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Design For NVH

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Design For NVH MPD575 DFX Jonathan Weaver Development History Originally developed by Cohort 1 students: Jeff Dumler, Dave McCreadie, David Tao Revised by Cohort 1 ... – PowerPoint PPT presentation

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Title: Design For NVH


1
Design For NVH
  • MPD575 DFX
  • Jonathan Weaver

2
Development History
  • Originally developed by Cohort 1 students Jeff
    Dumler, Dave McCreadie, David Tao
  • Revised by Cohort 1 students T. Bertcher, L.
    Brod, P. Lee, M. Wehr
  • Revised by Cohort 2 students D. Gaines, E.
    Donabedian, R. Hall, E. Sheppard, J. Randazzo

3
Design For NVH (DFNVH)
  • Introduction to NVH
  • DFNVH Heuristics
  • DFNVH Process Flow and Target Cascade
  • DFNVH Design Process Fundamentals
  • Key DFNVH Principles
  • Airborne NVH
  • Radiated/Shell Noise
  • Tube Inlet/Outlet Noise
  • Impactive Noise
  • Air Impingement Noise
  • Structure-Borne NVH
  • Wind Noise Example
  • 2002 Mercury Mountaineer Case Study
  • Summary

4
Introduction to NVH What is NVH?
  • Movement is vibration, and vibration that reaches
    the passenger compartment in the right
    frequencies is noise.
  • The science of managing vibration frequencies in
    automobile design is called NVH - Noise,
    Vibration, and Harshness.
  • It is relatively easy to reduce noise and
    vibration by adding weight, but in an era when
    fuel economy demands are forcing designers to
    lighten the car, NVH engineers must try to make
    the same parts stiffer, quieter, and lighter.

5
Introduction to NVH What is NVH?
  • Noise
  • Typically denotes unwanted sound, hence
    treatments are normally to eliminate or reduce
  • Variations are detected by ear
  • Characterized by frequency, level quality
  • May be Undesirable (Airborne)
  • May be Desirable (Powerful Sounding Engine)

6
Introduction to NVH What is NVH?
  • Vibration
  • An oscillating motion about a reference point
    which occurs at some frequency or set of
    frequencies
  • Motion sensed by the body (structureborne)
  • mainly in 0.5 Hz - 50 Hz range
  • Characterized by frequency, level and direction
  • Customer Sensitivity Locations are steering
    column, seat track, toe board, and mirrors
    (visible vibrations)

7
Introduction to NVH What is NVH?
  • Harshness
  • Low-frequency (25 -100 Hz) vibration of the
    vehicle structure and/or components
  • Frequency range overlaps with vibration but human
    perception is different.
  • Perceived tactilely and/or audibly
  • Rough, grating or discordant sensation

8
Introduction to NVH What is NVH
  • Airborne Noise
  • Kind of sound most people think of as noise, and
    travels through gaseous mediums like air.
  • Some people classify human voice as airborne
    noise, but a better example is the hum of your
    computer, or air conditioner.
  • Detected by the human ear, and most likely
    impossible to detect with the sense of touch.
  • Treatment / Countermeasures Barriers or
    Absorbers

9
Introduction to NVH What is NVH?
  • Structureborne
  • Vibration that you predominately feel, like the
    deep booming bass sound from the car radio next
    to you at a stoplight.
  • These are typically low frequency vibrations that
    your ear may be able to hear, but you primarily
    feel
  • Treatment / Countermeasure Damping or Isolation

10
Introduction to NVH What is NVH?
  • Barriers
  • Performs a blocking function to the path of the
    airborne noise. Examples A closed door, backing
    on automotive carpet.
  • Barrier performance is strongly correlated to the
    openings or air gaps that exist after the barrier
    is employed. A partially open door is less
    effective barrier than a totally closed door.
  • Barrier performance is dependent on frequency,
    and is best used to treat high frequencies.
  • If no gaps exist when the barrier is employed,
    then weight becomes the dominant factor in
    comparing barriers.

11
Introduction to NVH What is NVH?
  • Barriers Design Parameters
  • Location (close to source)
  • Material (cost/weight)
  • Mass per Unit Area
  • Number and Thickness of Layers
  • Number and Size of Holes

12
Introduction to NVH What is NVH?
  • Absorbers
  • Reduces sound by absorbing the energy of the
    sound waves, and dissipating it as heat.
    Examples headliner, and hood insulator.
  • Typically, absorbers are ranked by the ability to
    absorb sound that otherwise would be reflected
    off its surface.
  • Good absorber designs contain complex geometries
    that trap sound waves, and prevent reflection
    back into the air.
  • Absorber performance varies with frequency.

