7. Structure Borne Noise and Vibration
Vibrating
Source
Frequency Range: up to 1000 Hz
System Characterization
• Source of Excitation
• Transmission through Structural Paths
• “Felt” as Vibration
• “Heard” as Noise
Slide 7
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
8. Automotive NVH Frequency Range
Structure Borne Noise
Airborne Noise
Response
Absorption
+
Mass
+
Local Stiffness Sealing
+ +
Global Stiffness Damping Damping
“Low” “Mid” “High”
~ 150 Hz ~ 1000 Hz ~ 10,000 Hz
Log Frequency Slide 8
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
13. Low Frequency Basics
• Source-Path-Receiver Concept
• Single DOF System Vibration
• NVH Source Considerations
• Receiver Considerations
• Vibration Attenuation Strategies
Provide Improved Isolation
Mode Management
Nodal Point Mounting
Dynamic Absorbers
Slide 13
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
14. Single Degree of Freedom Vibration
APPLIED FORCE
F = FO sin 2 π f t
1 + (2ζ f fn ) 2
TR = FT / F =
(1 − f fn ) + (2ζ f fn )
2 2 2 2
m
Transmitted
Force
k c FT ζ = fraction of critical damping
fn = natural frequency k m
f = operating frequency
Slide 14
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
15. Vibration Isolation Principle
4
0.1
APPLIED FORCE
Transmissibility Ratio
0.15
F = FO sin 2 π f t
3
m TR = FT / F
0.25
2 k c FT Transmitted
0.375 Force
0.5
1.0
1
Isolation Region
Isolation Region
0
0 1 1.414 2 3 4 5
Frequency Ratio (f / fn) Slide 15
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
16. Low Frequency Basics
• Source-Path-Receiver Concept
• Single DOF System Vibration
• NVH Source Considerations
• Receiver Considerations
• Vibration Attenuation Strategies
Provide Improved Isolation
Mode Management
Nodal Point Mounting
Dynamic Absorbers
Slide 16
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
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.
Slide 20
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
21. Low Frequency Basics
• Source-Path-Receiver Concept
• Single DOF System Vibration
• NVH Source Considerations
• Receiver Considerations
• Vibration Attenuation Strategies
Provide Improved Isolation
Mode Management
Nodal Point Mounting
Dynamic Absorbers
Slide 21
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
22. Receiver Considerations
Subjective to Objective Conversions
Subjective NVH Ratings are typically based on a
10 Point Scale resulting from Ride Testing
Receiver Sensitivity is a Key Consideration
A 2 ≈ 1/2 A 1
Represents 1.0 Rating Change
TACTILE: 50% reduction in motion
SOUND : 6.dB reduction in sound pressure level
( long standing rule of thumb ) Slide 22
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
23. Low Frequency Basics
• Source-Path-Receiver Concept
• Single DOF System Vibration
• NVH Source Considerations
• Receiver Considerations
• Vibration Attenuation Strategies
Provide Improved Isolation
Mode Management
Nodal Point Mounting
Dynamic Absorbers
Slide 23
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
24. Symbolic Model of Unibody Passenger Car
8 Degrees of Freedom
2 4
8
1 3 5
6 7
Total 2178.2 Kg (4800LBS) Tires 350.3 N/mm
Mass Sprung 1996.7 Kg KF 43.8 N/mm
Unsprung 181.5 Kg (8.33% of Total) KR 63.1 N /mm
Powertrain 181.5 Kg Beam mass lumped on
grids like a beam
M2,3,4 =2 * M1,5
Slide 24
From Reference 6
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
25. 8 Degree of Freedom Vehicle NVH Model
Engine Mass
8
Engine Flexible Beam for Body
Isolator
1 2 3 4 5
Suspension
Springs
6 7
Wheels
Tires
Slide 25
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
26. 8 Degree of Freedom Vehicle NVH Model
Force Applied to Powertrain Assembly
Feng
8
1 2 3 4 5
6 7
Forces at Powertrain could represent a First Order
Rotating Imbalance
Slide 26
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
27. Engine Isolation Example
Response at M id Car
1.0000
Constant Force Load; F~A 15.9 Hz
8.5 Hz
Velocity (mm/sec)
0.1000
7.0 Hz
0.0100
0.0010
2 4
8
1 3 5
6 7
700 Min. RPM First Order Unbalance
0.0001 Operation Range of Interest
5.0 10.0 15.0 20.0
Frequency Hz
Slide 27
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
28. Concepts for Increased Isolation
“Double” isolation is the typical strategy for
further improving isolation of a given vehicle
design.
