ (P/F) i * Fi ]
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 67
Attenuating Key NVH PathsTPA Example: Identifying Root Cause of Dominant Paths
P/T LoadCrank torque
PMiFi
TFi
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 68
Attenuating Key NVH PathsTPA Example: Dominant Paths over Frequencies
P/T LoadCrank torque
Fi
TFi
PMi
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 69
Designing Noise PathsTPA Example: Cascading Vehicle Targets to Subsystems
Limit TF to a 55 dB target
See changes in response
P/T LoadCrank torque
TFi
Once the dominant noise paths and root cause have been identified, the task is reduced to solving problems of:
1. High Force2. High Transfer Function3. High Point Mobility
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 70
Designing Noise Paths
Fi
Acoustic Transfer (P/F)iAcoustic Transfer (P/F)i
Operating loads createForces (Fi) into body atAll noise paths
F FF F
FF F
Pt = ΣΣΣΣ paths [Pi ] = ΣΣΣΣ paths [ Fi * (P/F) i ] = ΣΣΣΣ paths [ Fi * (P/V) i * (V/F)i]
P/V
P/F(Kbody)
V/F
Measurement Parameters Generic Targets
P/F Acoustic Sensitivity 50 - 60 dBL/N
V/F Structural Point Mobility (Receiver Side)
0.2 to 0.3 mm/sec/N
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 71
Recall for Acoustic Response Pt
Pt = ΣΣΣΣ paths [Pi ] = ΣΣΣΣ paths [ Fi * (P/V) i * (V/F)i]
“Downstream” Effects: Body Panels
(P/V)i !!!! �Downstream� (Body Panel) System Dynamics: Three Main Effects:
Increased Damping
Increased Stiffness
1. Panel Damping
2. Panel Stiffness
3. Panel Acoustic Contribution
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 72
Generic Noise Path Targets
K iso
K body> 5.0
K iso
K source
> 20.0
AcousticSensitivity < 50 - 60
dBL/N
StructuralMobility < 0.2 to 0.3 mm/sec/N
Panel Damping Loss Factor> .10
Primary: Minimize the Source Force< 1.0 N
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 73
Final Remarks on Mid Frequency Analysis
• Effective isolation at dominant noise paths is critical• Effective isolation at dominant noise paths is critical
• Reduced mobilities at body & source and softenedbushing are key for effective isolation
• Reduced mobilities at body & source and softenedbushing are key for effective isolation
• Other means of dealing with high levels of response(Tuned dampers, damping treatments, isolatorplacement at nodal locations) are also effective
• Other means of dealing with high levels of response(Tuned dampers, damping treatments, isolatorplacement at nodal locations) are also effective
• Mode Separation remains a valid strategy as modesin the source structure start to participate
• Mode Separation remains a valid strategy as modesin the source structure start to participate
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 74
Structure Borne NVH: Concepts Summary
• Source-Path-Receiver as a system1. Reduce Source
2. Rank and Manage Paths
3. Consider Subjective Response
• Effective Isolation
• Mode Management
• Nodal Point Placement
• Attachment Stiffness
• �Downstream� (Body Panel) Considerations
• Source-Path-Receiver as a system1. Reduce Source
2. Rank and Manage Paths
3. Consider Subjective Response
• Effective Isolation
• Mode Management
• Nodal Point Placement
• Attachment Stiffness
• �Downstream� (Body Panel) Considerations
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 75
Structure Borne NVH Workshop• Introduction• Low Frequency Basics• Mid Frequency Basics• Live Noise Attenuation Demo• New Technology
Uncertainty and NVH Scatter• Closing Remarks
Greg Goetchius
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.Duncan
Toolbox Demo Noise Test Results
85
61
68
63
55
47
39
30
40
50
60
70
80
90
1) Baseline:Imbalance, No
Isolation
2) Imbalance +Isolation
3) No Imbalance,No Isolation
4) No Imbalance,No Isolation +
Damping
5) No Imbalance +Isolation +Damping
6) #5 + Absorption 7) #6 + InsulatorMat
SPL
(dB
A)
Tool Box Demo Test Results
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 77
Structure Borne NVH Workshop• Introduction• Low Frequency Basics• Mid Frequency Basics• Live Noise Attenuation Demo• New Technology
NVH Scatter and UncertaintyClosing Remarks Alan Duncan
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 78
NVH Scatter and Uncertainty
• Scatter 20 Years Ago
• Scatter 10 Years Ago
• New Technology to Address Scatter
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 79
NVH Scatter and Uncertainty
• Scatter 20 Years Ago
• Scatter 10 Years Ago
• New Technology to Address Scatter
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 80
Frequency ( Hz )
Mag
. of F
RF
Magnitude of 99 Structure Borne Noise Transfer Functions for Rodeo�s at the Driver MicrophoneMeasurements from Kompella and Bernhard ( Ref. 8 ) 1993 Society of Automotive Engineers, Inc.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 81
Soun
d Pr
essu
re [
dB( l
in)]
Frequency ( Hz )
Acoustic Scatter from Simulation of the vibroacoustic behavior of a vehicle due to possible tolerances in the component area and in the production process.