13
Introduction to NVH What is NVH?
  • Absorbers Design Parameters
  • Area of absorbing material (large as possible)
  • Type of material (cost/weight)
  • Thickness (package/installation)

14
Introduction to NVH What is NVH?
  • Damping
  • Defined as a treatment of vibration to reduce the
    magnitude of targeted vibrations
  • Damping is important because it decreases the
    sensitivity of the body at resonant frequencies
  • Vehicle Sources of Damping are Mastics, sound
    deadening materials, weather-strips/seals, tuned
    dampers, and body/engine mounts

15
Introduction to NVH What is NVH?
  • Damping Design Parameters
  • Density (low as possible)
  • Stiffness (high as possible)
  • Thickness (damping increases with the square of
    thickness)
  • Free surface versus constrained layer
  • Constrained layer damping is more efficient than
    free surface damping on a weight and package
    basis, but is expensive, and raises assembly
    issues.
  • Note Temperature range of interest is very
    important because stiffness and damping
    properties are very temperature sensitive

16
Introduction to NVH What is NVH?
  • Isolation
  • Method of detaching or separating the vibration
    from another system or body.
  • By definition does nothing to reduce the
    magnitude of vibration, simply uncouples the
    vibration from the system you are protecting.
  • All isolation materials perform differently at
    different frequencies, and if engineered
    incorrectly, may make NVH problems worse instead
    of better.

17
Introduction to NVH What is NVH?
  • Isolation by Bushings and Mounts
  • Excitations are generally applied to components
    such as engine or road wheels.
  • The force to the body is the product of the
    mount stiffness and the mount deflection,
    therefore strongly dependent on the mount spring
    rates
  • Compliant (softer) mounts are usually desirable
    for NVH and ride, but are undesirable for
    handling, durability and packaging (more
    travel/displacement space required).
  • Typically, the isolation rates (body
    mount/engine mount stiffness) that are finally
    selected, is a result of the reconciliation
    (trade-off) of many factors.

18
Introduction to NVHWhy Design for NVH?
  • NVH is overwhelmingly important to customers.
    You never, ever get lucky with NVH. The
    difference between good cars and great cars is
    fanatical attention to detail.
  • Richard Parry-Jones, 11/99

19
Introduction to NVHWhy Design for NVH?
  • NVH impacts Customer Satisfaction
  • NVH impacts Warranty
  • NVH has financial impact

20
Introduction to NVHWhy Design for NVH?
Corporate Leverage vs. Customer Satisfaction NVH
Customer Satisfaction Needs Improvement at 3 MIS
9
IMPROVE
SUSTAIN / BUILD

Overall Handling
Relative Leverage
6.9
Cup holders

Exterior Styling

REVIEW
MAINTAIN
5
65
85
77
21
Introduction to NVHWhy Design for NVH?
NVH Can Both Dissatisfy and Delight
Customer Satisfaction
KANO Model
Exciting Quality (Surprise Delight)
Performance Quality (Attributes)
Sound Quality TGR
Harley Mustang Lexus
Loudness
Degree of Achievement
Performance
- Performance
Dissatisfiers
Basic Quality (Inhibitors)
Unusual Noises TGW
Axle Whine Wind Noise
- Customer Satisfaction
22
Introduction to NVHWhy Design for NVH?
Summary of Customer Importance
  • Customers place a high value on NVH performance
    in vehicles
  • About 1/3 of all Product / Quality Complaints are
    NVH-related

23
Introduction to NVHWhy Design for NVH?
Summary of Customer Importance (continued)
  • About 1/5 of all Warranty costs are NVH-related
  • Dealer may spend many hours to determine source
    of NVH problem
  • Dealer may have to repair or rebuild parts that
    have not lost function but have become source of
    NVH issue.
  • NVH can provide both dissatisfaction and delight

24
Design For NVH (DFNVH)
  • Introduction to NVH
  • DFNVH Heuristics
  • DFNVH Process Flow and Target Cascade
  • DFNVH Design Process Fundamentals
  • Key DFNVH Principles
  • Airborne NVH
  • Radiated/Shell Noise
  • Tube Inlet/Outlet Noise
  • Impactive Noise
  • Air Impingement Noise
  • Structure-Borne NVH
  • Wind Noise Example
  • 2002 Mercury Mountaineer Case Study
  • Summary

25
Design For NVH Heuristics
  • Design the structure with good "bones"
  • If the NVH problem is inherent to the
    architecture, it will be very difficult to
    tune it out.
  • To remain competitive, determine and control the
    keys to the architecture from the very beginning.
  • Set aggressive NVH targets, select the best
    possible architecture from the beginning, and
    stick with it (additional upfront NVH resources
    are valuable investments that will return a high
    yield)