Second Level of
Isolation is at Subframe
to Body Mount
Subframe is
Intermediate Structure
Suspension Bushing is first level
Slide 28
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
30. Double Isolation Example
Vertical Response at DOF3
6.0E+00
Base Model
5.0E+00
(mm/sec)
Without Double_ISO
4.0E+00
2 4
8
1 3 5
6 7
3.0E+00
Velocity
1.414*fn
2.0E+00
1.0E+00
0.0E+00
5.0 10.0 15.0 20.0
Frequency Hz
Slide 30
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
31. Low Frequency Basics
• Source-Path-Receiver Concept
• Single DOF System Vibration
• NVH Source Considerations
• Receiver Considerations
• Vibration Attenuation Strategies
Provide Improved Isolation
Mode Management
Nodal Point Mounting
Dynamic Absorbers
Slide 31
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
32. Mode Management Chart
EXCITATION SOURCES
Inherent Excitations (General Road Spectrum, Reciprocating Unbalance, Gas Torque, etc.)
Process Variation Excitations (Engine, Driveline, Accessory, Wheel/Tire Unbalances)
0 5 10 15 20 25 30 35 40 45 50
First Order Wheel/Tire Unbalance Hz
V8 Idle
Hot - Cold
CHASSIS/POWERTRAIN MODES
Suspension Hop and Tramp Modes
Ride Modes Suspension Longitudinal Modes
Powertrain Modes Exhaust Modes
0 5 10 15 20 25 30 35 40 45 50
Hz
BODY/ACOUSTIC MODES
Body First Torsion Steering Column First Vertical Bending
Body First Bending First Acoustic Mode
0 5 10 15 20 25 30 35 40 45 50
Hz
(See Ref. 1) Slide 32
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
33. 8 Degree of Freedom Vehicle NVH Model
Bending Mode Frequency Separation
8
1 2 3 4 5
Beam Stiffness was
adjusted to align Bending
Frequency with Suspension
6 7
Modes and then
progressively separated
back to Baseline.
Slide 33
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
35. Low Frequency Basics
• Source-Path-Receiver Concept
• Single DOF System Vibration
• NVH Source Considerations
• Receiver Considerations
• Vibration Attenuation Strategies
Provide Improved Isolation
Mode Management
Nodal Point Mounting
Dynamic Absorbers
Slide 35
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
36. Mount at Nodal Point
First Bending: Nodal Point Mounting Example
Front input forces Rear input forces
Locate wheel centers at node points of the first bending modeshape
to prevent excitation coming from suspension input motion.
Slide 36
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
37. Mount at Nodal Point
First Torsion: Nodal Point Mounting Examples
Side View
Rear View
Passenger sits at Engine
node point for
First Torsion.
Transmission Mount of a
3 Mount N-S P/T is near
the Torsion Node. Slide 37
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
38. Powertrain Bending Mode Nodal Mounting
1 2 3 4 5
6 7
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.
