Df Nvh June 2007

*Design For NVHMPD575 DFXJonathan Weaver

*Development HistoryOriginally developed by Cohort 1 students: Jeff Dumler, Dave McCreadie, David TaoRevised by Cohort 1 students: T. Bertcher, L. Brod, P. Lee, M. WehrRevised by Cohort 2 students: D. Gaines, E. Donabedian, R. Hall, E. Sheppard, J. Randazzo

*Design For NVH (DFNVH) Introduction to NVHDFNVH HeuristicsDFNVH Process Flow and Target CascadeDFNVH Design Process FundamentalsKey DFNVH PrinciplesAirborne NVHRadiated/Shell NoiseTube Inlet/Outlet NoiseImpactive NoiseAir Impingement NoiseStructure-Borne NVHWind Noise Example2002 Mercury Mountaineer Case StudySummary

* 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.

* Introduction to NVH What is NVH?

Noise: Typically denotes unwanted sound, hence treatments are normally to eliminate or reduce Variations are detected by earCharacterized by frequency, level & qualityMay be Undesirable (Airborne)May be Desirable (Powerful Sounding Engine)

*Introduction to NVH What is NVH?VibrationAn oscillating motion about a reference point which occurs at some frequency or set of frequenciesMotion sensed by the body (structureborne)mainly in 0.5 Hz - 50 Hz rangeCharacterized by frequency, level and directionCustomer Sensitivity Locations are steering column, seat track, toe board, and mirrors (visible vibrations)

*Introduction to NVH What is NVH?HarshnessLow-frequency (25 -100 Hz) vibration of the vehicle structure and/or componentsFrequency range overlaps with vibration but human perception is different.Perceived tactilely and/or audiblyRough, grating or discordant sensation

*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

*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

*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.

*Introduction to NVH What is NVH?Barriers: Design Parameters Location (close to source)Material (cost/weight)Mass per Unit AreaNumber and Thickness of LayersNumber and Size of Holes


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.


Absorbers: Design Parameters

Area of absorbing material (large as possible)

Type of material (cost/weight)

Thickness (package/installation)


Damping:Defined as a treatment of vibration to reduce the magnitude of targeted vibrationsDamping 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


Damping: Design ParametersDensity (low as possible)Stiffness (high as possible)Thickness (damping increases with the square of thickness)Free surface versus constrained layerConstrained 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


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.


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 ratesCompliant (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.

*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

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

*Introduction to NVHWhy Design for NVH?SUSTAIN / BUILD65%85%59RelativeLeverageIMPROVEREVIEWMAINTAINOverall HandlingCup holdersExterior Styling**6.977%Corporate Leverage vs. Customer SatisfactionNVH Customer Satisfaction Needs Improvement at 3 MIS*

*Introduction to NVHWhy Design for NVH?NVH Can Both Dissatisfy and Delight+ Performance+ CustomerSatisfaction- PerformanceDissatisfiersHarley Mustang LexusLoudnessUnusual NoisesTGWSound QualityTGRKANO Model+ Degree of AchievementBasic Quality(Inhibitors)Performance Quality(Attributes)- CustomerSatisfactionExciting Quality(Surprise & Delight)Axle Whine Wind Noise

*Introduction to NVHWhy Design for NVH?Customers place a high value on NVH performance in vehiclesAbout 1/3 of all Product / Quality Complaints are NVH-related

Summary of Customer Importance

*Introduction to NVHWhy Design for NVH?About 1/5 of all Warranty costs are NVH-relatedDealer may spend many hours to determine source of NVH problemDealer 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 delightSummary of Customer Importance (continued)

*Design For NVH HeuristicsDesign the structure with good "bones"If the NVH problem is inherent to the architecture, it will be very difficult to tuneit 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)

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Cost rulesOnce the architecture is selected, it will be very costly to re-select another architecture. Therefore, any bad design will stay fora long time 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 seefunctions from the system, but sound designs requires our ability to develop requirements of the parts by cascadingfunctional requirements from the system

Design For NVH Heuristics

*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)

DFNVH Process Flow and Target Cascade

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DFNVH Process Flow and Target Cascade Noise Reduction Strategy: Targets are even set for the noise reduction capability of the sound package.