26
Design For NVH Heuristics
  • Cost rules
  • Once the architecture is selected, it will be
    very costly to re-select another architecture.
    Therefore, any bad design will stay for a long
    time

27
Design For NVH Heuristics
  • Don't confuse the functioning of the parts for
    the functioning of the system (Jerry Olivieri,
    1992).
  • We need to follow Systems Engineering principles
    to design for NVH. Customers will see functions
    from the system, but sound designs requires our
    ability to develop requirements of the parts by
    cascading functional requirements from the system

28
Design For NVH (DFNVH)
  • Introduction to NVH
  • DFNVH Heuristics
  • DFNVH Process Flow and Target Cascade
  • DFNVH Design Process Fundamentals
  • Key DFNVH Principles
  • Airborne NVH
  • Radiated/Shell Noise
  • Tube Inlet/Outlet Noise
  • Impactive Noise
  • Air Impingement Noise
  • Structure-Borne NVH
  • Wind Noise Example
  • 2002 Mercury Mountaineer Case Study
  • Summary

29
DFNVH Process Flow and Target Cascade
  • During the early stages of a vehicle program,
    many design trade-offs must be made quickly
    without detailed information.
  • For example, on the basis of economics and
    timing, power plants (engines) which are known to
    be noisy are chosen. The program should realize
    that extra weight and cost will be required in
    the sound package. (Historical Data)
  • If a convertible is to be offered, it should be
    realized that a number of measures must be taken
    to stiffen the body in torsion, and most likely
    will include stiffening the rockers. (Program
    Assumptions)

30
DFNVH Process Flow and Target Cascade
31
DFNVH Process Flow and Target Cascade
Noise Reduction Strategy Targets are even set
for the noise reduction capability of the sound
package.
32
DFNVH Process Flow and Target Cascade
Systems Engineering V and PD Process Timing
33
DFNVH Process Flow and Target Cascade
34
DFNVH Process Flow and Target Cascade
NVH Functional Attribute
Sub -Attributes
Road
P/T
Wind
Brake
Comp. S.Q.
SR
Pass-by Noise (Reg.)
35
DFNVH Process Flow and Target Cascade
Convert attribute target strategy to objective
targets
36
DFNVH Process Flow and Target Cascade
Acceleration NVH Target Cascade
37
DFNVH Process Flow and Target Cascade
  • NVH Classification Parameters
  • Operating Condition (idle, acceleration, cruise
    on a rough road, braking)
  • Phenomenon (boom, shake, noise) this is strongly
    affected by the frequency of the noise and
    vibration.
  • Source (powertrain, road, wind ..etc)
  • Classifying NVH problems provides a guidance for
    design, for example, low frequency problems such
    as shake, historically, involves major structural
    components such as cross members and joints.

38
DFNVH Process Flow and Target Cascade

39
DFNVH Process Flow and Target Cascade
  • The customers experience of NVH problems
    involves two factors, 1) the vehicle operating
    conditions, such as braking or WOT, and 2) the
    very subjective responses such as boom, growl,
    and groan.
  • It is critical that objective and subjective
    ratings be correlated so the customer concerns
    can be directly related to objective measures.
    This requires subjective-objective correlation
    studies comparing customer ratings and objective
    vibration measurements.

40
DFNVH Process Flow and Target Cascade
41
DFNVH Process Flow and Target Cascade
  • Summary
  • Noise reduction targets should be set for
    important operating conditions such as WOT (wide
    open throttle).
  • Noise reduction targets must be set for the
    radiated sound from the various sources.
  • The sound package must be optimized for barrier
    transmissibility and interior absorption.
  • Classifying NVH problems provides guidance for
    design and a means to communication among
    engineers.

42
Design For NVH (DFNVH)
  • Introduction to NVH
  • DFNVH Heuristics
  • Process Flow and Target Cascade
  • DFNVH Design Process Fundamentals
  • Key DFNVH Principles
  • Airborne NVH
  • Radiated/Shell Noise
  • Tube Inlet/Outlet Noise
  • Impactive Noise
  • Air Impingement Noise
  • Structure-Borne NVH
  • Wind Noise Example
  • 2002 Mercury Mountaineer Case Study
  • Summary

43
DFNVH Process FundamentalsSource-Path-Responder
  • Engine Firing Pulses
  • Driveshaft Imbalance
  • Rough Road
  • Tire Imbalance
  • Speed Bump
  • Gear Meshing
  • Body-Shape Induced Vortices