© 2000 Society of Automotive Engineers, Inc.Reproduced with permission from paperby Freymann, et. Al. (Ref. 9)
12 dB Variation
Experimentally detected Scatter in low frequency vibroacoustic behavior of production vehicles.
Freymann, BMW NVH Scatter Results
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 82
CONCLUSIONs: From K/B and BMW StudiesIt is not highly probable:
1. that a Single Test will represent the Mean response2. that a CAE Simulation will match a Single Test
Variability observed from multiple tests of �identical� vehicles is important in understanding the degree to which the Test (or Simulation) of a Design is representative of the Mean response.How many Tests (or Simulations) of a Design would be required for the result to be considered statistically significant?
Scatter Implications for Test (or Simulation) NVH Development
Scatter is the �Physics�
Test Simulation
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 83
NVH Scatter and Uncertainty
• Scatter 20 Years Ago
• Scatter 10 Years Ago
• New Technology to Address Scatter
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 84
Test Variation Band10. dB; 50-150 Hz20. dB; 150-500 Hz
Reference Baseline Confidence CriterionFor Operating Response Simulations
Test Upper BoundTest Band AverageTest Lower Bound
REF. 8
Confidence Criterion:Simulation result mustfall within the band oftest variation.
Simulation Prediction
FUDGEFACTORS
Soun
d FR
F
Frequency Hz2003 Workshop Confidence Criterion Lecture with Voice Track available at www.AutoAnalytics.com on DOWNLOAD page.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 85
FlashBack: 1995 Paper on Root Cause of Scatter
(Ref. 15)
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 86
Root Cause of Scatter : Conditions
Total Response
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 87
NVH Scatter and Uncertainty
• Scatter 20 Years Ago
• Scatter 10 Years Ago
• New Technology to Address Scatter
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 88(Ref. 12)
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
Goal: Define a Modeling Methodology that:1. Accounts for NVH Scatter2. Quantifies Uncertainty with Statistical
Significance using a Stochastic Model3. Accounts for the Combined Effect of Modeling
and Manufacturing Uncertainty
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 89
(See Ref. 11 for Model Details)
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
Tactile Responses
POWERTRAIN LOADS
NTF @ DRIVER EAR
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 90
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
Standard Eqn. forStructural-Acoustic Coupling Modal Model
Typical Derivation for creating the randomized Dynamic Matrix with Gaussian Distribution.Non-Parametric: Direct Changes in Modal Matrices.
The scatter created is a function of:Dispersion Parameter: δOnce determined, δ is a constant controlling the amplitude level of scatter.
7 Dispersion Constants are needed:
3 for Structure: M, D, K
3 for Acoustics: M, D, K
1 for Coupling: Cn,m
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 91
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
Proof of Process ConvergenceCONCLUSIONS: Converged at 200 REALIZATIONS
and with Struct to 400 and Fluid to 350 Hz
Monte Carlo Randomization
Converges at 200 Realizations of the Random Matrices.
Increasing No. of Modes
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 92
Structural Uncertainty
Coupling Uncertainty
Acoustic Uncertainty
95% Upper Confidence BandNominal / Original Model Response50% Confidence Band (Mean Stochastic Model)95% Lower Confidence Band
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
CONCLUSION: � The Model shows 95% Confidence Bands with increasing Scatter at higher frequency similar to K-B Study.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 93(Ref. 13)
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
Main Paper - Development is ExtensiveIncludes Test Data Comparison
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 94
FIG. 10. Finite element mesh of the computational structural acoustic model.