* DFNVH Process Flow and Target Cascade Systems Engineering V and PD Process Timing

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* DFNVH Process Flow and Target Cascade NVH Functional AttributeSub -AttributesRoadP/TWindBrakeComp. S.Q.S&RPass-by Noise (Reg.)

*DFNVH Process Flow and Target Cascade Convert attribute target strategy to objective targets

* DFNVH Process Flow and Target Cascade Acceleration NVH Target Cascade

* 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.

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Operating ConditionNVH Concerns IdleShake and boom due to engine torque.LuggingShake and boom due to engine torque.WOTNoise and vibration due to engine, exhaust vibration, and radiated noise.Cruise (smooth road)Shake, roughness, and boom due to tire and powertrain imbalance and tire force variation, Wind noise, Tire NoiseCruise (rough road)Road noise and shake Tip-in"Moan" due to powertrain bending. BrakingSqueal due to brake stick-slip.

*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.

*DFNVH Process Flow and Target Cascade

NVH AspectSubjective ResponseBoom Low frequency sound 20 - 100 hz. DroneLarge amplitude pure tone in the region 100-200 hz GrowlModulated low/medium frequency broad band noise 100-1000 hz GroanTransient broadband noise with noticeable time variation and tone content, 50-250 hz MoanA sound in the 80 to 200 Hz range, frequently consisting of one or two tonesSqueakHigh pitched broadband transient noise. WhineMid-frequency to high frequency pure tone (possibly with harmonics), 200-2000 hz

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DFNVH Process Flow and Target Cascade SummaryNoise 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.

*Design For NVH (DFNVH) Introduction to NVHDFNVH HeuristicsProcess Flow and Target CascadeDFNVH Design Process FundamentalsKey DFNVH PrinciplesAirborne NVHRadiated/Shell NoiseTube Inlet/Outlet NoiseImpactive NoiseAir Impingement NoiseStructure-Borne NVHWind Noise Example2002 Mercury Mountaineer Case StudySummary

*DFNVH Process FundamentalsSource-Path-ResponderEngine Firing PulsesDriveshaft ImbalanceRough RoadTire ImbalanceSpeed BumpGear MeshingBody-Shape Induced VorticesExcitation Source Examples:

*DFNVH Process FundamentalsSource-Path-ResponderTendency of the path to transmit energy from the source to the responder, commonly referred to as the transfer function of the systemSensitivity:

*DFNVH Process Fundamentals Source-Path-ResponderExample: Body Sensitivity

TactilePoint mobility (v/F) (Structural velocity induced by force)AcousticAirborne (p/p)(Airborne sound pressure induced by pressure waves)Structureborne (p/F)(Airborne sound pressure induced by force)

*DFNVH Process Fundamentals Source-Path-Responder

Body Sensitivity Demonstration

Point Mobility

Typical Point Mobility Spectrum for Compliant & Stiff StructuresPoint Mobility (V/F)MoreCompliantLessCompliantFrequency ( f )50140

*DFNVH Process FundamentalsSource-Path-ResponderS/W = Steering Wheel

*DFNVH Process FundamentalsSource-Path-ResponderPowertrain Noise Model

*DFNVH Process FundamentalsSource-Path-ResponderRoad Noise Model

*DFNVH Process FundamentalsSource-Path-ResponderDriveline Model

*DFNVH Process FundamentalsSound QualityWhat is Sound Quality?Historically, Noise Control meant reducing sound levelFocus was on major contributors (P/T, Road, Wind Noise)Sound has multiple attributes that affect customer perceptionAll vehicle sounds can influence customer satisfaction(e.g., component Sound Quality)Noise Control no longer means simply reducing dB levels