Excitation Source Examples
44
DFNVH Process FundamentalsSource-Path-Responder
Sensitivity
Tendency of the path to transmit energy from the
source to the responder, commonly referred to as
the transfer function of the system
45
DFNVH Process FundamentalsSource-Path-Responder
  • Example Body Sensitivity
  • Tactile
  • Point mobility (v/F)
  • (Structural velocity induced by force)
  • Acoustic
  • Airborne (p/p)
  • (Airborne sound pressure induced by pressure
    waves)
  • Structureborne (p/F)
  • (Airborne sound pressure induced by force)

46
DFNVH Process FundamentalsSource-Path-Responder
Body Sensitivity Demonstration Point Mobility
Typical Point Mobility Spectrum for Compliant
Stiff Structures
More Compliant
Point Mobility (V/F)
Less Compliant
Frequency ( f )
140
50
47
DFNVH Process FundamentalsSource-Path-Responder
S/W Steering Wheel
48
DFNVH Process FundamentalsSource-Path-Responder
Powertrain Noise Model
49
DFNVH Process FundamentalsSource-Path-Responder
Road Noise Model
50
DFNVH Process FundamentalsSource-Path-Responder
Driveline Model
51
DFNVH Process FundamentalsSound Quality
What is Sound Quality?
  • Historically, Noise Control meant reducing sound
    level
  • Focus was on major contributors (P/T, Road, Wind
    Noise)
  • Sound has multiple attributes that affect
    customer perception
  • All vehicle sounds can influence customer
    satisfaction
  • (e.g., component Sound Quality)
  • Noise Control no longer means simply reducing dB
    levels

52
DFNVH Process FundamentalsSound Quality
Why Sound Quality?
  • Generally not tied to any warranty issue
  • Important to Customer Satisfaction
  • - Purchase experience (door closing)
  • - Ownership experience (powertrain/exhaust)
  • A strong indicator of vehicle craftsmanship
  • - Brand image (powertrain)

53
DFNVH Process FundamentalsSound Quality
The Sound Quality Process
  • 1. Measurement (recording)
  • 2. Subjective evaluation (listening studies)
  • Actual or surrogate customers
  • 3. Objective analysis
  • Sound quality Metrics
  • 4. Subjective/Objective correlation
  • 5. Component design for sound quality

54
DFNVH Process FundamentalsSound Quality
Binaural Acoustic Heads
Stereo Sound Recording representing sound wave
interaction w/ human torso
55
DFNVH Process FundamentalsSound Quality
Sound Quality Listening Room
Used for Customer Listening Clinics.
56
DFNVH Process FundamentalsSound Quality
Poor Sound Quality
Good Sound Quality
57
DFNVH Process FundamentalsSound Quality
Quantifying Door Closing Sound Quality
1. Sound Level (Loudness) 2. Frequency Content
(Sharpness) 3. Temporal Behavior
58
DFNVH Process FundamentalsSound Quality
What Makes A Good Door Closing Sound?
Good Sound Poor Sound Quiet
Loud Low Frequency High
Frequency (Solid) (Tinny, Cheap)
One Impact Rings On (Bell) No
Extraneous Noise Rattles, Chirps, etc.
59
DFNVH Process FundamentalsSound Quality
Example Qualifying Door Closing Sound Quality
Good
Bad
Frequency (Hz) (y-axis)
Time (sec.) (x-axis)
Level (dBa) (color)
60
DFNVH Process FundamentalsSound Quality
Design for Sound Quality Door Closing Example
Perceived Sound
Structure-borne
Airborne
Seal Trans Loss
Radiated Snd.
Latch Forces
Str. Compliance
Inertia
Spring Rates
Material
61
DFNVH Process FundamentalsSound Quality
Conclusions
  • Sound Quality is critical to Customer
    Satisfaction
  • Understand sound characteristics that govern
    perception
  • Upfront implementation is the biggest challenge
  • Use commodity approach to component sound quality
  • Generic targets, supplier awareness, bench tests

62
Design For NVH (DFNVH)
  • Introduction to NVH
  • DFNVH Heuristics
  • Process Flow and Target Cascade
  • DFNVH Design Process Fundamentals
  • Key DFNVH Principles
  • Airborne NVH
  • Radiated/Shell Noise
  • Tube Inlet/Outlet Noise
  • Impactive Noise
  • Air Impingement Noise
  • Structure-Borne NVH
  • Wind Noise Example
  • 2002 Mercury Mountaineer Case Study
  • Summary

63
NVH Design Principles
  • Dynamic System NVH Model
  • Source X Path Response
  • Always work on sources first
  • Reduce the level of ALL sources by using quiet
    commodities
  • Path is affected by system architecture. Need to
    select the best architecture in the early design
    phase.
  • Engineer the paths in each application to tailor
    the sound level
  • Only resort to tuning in the late stage of design