Slide 38
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
39. 8 Degree of Freedom Vehicle NVH Model
Bending Node Alignment with Wheel Centers
Redistribute Beam Masses
8 to move Node Points to
Align with points 2 and 4
1 2 3 4 5
6 7
Slide 39
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
40. First Bending Nodal Point Alignment
Response at Mid-Car
4.0E+00
Node Shifted
4
Base Model 8
2
(m m /sec)
1 3 5
6 7
3.0E+00
2.0E+00
Velocity
1.0E+00
0.0E+00
5.0 10.0 15.0 20.0
Frequency Hz
Slide 40
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
41. Low Frequency Basics
• Source-Path-Receiver Concept
• Single DOF System Vibration
• NVH Source Considerations
• Receiver Considerations
• Vibration Attenuation Strategies
Provide Improved Isolation
Mode Management
Nodal Point Mounting
Dynamic Absorbers
Slide 41
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
42. Dynamic Absorber Concept
Auxiliary Spring-Mass-Damper
m = M / 10
x x
SDOF 2DOF
M M
YO YO
Slide 42
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
43. Powertrain Example of Dynamic Absorber
Anti-Node Identified
at end of Powerplant
k c
m
Absorber attached at anti-node acting in
the Vertical and Lateral plane.
Tuning Frequency = √ k/m
Slide 43
[Figure Courtesy of DaimlerChrysler Corporation]
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
45. Low Frequency Basics - Review
• Source-Path-Receiver Concept
• Single DOF System Vibration
• NVH Source Considerations
• Receiver Considerations
• Vibration Attenuation Strategies
Provide Improved Isolation
Mode Management
Nodal Point Mounting
Dynamic Absorbers
Slide 45
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
46. Structure Borne NVH Workshop
• Introduction
• Low Frequency Basics
• Mid Frequency Basics Alan Duncan
• Live Noise Attenuation Demo
• Case Studies
• Interior Noise Diagnosis using VINS
• NVH Principles: Applications
• Closing Remarks
Slide 46
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
47. Mid Frequency NVH Fundamentals
This looks familiar!
Frequency Range of Interest has changed to
150 Hz to 1000 Hz Slide 47
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
48. Typical NVH Pathways to the Passenger
PATHS
FOR
STRUCTURE
Noise Paths are the
BORNE
Noise Paths are the
same as Low
same as Low NVH
Frequency Region
Frequency Region Slide 48
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
49. Mid-Frequency Analysis Character
Structure Borne Noise
Airborne Noise
• Mode separation is less practical in
• Mode separation is less practical in
High modal density mid-frequency
mid-frequency
and coupling in
source, path and
• New Strategy is Effective Isolation:
• New Strategy is Effective Isolation:
receiver
Achieved by reducing energy transfer
Achieved by reducing energy transfer
locally between source and receiver at
locally between source and receiver at
key paths.
key paths.
Response
Absorption
+
Local Stiffness Mass
+ +
Global Stiffness Damping Sealing
“Low” “Mid” “High”
~ 150 Hz ~ 1000 Hz
Log Frequency ~ 10,000 Hz
Slide 49
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
50. Mid-Frequency Analysis Character
Control Measures for Mid Frequency Concerns
Effective Isolation
Attenuation along Key Noise Paths
Slide 50
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
51. Mid-Frequency Analysis Character
Control Measures for Mid Frequency Concerns
Effective Isolation
Attenuation along Key Noise Paths
Slide 51
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
52. Isolation Effectiveness
Classical SDOF: Rigid
Source and Receiver
“Real Structure”
1.0 Flexible (Mobile)
Source and
Transmissibility Ratio
Receiver
Isolation Region
Isolation Region f/fn
1.0 1.414 10.0
Effectiveness deviates from the classical development as resonances
occur in the receiver structure and in the foundation of the source.