*DFNVH Process FundamentalsSound QualityWhy Sound Quality?Generally not tied to any warranty issueImportant to Customer Satisfaction- Purchase experience (door closing)- Ownership experience (powertrain/exhaust)

A strong indicator of vehicle craftsmanship- Brand image (powertrain)

*DFNVH Process FundamentalsSound QualityThe Sound Quality Process1. Measurement (recording)2. Subjective evaluation (listening studies) Actual or surrogate customers3. Objective analysis Sound quality Metrics4. Subjective/Objective correlation5. Component design for sound quality

*DFNVH Process FundamentalsSound QualityBinaural Acoustic Heads Stereo Sound Recording representing sound wave interaction w/ human torso

*DFNVH Process FundamentalsSound QualitySound Quality Listening RoomUsed for Customer Listening Clinics.

*DFNVH Process FundamentalsSound QualityPoor Sound QualityGood Sound Quality

*DFNVH Process FundamentalsSound QualityQuantifying Door Closing Sound Quality1. Sound Level (Loudness)

2. Frequency Content (Sharpness)

3. Temporal Behavior

*DFNVH Process FundamentalsSound QualityWhat Makes A Good Door Closing Sound? Good Sound Poor SoundQuiet Loud

Low Frequency High Frequency (Solid) (Tinny, Cheap)

One Impact Rings On (Bell)

No Extraneous NoiseRattles, Chirps, etc.

*DFNVH Process FundamentalsSound QualityExample: Qualifying Door Closing Sound QualityGoodBadLevel (dBa)(color)Frequency (Hz)(y-axis)Time (sec.) (x-axis)

*DFNVH Process FundamentalsSound QualityDesign for Sound QualityDoor Closing ExamplePerceived SoundStructure-borneAirborneSeal Trans LossLatch ForcesStr. ComplianceInertiaSpring RatesMaterialRadiated Snd.

*ConclusionsSound Quality is critical to Customer SatisfactionUnderstand sound characteristics that govern perceptionUpfront implementation is the biggest challenge Use commodity approach to component sound qualityGeneric targets, supplier awareness, bench testsDFNVH Process FundamentalsSound Quality

*Design For NVH (DFNVH) Introduction to NVHDFNVH HeuristicsProcess Flow and Target CascadeDFNVH Design Process FundamentalsKey DFNVH PrinciplesAirborne NVHRadiated/Shell NoiseTube Inlet/Outlet NoiseImpactive NoiseAir Impingement NoiseStructure-Borne NVHWind Noise Example2002 Mercury Mountaineer Case StudySummary

*NVH Design PrinciplesDynamic System NVH Model:Source X Path = ResponseAlways work on sources firstReduce the level of ALL sources by using quiet commoditiesPath 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 levelOnly resort to tuning in the late stage of design

*NVH Design Principles Tube Inlet/Outlet NoiseExcitationSource, Energy InputStructureSensitivity

Customer

Airborne NVHStructure-borneNVHAir Impingement NoiseSourcePathResponderImpactive NoiseRadiated/Shell NoiseAcoustic AttenuationAcoustic AttenuationAcoustic AttenuationAcoustic AttenuationEnvironmentSensitivity

*NVH Design PrinciplesTube Inlet/Outlet NoiseExcitationSource, Energy InputStructureSensitivity

Customer


*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

Design Principles Airborne NVHRadiated/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)Design Principles Airborne NVH Radiated/Shell 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

Design Principles Airborne NVHTube Inlet/Outlet Airflow Noise

*Design action(s):Make tubes as straight as possibleInclude an in-line silencer element with sufficient volumeLocate inlet/outlet as far away from customer as possibleDesign for symmetrical (equal length) branches