64
NVH Design Principles
Source
Path
Responder
Radiated/Shell Noise
Acoustic Attenuation
Acoustic Attenuation
Tube Inlet/Outlet Noise
Environment Sensitivity
Airborne NVH
Impactive Noise
Acoustic Attenuation
Acoustic Attenuation
Air Impingement Noise
Customer
Excitation Source, Energy Input
Structure-borne NVH
Structure Sensitivity
65
NVH Design Principles
Source
Path
Responder
Radiated/Shell Noise
Acoustic Attenuation
Acoustic Attenuation
Tube Inlet/Outlet Noise
Environment Sensitivity
Airborne NVH
Impactive Noise
Acoustic Attenuation
Acoustic Attenuation
Air Impingement Noise
Customer
Excitation Source, Energy Input
Structure-borne NVH
Structure Sensitivity
66
Design Principles Airborne NVHRadiated/Shell
Noise
  • Mechanism
  • Structural surface vibration imparts mechanical
    energy into adjacent acoustic fluid in the form
    of pressure waves at same frequency content as
    the surface vibration. These waves propagate
    through the fluid medium to the listener.
    Examples powertrain radiated noise, exhaust
    pipe/muffler radiated noise
  • Design principle(s)
  • Minimize the vibration level on the surface of
    the structure

67
Design Principles Airborne NVH Radiated/Shell
Noise
  • Design Action(s)
  • Stiffen Add ribbing, increase gauge thickness,
    change material to one with higher elastic
    modulus, add internal structural support
  • Minimize surface area Round surfaces
  • Damping Apply mastic adhesives to surface, make
    surfaces out of heavy rubber
  • Mass loading Add non-structural mass to reduce
    vibration amplitude --- (Only as a last resort)

68
Design Principles Airborne NVHTube
Inlet/Outlet Airflow Noise
  • Mechanism
  • Pressure waves are produced in a tube filled with
    moving fluid by oscillating (open/closed)
    orifices. These waves propagate down tube and
    emanate from the inlet or outlet to the listener.
    Examples induction inlet noise, exhaust
    tailpipe noise
  • Design principle(s)
  • Reduce the resistance in the fluid flow

69
Design Principles Airborne NVHTube
Inlet/Outlet Airflow Noise
  • Design action(s)
  • Make tubes as straight as possible
  • Include an in-line silencer element with
    sufficient volume
  • Locate inlet/outlet as far away from customer as
    possible
  • Design for symmetrical (equal length) branches

70
Design Principles Airborne NVHTube
Inlet/Outlet Airflow Noise
V6 Intake Manifolds
71
Design Principles Airborne NVHImpactive Noise
  • Mechanism
  • Two mechanical surfaces coming into contact with
    each other causes vibration in each surface,
    which imparts mechanical energy into adjacent
    acoustic fluid in the form of pressure waves at
    the same frequency as the surface vibration.
    These waves propagate through the fluid medium to
    the listener.
  • - Examples Tire impact noise, door closing
    sound, power door lock sound
  • Pressures waves caused by air pumping in and out
    of voids between contacting surfaces
  • - Examples Tire impact noise

72
Design Principles Airborne NVHImpactive Noise
Air Pumping Air forced in and out of voids is
called air pumping
73
Design Principles Airborne NVHImpactive Noise
  • Design principle(s)
  • Reduce the stiffness of the impacting surfaces
  • Increase damping of impacting surfaces
  • Design action(s)
  • Change material to one with more compliance,
    higher damping
  • Management of modal frequencies, mode shapes of
    impacting surfaces (tire tread pattern, tire
    cavity resonance)

74
Design Principles Airborne NVHAir Impingement
Noise
  • Mechanism
  • When an object moves through a fluid, turbulence
    is created which causes the fluid particles to
    impact each other. These impacts produce
    pressure waves in the fluid which propagate to
    the listener. Examples engine cooling fan,
    heater blower, hair dryer
  • Design principle(s)
  • Reduce the turbulence in the fluid flow

75
Design Principles Airborne NVHAir Impingement
Noise
  • Design action(s)
  • Design fan blades asymmetrically, with
    circumferential ring
  • Optimize fan diameter, flow to achieve lowest
    broad band noise
  • Use fan shroud to guide the incoming and outgoing
    airflow

76
NVH Design Principles
Source
Responder
Path
Radiated/Shell Noise
Acoustic Attenuation
Acoustic Attenuation
Tube Inlet/Outlet Noise
Environment Sensitivity
Airborne NVH
Impactive Noise
Acoustic Attenuation
Acoustic Attenuation
Air Impingement Noise
Customer
Excitation Source, Energy Input
Structure-borne NVH
Structure Sensitivity
77
Design Principles Airborne NVHAirborne Noise
Path Treatment
78
Design Principles Airborne NVHAirborne Noise
Path Treatment
  • Design principle(s)
  • Absorb noise from the source
  • Block the source noise from coming in
  • Absorb the noise after it is in
  • Design action(s)
  • Surround source with absorbing materials
  • Minimize number and size of pass-through holes
  • Use High-quality seals for pass-through holes
  • Add layers of absorption and barrier materials in
    noise path
  • Adopt target setting/cascading strategy