(See Ref. 11 for Model Details)
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
Full Vehicle System � Body and ChassisStructural-Acoustic ModelSimilar Detail Level as first paper
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 95
FIG. 16. Comparisons of the stochastic computational model results with the experiments. Graphs of the root mean square of the acoustic pressures averaged in the cavity in dB scale: experiments for the 30 configurations (gray lines); Mean computational model (dashed line); mean value of the random response (mid thin solid line); 95% confidence region: the upper and lower envelopes are the upper and lower thick solid lines.
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
95% UPRNominal 50% Mean95% LWR
NOTE: Acoustic Dispersion Parameters are determined here with Mean Structure held Invariant.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 96
FIG. 19. Comparisons of the stochastic computational model results with the experiments for observation Obs6. Graphs of the moduli of the FRFs in dB scale: experiments for the 20 cars (gray lines); Mean computational model (dashed line); mean value of the random response (mid thin solid line); confidence region: the upper and lower envelopes are the upper and lower thick solid lines.
OBS # 6
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
P/T Load2nd Order
95% UPRNominal 50% Mean95% LWR
NOTE: Structure Dispersion Parameters are determined here with Mean Acoustic held Invariant.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 97
FIG. 20. Comparisons of the stochastic computational model results with the experiments for the booming noise. Graphs of the moduli of the FRFs in dB(A) scale: experiments for the 20 cars (thin gray lines); mean value of the experiments (thick gray line); Mean computational model (dashed line); Mean value of the random response (mid thin solid line); 95% confidence region: the upper and lower envelopes are the upper and lower thick solid lines.
P/T Load2nd Order
95% UprNominal 50% Mean95% Lwr
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 98
FIG. 20. Comparisons of the stochastic computational model results with the experiments for the booming noise. Graphs of the moduli of the FRFs in dB(A) scale: experiments for the 20 cars (thin gray lines); mean value of the experiments (thick gray line); Mean computational model (dashed line); Mean value of the random response (mid thin solid line); 95% confidence region: the upper and lower envelopes are the upper and lower thick solid lines.
P/T Load2nd Order
95% UprNominal 50% Mean95% Lwr
Non-Parametric Probabilistic Simulation; Soize, Durand, Gagliardini
CONCLUSIONS:. The 95% Confidence Bands encapsulate the Measured Scatter of 20 Vehicles.. Half-Bandwidth Scatter (between Mean and Upr 95%) is similar to K-B Half-Bands.
NOTE: The Method has Quantified the Model and Manufacturing Combined Uncertainty.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 99
(Ref. 14)
Non-Parametric Probabilistic Simulation; Jund, Guillaume, Gagliardini
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 100
FIG. 4: Computed booming noise inside a car vs. rpm, using only structure-borne excitation compared with the measured value (brown bold). Thin dotted black: deterministic computation; green: median value; thin dotted blue: lower bound with a 95% probability; dotted red: upper bound with a 95% probability.
P/T Load2nd Order
Non-Parametric Probabilistic Simulation; Jund, Guillaume, Gagliardini
95% UprNominal 50% Mean95% Lwr
TestMeasurement
Author:Focus of Correlation Effort
All Test Peaks in Band: Results imply a Countermeasure is needed.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 101
FIG. 7: Booming noise inside a car vs rpm. Stochastic modelling. Comparison of the median value of a baseline configuration (green) with a modification set (blue bold)
P/T Load2nd Order
Non-Parametric Probabilistic Simulation; Jund, Guillaume, Gagliardini
FIG. 6: Booming noise inside a car vs rpm. Deterministic models. Comparison of a baseline configuration (green) with a modification set (blue bold).
DETERMISTIC MODEL STOCHASTIC MODEL - Mean Level
. Amplitude Range = 30 dB
. Need Tradeoff Judgment
. Amplitude Range = 15 dB
. Decision is Clearer that both Designs are Equal Performers
Blue: New DesignGreen: Base
A-B Design Decision using Deterministic Model - vs - Mean Stochastic Model
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 102
Conclusions:
Kompella and Bernhard Test Observations are still relevant after 20 Years.
Scatter-like NVH Variation exists even in Best-in-Class vehicles.