Slide 52
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
53. Mobility
• Mobility is the ratio of velocity response at the excitation point on structure
to the force applied in the direction of the velocity
Velocity
Mobility =
Force
• Mobility, also called Admittance, characterizes Dynamic Stiffness of
the structure at load application point
Frequency * Displacement
Mobility =
Force
Frequency
=
Dynamic Stiffness
Slide 53
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
54. Isolation
• The isolation effectiveness can be quantified by a theoretical model based on
analysis of the SOURCE - PATH - RECEIVER transfer across an isolator
• Transmissibility Ratio (TR) is used to objectively define measure of isolation
Force from source with isolator
TR =
Force from source without isolator
V Receiver Vr
V Receiver Vr
V Fr
Fr Fs =
Yi + Y r + Y s F ir
V ir
Fs
Vs Isolator V is
Source
F is
V
F s= Fs
Yr +Ys Vs
Source
Slide 54
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
55. Isolation
Force from source with an isolator Receiver Vm
TR =
Force from source without an isolator
Fm
TR = ( Y r + Y s ) / ( Y i + Y r + Y s ) F im
V im
Isolator V if
Y r : Receiver mobility
F if
Y i : Isolator mobility
Y s : Source mobility Ff
Vf
Source
• For Effective Isolation (Low TR) the Isolator
Mobility must exceed the sum of the Source and
Receiver Mobilities.
Recall that Y ∝1
K Slide 55
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
56. Designing Noise Paths
1 1 1 1 1
TR = ( + ) / ( + + )
K body K source K body K iso K source
K source
K body K iso
K iso 1.0 5.0 20.0
1.0 0.67 0.55 0.51
5.0 0.55 0.29 0.20
20.0 0.51 0.20 0.09
Generic targets:
body to bushing stiffness ratio of at least 5.0
source to bushing stiffness ratio of at least 20.0
Slide 56
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
57. Body-to-Bushing Stiffness Ratio
Relationship to Transmissibility
0.6
For a source ratio of 20
Transmissibility Ratio TR
0.5
0.4
Target Min. = 5
0.3
gives TR = .20
0.2
0.1
0
1 2 3 4 5 6 7 8 9 10
Stiffness Ratio; K body / K iso
Slide 57
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
58. Mid-Frequency Analysis Character
Control Measures for Mid Frequency Concerns
Effective Isolation
Attenuation along Key Noise Paths
Slide 58
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
59. Identifying Key NVH Paths
Key NVH paths are identified by Transfer Path Analysis (TPA)
Acoustic
Acoustic
Transfer
Transfer
Fi Break the system at the
points where the forces
enter the body (Receiver)
Operating loads Operating loads
Total Acoustic Response is summation of partial responses
over all noise paths
Pt = Σ paths [Pi ] = Σ paths [ (P/F) i * Fi ]
Slide 59
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
60. Designing Noise Paths
P/V Acoustic Transfer (P/F)i
Acoustic Transfer (P/F)i
P/F
V/F
F F (Kbody) F F
F F Fi F
Operating loads create
Forces (Fi) into body at
All noise paths
Pt = Σ paths [Pi ] = Σ paths [ Fi * (P/F) i ]
= Σ paths [ Fi * (P/V) i * (V/F) i ]
Measurement Parameters Generic Targets
P/F Acoustic Sensitivity 50 - 60 dBL/N
V/F Structural Point Mobility 0.2 to 0.3
(Receiver Side) mm/sec/N Slide 60
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
62. Generic Noise Path Targets
K body K source
> 5.0 > 20.0
K iso K iso
Structural
Mobility < 0.2 to 0.3 mm/sec/N
Acoustic 50 - 60
<
Sensitivity dBL/N
Primary: Minimize the Source Force
< 1.0 N
Panel Damping Loss Factor
> .10
Slide 62
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
63. Final Remarks on Mid Frequency Analysis
• Effective isolation at dominant noise paths is critical
• Reduced mobilities at body & source and softened
bushing are key for effective isolation
• Mode Separation remains a valid strategy as modes
in the source structure start to participate
• Other means of dealing with high levels of response