79
Design Principles Airborne NVHAirborne Noise
Path Treatment
  • Barrier performance is controlled mainly by mass
  • 3 dB improvement requires 41 higher weight
  • Mastic or laminated steel improves low frequency
  • Soft decoupled layers (10-30 mm) absorb sound
  • Pass-thru penetration seals weaker than steel

air absorption materials
80
NVH Design Principles
Source
Responder
Path
Radiated/Shell Noise
Acoustic Attenuation
Acoustic Attenuation
Tube Inlet/Outlet Noise
Environment Sensitivity
Airborne NVH
Impactive Noise
Acoustic Attenuation
Acoustic Attenuation
Air Impingement Noise
Customer
Excitation Source, Energy Input
Structure-borne NVH
Structure Sensitivity
81
Design Principles Airborne NVHAirborne Noise
Responder Treatment
  • Design principle(s)
  • Absorb noise at listener
  • Block noise at listener
  • Breakup of acoustic wave pattern
  • Design action(s)
  • Surround listener with absorbing materials
  • Ear plugs
  • Design the surrounding geometry to avoid standing
    waves
  • Add active noise cancellation/control devices

82
NVH Design Principles
Source
Path
Responder
Radiated/Shell Noise
Acoustic Attenuation
Acoustic Attenuation
Tube Inlet/Outlet Noise
Environment Sensitivity
Airborne NVH
Impactive Noise
Acoustic Attenuation
Acoustic Attenuation
Air Impingement Noise
Customer
Excitation Source, Energy Input
Structure-borne NVH
Structure Sensitivity
83
Design Principles Structureborne NVH
  • Structureborne NVH is created due to interaction
    between source, path,and responder.
  • Frequency separation strategy for excitation
    forces, path resonance and structural modes needs
    to be planned achieved to avoid NVH issues.

84
Design Principles Structureborne NVH
  • What happens if frequencies align?
  • If a structural element having a natural
    frequency of f is excited by a coupled source at
    many frequencies, including f, it will resonate,
    and could cause a concern depending on the path.
  • (This is exactly like a tuning fork.)

85
Design Principles Structureborne NVH
The steering column vibration will have an extra
large peak if the steering column mode coincides
with the overall bending mode.
86
Design Principles Structureborne NVH
Natural frequencies of major structures need to
be separated to avoid magnification.
87
Design Principles Structureborne NVH
  • In addition to adopting the modal
  • separation strategy, other principles are
  • listed below
  • Reduce excitation sources
  • Increase isolation as much as possible
  • Reduce sensitivity of structural response.

88
NVH Design Principles
Source
Responder
Path
Radiated/Shell Noise
Acoustic Attenuation
Acoustic Attenuation
Tube Inlet/Outlet Noise
Environment Sensitivity
Airborne NVH
Impactive Noise
Acoustic Attenuation
Acoustic Attenuation
Air Impingement Noise
Customer
Excitation Source, Energy Input
Structure-borne NVH
Structure Sensitivity
89
Design Principles Structureborne NVHExcitation
Source
  • Mechanism
  • Excitation source can be shown in the form of
    forces or vibrations. They are created by the
    movement of mass due to mechanical, chemical, or
    other forms of interactions.
  • Design principle(s)
  • Reduce the level of interactions as much as
    possible.
  • Take additional actions when it is impossible to
    reduce interactions.

90
Design Principles Structureborne NVHExcitation
Source
  • Design action(s)
  • Achieve high overall structural rigidity
  • Minimize unbalance
  • Achieve high stiffness at attachment points of
    the excitation objects

91
Design Principles Structureborne NVHExcitation
Source
A/C Compressor Bad Example

Cantilever Effect ? Less Rigid
92
Design Principles Structureborne NVHExcitation
Source
A/C Compressor - Good Example

93
NVH Design Principles
Source
Responder
Path
Radiated/Shell Noise
Acoustic Attenuation
Acoustic Attenuation
Tube Inlet/Outlet Noise
Environment Sensitivity
Airborne NVH
Impactive Noise
Acoustic Attenuation
Acoustic Attenuation
Air Impingement Noise
Customer
Excitation Source, Energy Input
Structure-borne NVH
Structure Sensitivity
94
Design Principles Structureborne NVHPath -
Isolation Strategy
  • Mechanism
  • Path transfers mechanical energy in the form of
    forces or vibration. Normally path is
    mathematically simulated by spring or damper.
  • Design principle(s)
  • Force or Vibration is normally controlled through
    maximizing transmission loss.
  • In the frequency range of system resonance,
    controlling damping is more effective for
    maximizing transmission loss.
  • In the frequency range outside of the system
    resonance, controlling stiffness or mass is more
    effective for maximizing transmission loss.