Design Principles Airborne NVHTube Inlet/Outlet Airflow Noise

*Design Principles Airborne NVHTube Inlet/Outlet Airflow NoiseV6 Intake Manifolds

*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 noiseDesign Principles Airborne NVHImpactive Noise

*Design Principles Airborne NVHImpactive NoiseAir PumpingAir forced in and out of voids is called air pumping

*Design principle(s):Reduce the stiffness of the impacting surfacesIncrease damping of impacting surfaces

Design action(s):Change material to one with more compliance, higher dampingManagement of modal frequencies, mode shapes of impacting surfaces (tire tread pattern, tire cavity resonance)Design Principles Airborne NVHImpactive 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

Design Principles Airborne NVHAir Impingement Noise

*Design action(s):Design fan blades asymmetrically, with circumferential ringOptimize fan diameter, flow to achieve lowest broad band noiseUse fan shroud to guide the incoming and outgoing airflowDesign Principles Airborne NVHAir Impingement Noise


Customer


*Design Principles Airborne NVHAirborne Noise Path Treatment

*Design principle(s):Absorb noise from the sourceBlock the source noise from coming inAbsorb the noise after it is in

Design action(s):Surround source with absorbing materialsMinimize number and size of pass-through holesUse High-quality seals for pass-through holes Add layers of absorption and barrier materials in noise pathAdopt target setting/cascading strategyDesign Principles Airborne NVHAirborne Noise Path Treatment

*air absorption materialsDesign Principles Airborne NVHAirborne Noise Path TreatmentBarrier performance is controlled mainly by mass3 dB improvement requires 41% higher weightMastic or laminated steel improves low frequencySoft decoupled layers (10-30 mm) absorb soundPass-thru penetration seals weaker than steel


Customer


*Design principle(s):Absorb noise at listenerBlock noise at listenerBreakup of acoustic wave pattern

Design action(s):Surround listener with absorbing materialsEar plugsDesign the surrounding geometry to avoid standing wavesAdd active noise cancellation/control devicesDesign Principles Airborne NVHAirborne Noise Responder Treatment


Customer


*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. 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.)Design Principles Structureborne NVH

*Design Principles Structureborne NVHThe steering column vibration will have an extra large peak if the steering column mode coincides with the overall bending mode.

*Design Principles Structureborne NVHNatural frequencies of major structures need to be separated to avoid magnification.

*In addition to adopting the modal separation strategy, other principles are listed below:

Reduce excitation sourcesIncrease isolation as much as possibleReduce sensitivity of structural response.

Design Principles Structureborne NVH


Customer


*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. 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 Design Principles Structureborne NVHExcitation Source

* Design Principles Structureborne NVHExcitation SourceA/C Compressor Bad ExampleCantilever Effect Less Rigid

* Design Principles Structureborne NVHExcitation SourceA/C Compressor - Good Example

*NVH Design Principles Tube Inlet/Outlet NoiseExcitationSource, Energy InputStructureSensitivity

Customer


*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. 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 lossIf nothing else works or is available, use dead mass as tuning mechanism. Design Principles Structureborne NVHPath - Isolation Strategy

* Design Principles Structureborne NVHPath - Isolation StrategyTuning and Degree of IsolationBy moving natural frequency down for this system it increased damping at 100 Hz


Customer


*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 locationsDesign 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. Design Principles Structureborne NVHStructure Sensitivity Strategy

*How Does Architecture Influence Body NVH?Governs the way external loads are reacted to and distributed throughout the vehicleAffects Stiffness, Mass Distribution & Modes

What Controls Body Architecture?Mechanical PackageInterior PackageStylingCustomer RequirementsManufacturingFixturingAssembly SequenceStampingWeldingMaterial SelectionDesign Principles Structureborne NVHStructure Sensitivity StrategyBody Modes and Body Architecture

*Design Principles Structureborne NVHStructure Sensitivity StrategyBody Modes and Body Architecture

*Design Principles Structureborne NVHStructure Sensitivity StrategyBody Modes and Mass DistributionEffect of Mass Placement on Body ModesAdding mass to the body lowers the mode frequencyLocation of the mass determines how much the mode frequency changes.