Observations about Scatter:
Observations from Soize, Durand, Gagliardini, et. al. PapersThe Non-Parametric stochastic computational model with dispersion
parameters derived from a test database accounts for NVH Scatter due to combined Modeling and Manufacturing Uncertainties.
The Upper, Lower, and Mean Confidence Probabilities lead to moreprecise assessment of the effects of NVH scatter.
A database of dispersion parameters enables a virtual product development process assuring robust NVH performance.
The model configuration lends itself to an automated computational methodology driving a robust virtual product development process.
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 103
Structure Borne NVH Workshop• Introduction• Low Frequency Basics• Mid Frequency Basics• Live Noise Attenuation Demo• New Technology
Uncertainty and NVH Scatter• Closing Remarks: Q & A
Alan-Greg-Jimi
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 104
SAE 2013 NVH ConferenceStructure Borne NVH Workshop
Thank You for Your Time!
Q & AQ & A
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 105
Primary References (Workshop Basis: 4 Papers)
1. A. E. Duncan, et. al., “Understanding NVH Basics”, IBEC, 1996
2. A. E. Duncan, et. al., “MSC/NVH_Manager Helps Chrysler Make Quieter Vibration-free Vehicles”, Chrysler PR Article, March 1998.
3. B. Dong, et. al., “Process to Achieve NVH Goals: Subsystem Targets via ‘Digital Prototype’ Simulations”, SAE 1999-01-1692, NVH Conference Proceedings, May 1999.
4. S. D. Gogate, et. al., “’Digital Prototype’ Simulations to Achieve Vehicle Level NVH Targets in the Presence of Uncertainties’”,
SAE 2001-01-1529, NVH Conference Proceedings, May 2001
Structure Borne NVH References
WS + Refs. at www.AutoAnalytics.com at download link
Structure Borne NVH Workshop - on InternetAt SAE www.sae.org/events/nvc/specialevents.htm
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 106
Supplemental Reference Recommendations5. T.D. Gillespie, Fundamentals of Vehicle Dynamics, SAE 1992
(Also see SAE Video Lectures Series, same topic and author)6. D. E. Cole, Elementary Vehicle Dynamics, Dept. of Mechanical
Engineering, University of Michigan, Ann Arbor, Michigan, Sept. 1972
7. J. Y. Wong, Theory of Ground Vehicles, John Wiley & Sons, New York, 1978
8. N. Takata, et.al. (1986), “An Analysis of Ride Harshness” Int. Journal of Vehicle Design, Special Issue on Vehicle Safety, pp. 291-303.
9. T. Ushijima, et.al. “Objective Harshness Evaluation” SAE Paper No. 951374, (1995).
10. G. Goetchius; �The Seven Immutable Laws of CAE/Test Correlation� Sound and Vibration Mag. Editorial June 2007, online at SandV.com
Structure Borne NVH References
2013 SAE NVC Structure Borne Noise Workshop2013 Automotive Analytics LLC A.E.DuncanSlide 107
New Technology References (2013 NVH Workshop)
11. Sol, A.; Van Herpe, F.; “Numerical Prediction of a Whole Car Vibro-Acoustic Behavior at Low Frequencies”; SAE # 2001-01-1521
12. Durand, J.; Gagliardini, L.; Soize, C.; “Nonparametric Modeling of the Variability of Vehicle Vibroacoustic Behavior”; SAE # 2005-01-2385; SAE 2005 Noise and Vibration Conference Proceedings.
13. Durand, J.; Gagliardini, L.; Soize, C.; “Structural-acoustic modeling of automotive vehicles in presence of uncertainties and experimental identification and validation”; Journal of the Acoustical Society of America 24, p 1513-1525
14. Jund, A.; Gagliardini, L.; et.al.; “AN INDUSTRIAL IMPLEMENTATION OF NON-PARAMETRIC STOCHASTIC MODELLING OF VEHICLE VIBROACOUSTIC RESPONSE” CONVEBONOV Workshop, University of Sussex, Brighton, UK, March 27-28 2012
15. Gardhagen, B. and Plunt, J., “Variation of Vehicle NVH Properties due to Component Eigenfrequency Shifting - Basic Limits of Predictability” SAE 951302 May 1995 NVH Conference
Structure Borne NVH References