95
Design Principles Structureborne NVHPath -
Isolation Strategy
  • Design action(s)
  • Maximize damping in the frequency range of system
    resonance by using higher damped materials, (e.g.
    hydraulic engine mounts). Tuned damper can also
    be used.
  • Adjust spring rate (e.g. flexible coupler or
    rubber mount) to avoid getting into resonant
    region and maximize transmission loss
  • If nothing else works or is available, use dead
    mass as tuning mechanism.

96
Design Principles Structureborne NVHPath -
Isolation Strategy
Tuning and Degree of Isolation

By moving natural frequency down for this system
it increased damping at 100 Hz
97
NVH Design Principles
Source
Responder
Path
Radiated/Shell Noise
Acoustic Attenuation
Acoustic Attenuation
Tube Inlet/Outlet Noise
Environment Sensitivity
Airborne NVH
Impactive Noise
Acoustic Attenuation
Acoustic Attenuation
Air Impingement Noise
Customer
Excitation Source, Energy Input
Structure-borne NVH
Structure Sensitivity
98
Design Principles Structureborne NVHStructure
Sensitivity Strategy
  • Mechanism
  • Structural motion that results when input force
    causes the structure to respond at its natural
    modes of vibration.
  • Design principle(s)
  • Reduce the amplitude of structural motions by
  • controlling stiffness and mass (quantity and
    distribution),
  • managing excitation input locations

99
Design Principles Structureborne NVHStructure
Sensitivity Strategy
  • Design action(s)
  • Select architecture that can provide the maximal
    structural stiffness by properly placing and
    connecting structure members.
  • Use damping materials to absorb mechanical energy
    at selected frequencies.
  • Distribute structural mass to alter vibration
    frequency or mode shape.
  • Locate excitation source at nodal points of
    structural modes.

100
Design Principles Structureborne NVHStructure
Sensitivity Strategy
Body Modes and Body Architecture
  • How Does Architecture Influence Body NVH?
  • Governs the way external loads are reacted to and
    distributed throughout the vehicle
  • Affects Stiffness, Mass Distribution Modes
  • What Controls Body Architecture?
  • Mechanical Package
  • Interior Package
  • Styling
  • Customer Requirements
  • Manufacturing
  • Fixturing
  • Assembly Sequence
  • Stamping
  • Welding
  • Material Selection

101
Design Principles Structureborne NVHStructure
Sensitivity Strategy
Body Modes and Body Architecture
102
Design Principles Structureborne NVHStructure
Sensitivity Strategy
Body Modes and Body Architecture
103
Design Principles Structureborne NVHStructure
Sensitivity Strategy
Body Modes and Mass Distribution
  • Effect of Mass Placement on Body Modes
  • Adding mass to the body lowers the mode frequency
  • Location of the mass determines how much the mode
    frequency changes.

104
Design Principles Structureborne NVHStructure
Sensitivity Strategy
  • Metrics used to quantify body structure vibration
    modes
  • Global dynamic and static response for vertical /
    lateral bending and torsion
  • Local dynamic response (point mobility V/F) at
    body interfaces with major subsystems

105
Design Principles Structureborne NVHStructure
Sensitivity Strategy
Guideline Body Modes Force Input Locations
  • Where Possible Locate Suspension Powertrain
    Attachment Points to Minimize Excitation
  • Forces applied to the body should be located near
    nodal points.
  • Moments applied to the body should be located
    near anti-nodes.

106
Design Principles Structureborne NVHStructure
Sensitivity Strategy
  • Conclusions
  • The body structure is highly interactive with
    other subsystems from both design and functional
    perspective. Trade-offs between NVH and other
    functions should be conducted as soon as
    possible.
  • Once the basic architecture has been developed,
    the design alternatives to improve functions
    become limited.

107
Design For NVH (DFNVH)
  • Introduction to NVH
  • DFNVH Heuristics
  • DFNVH Process Flow and Target Cascade
  • DFNVH Design Process Fundamentals
  • Key DFNVH Principles
  • Airborne NVH
  • Radiated/Shell Noise
  • Tube Inlet/Outlet Noise
  • Impactive Noise
  • Air Impingement Noise
  • Structure-Borne NVH
  • Wind Noise Example
  • 2002 Mercury Mountaineer Case Study
  • Summary

108
Wind Noise Example
  • Any noise discernible by the human ear which is
    caused by air movement around the vehicle.
  • Sources aerodynamic turbulence, cavity
    resonance, and aspiration leaks.
  • Paths unsealed holes or openings and
    transmission through components.