(Tuned dampers, damping treatments, isolator
placement at nodal locations) are also effective
Slide 63
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
64. Structure Borne NVH Workshop
• Introduction
• Low Frequency Basics
• Mid Frequency Basics
• Live Noise Attenuation Demo
• Case Studies Greg Goetchius
• Interior Noise Diagnosis using VINS
• NVH Principles: Applications
• Closing Remarks
Slide 64
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
65. Tool Box Demo Test Results
Toolbox Demo Noise Test Results
90
85
80
70 68
SPL (dBA)
63
61
60
55
50 47
40 39
30
1) Baseline: 2) Imbalance + 3) No Imbalance, 4) No Imbalance, 5) No Imbalance + 6) #5 + Absorption 7) #6 + Insulator
Imbalance, No Isolation No Isolation No Isolation + Isolation + Mat
Isolation Damping Damping
Slide 65
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
66. Structure Borne NVH Workshop
• Introduction
• Low Frequency Basics
• Mid Frequency Basics
• Live Noise Attenuation Demo
• Case Studies Kiran Govindswamy
• Interior Noise Diagnosis using VINS
• NVH Principles: Applications
• Closing Remarks
Slide 66
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
67. “Time Domain” Transfer Path Analysis
VINS (Vehicle Interior Noise Simulation)
Excitation Transfer Behaviour Interior Noise
Airborne
Loudspeaker Noise Share
Airborne Path
Microphones
FEV FEV
Overall
Power Train Noise Interior Noise
Intake&Exhaust Noise
...
Engine Mount Vehicle
Structure-Borne Path
Pi
Power Train Vibration
Drive Line Vibration Structureborne
Overall Vehicle Transfer Function
... Noise Share
Slide 67
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
68. “Time Domain” Transfer Path Analysis
VINS (Vehicle Interior Noise Simulation)
Overall Structure-Borne Sound Transmission
Resultant Dynamic Mount Stiffness
ae ab Fb
Mount Apparent Mass Vehicle Body
Engine Excitation Transmissibility of Body
Test Bench Impact Test
abody Fbody Pinterior
aengine = Pinterior
aengine abody Fbody
Resultant Dynamic Mount
Stiffness
Slide 68
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
73. “Time Domain” Transfer Path Analysis
VINS: Application to “Transient Diesel Clatter”
Mic. left Mic. right Mic. top Mic. bottom Mic. front Mic. rear Intake orif. Exhaust tp.
Left mnt. Right mnt. RR A RR B Trans.
link
Slide 73
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
74. HEV, PHEV, ReEV, and EV NVH
Coasting G D C
Constant D C D C
G
speeds
A D
Acceleration B F
A D D
Drive-away C
B F
Start & A C F A F D
idle B E B G
Red light
E A
(Stop)
ICE ICE Start/Stop Regeneration Power AER
stopped idling ICE Batt. Charging Assist
• A: Global powertrain vibration B: Driveline vibration
• C: Noise of HEV specific components D: Magnetic noise E-Motor/(Generator)
• E: Noise of accessories F: Gearbox rattle noise due to
• G: Noise pattern changeover ICE (non-uniformity) and E-Motor
Slide 74
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
75. Structure Borne NVH Workshop
• Introduction
• Low Frequency Basics
• Mid Frequency Basics
• Live Noise Attenuation Demo
• Case Studies
• Interior Noise Diagnosis using VINS
• NVH Principles: Applications
Jianmin Guan
• Closing Remarks
Slide 75
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
87. SAE 2011 NVH Conference
Structure Borne NVH Workshop
Thank You for Your Time!
Q&A
Slide 87
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
88. Structure Borne NVH References
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 Workshop - on Internet
At SAE www.sae.org/events/nvc/specialevents.htm
Slide 88
WS + Refs. at www.AutoAnalytics.com/papers.html
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com
89. Structure Borne NVH References
Supplemental Reference Recommendations
5. 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).
Slide 89
2011 SAE Structure Borne NVH Workshop www.autoanalytics.com