109
Wind Noise Example
Wind Noise Target Cascade Diagram
110
Wind Noise Example
111
Wind Noise Example
Aerodynamic excitation
  • Exterior ornamentation turbulence
  • Cavity resonances
  • Air flow induced panel resonances
  • Air extractor noise ingress
  • Door seal gaps, margins and offsets
  • A-pillar vortex
  • Mirror wake
  • Antenna vortex
  • Wiper turbulence
  • Windshield turbulence
  • Leaf screen turbulence

112
Wind Noise Example
Aspiration leakage
  • Dynamic sealing
  • Closures
  • Dynamic weatherstrip
  • Glass runs
  • Beltline seals
  • Drain holes
  • Moon roof
  • Glass runs
  • Backlite slider
  • Glass runs
  • Latch
  • Static sealing
  • Fixed backlite
  • Exterior mirror seal
  • Air extractor seal
  • Moon roof
  • Door handle lock
  • Exterior door handles
  • Windshield
  • Trim panel watershield
  • Floor panel
  • Rocker

113
  • Introduction to NVH
  • DFNVH Design Process Fundamentals
  • Key DFNVH Principles
  • Airborne NVH
  • Radiated/Shell Noise
  • Tube Inlet/Outlet Noise
  • Impactive Noise
  • Air Impingement Noise
  • Structure-Borne NVH
  • Wind Noise Example
  • 2002 Mercury Mountaineer Case Study
  • Summary

114
Design For NVH 2002 Mercury Mountaineer SUV
Case Study
  • Creating a quieter and more pleasant cabin
    environment, as well as reducing overall noise,
    vibration, and harshness levels, were major
    drivers when developing the 2002 Mercury
    Mountaineer.
  • The vehicle had more than 1,000 NVH targets,
    that fell into three main categories road noise,
    wind noise, and powertrain noise. No area of the
    vehicle was immune from scrutiny Ray Nicosia,
    Veh. Eng. Mgr.


115
Design For NVH 2002 Mercury Mountaineer SUV
The body shell is 31 stiffer than previous
model, and exhibits a 61 improvement in lateral
bending. Laminated steel dash panel, and
magnesium cross beam were added.
116
Design For NVH 2002 Mercury Mountaineer SUV
  • Improved chassis rigidity via a fully boxed frame
    with a 350 increase in torsional stiffness and a
    26 increase in vertical and lateral bending.

117
Design For NVH 2002 Mercury Mountaineer
  • Aachen Head was used to improve Mountaineers
    Speech Intelligibility Rating to a 85. A rating
    of 85 means passengers would hear and understand
    85 of interior conversation. Industry average
    for Luxury SUV is upper 70s.

118
Design For NVH 2002 Mercury Mountaineer
Body sculpted for less wind resistance with glass
and door edges shifted out of airflow.
119
DFNVH Summary
  • Preventing NVH issues up front through proper
    design is the best approach downstream
    find-and-fix is usually very expensive and
    ineffective
  • Follow systems engineering approach use cascade
    diagram to guide development target setting.
    Cascade objective vehicle level targets to
    objective system and component targets

120
DFNVH Summary
  • Use NVH health chart to track design status
  • Always address sources first
  • Avoid alignment of major modes
  • Use the Source-Path-Responder approach

121
References
  • Ford-Intranet web site
  • http//www.nvh.ford.com/vehicle/services/training
  • General NVH
  • NVH Awareness
  • NVH Jumpstart
  • NVH Literacy
  • Wind Noise
  • Handbook of Noise Measurement by Arnold P.G.
    Peterson, Ninth Edition, 1980
  • Sound and Structural Vibration by Frank Fahy,
    Academic Press, 1998
  • http//www.needs.org - Free NVH courseware

122
References
  • "Body Structures Noise and Vibration Design
    Guidance", Paul Geck and David Tao, Second
    International Conference in Vehicle Comfort, 
    October 14-16, 1992, Bologna, Italy.
  • "Pre-program Vehicle Powertrain NVH Process",
    David Tao, Vehicle Powertrain NVH Department,
    Ford Advanced Vehicle Technology, September,
    1995.
  • Fundamentals of Noise and Vibration Analysis for
    Engineers, M.P. Norton, Cambridge University
    Press, 1989
  • Modern Automotive Structural Analysis, M.
    Kamal,J. Wolf Jr., Van Nostrand Reinhold Co.,
    1982
  • http//www.nvhmaterial.com
  • http//www.truckworld.com
  • http//www.canadiandriver.com
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