*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 subsystemsDesign Principles Structureborne NVHStructure Sensitivity Strategy

*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.Design Principles Structureborne NVHStructure Sensitivity StrategyGuideline: Body Modes & Force Input Locations

*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. Design Principles Structureborne NVHStructure Sensitivity Strategy

*Wind Noise ExampleAny 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.

*Wind Noise Target Cascade DiagramWind Noise Example

*Wind Noise Example

*Aerodynamic excitationA-pillar vortexMirror wakeAntenna vortexWiper turbulenceWindshield turbulenceLeaf screen turbulenceExterior ornamentation turbulenceCavity resonancesAir flow induced panel resonancesAir extractor noise ingressDoor seal gaps, margins and offsetsWind Noise Example

*Aspiration leakageDynamic sealingClosuresDynamic weatherstripGlass runsBeltline sealsDrain holesMoon roofGlass runsBacklite sliderGlass runsLatchStatic sealingFixed backliteExterior mirror sealAir extractor sealMoon roofDoor handle & lockExterior door handlesWindshieldTrim panel & watershieldFloor panelRockerWind Noise Example

*Introduction to NVHDFNVH Design Process FundamentalsKey DFNVH PrinciplesAirborne NVHRadiated/Shell NoiseTube Inlet/Outlet NoiseImpactive NoiseAir Impingement NoiseStructure-Borne NVHWind Noise Example2002 Mercury Mountaineer Case StudySummary

* 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.

* 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.

* Design For NVH 2002 Mercury Mountaineer SUVImproved chassis rigidity via a fully boxed frame with a 350% increase in torsional stiffness and a 26% increase in vertical and lateral bending.

* 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.

* Design For NVH 2002 Mercury Mountaineer Body sculpted for less wind resistance with glass and door edges shifted out of airflow.

*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

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

DFNVH Summary

*ReferencesFord-Intranet web site:http://www.nvh.ford.com/vehicle/services/trainingGeneral NVHNVH AwarenessNVH JumpstartNVH LiteracyWind NoiseHandbook of Noise Measurement by Arnold P.G. Peterson, Ninth Edition, 1980Sound and Structural Vibration by Frank Fahy, Academic Press, 1998http://www.needs.org - Free NVH courseware

*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, 1989Modern Automotive Structural Analysis, M. Kamal,J. Wolf Jr., Van Nostrand Reinhold Co., 1982http://www.nvhmaterial.comhttp://www.truckworld.comhttp://www.canadiandriver.com

****20Hz to 20KHz audible

1. BEFORE: The science of managing these factors in automobile designAFTER: The science of managing vibration frequencies in automobile design

BEFORE: but in an era when fuel economy demands are forcing the designers to lighten the carAFTER: but in an era when fuel economy demands are forcing designers to lighten the car

***Class Question: is there a clear distinction between vibration and harshness?Look at metrics later to see distinction.

3. BEFORE: Perceived tactically AFTER: Perceived tactilely *4. BEFORE: Kind of sound that most people think of as noise and travels through gaseous mediums like the air. AFTER: Kind of sound most people think of as noise, and travels through gaseous mediums like air.

5. BEFORE: Some people classify human voice as airborne noise but a better example is the hum of your computer or air conditionerAFTER: Some people classify human voice as airborne noise, but a better example is the hum of your computer, or air conditioner.

6. BEFORE: Detected by human ear and most likely impossible to detect with your sense of touchAFTER: Detected by the human ear, and most likely impossible to detect with the sense of touch.

*7. BEFORE: Vibration that you predominately feel like a deep booming base sound AFTER: Vibration that you predominately feel, like a deep booming bass sound

8. BEFORE: Vibration that you predominately feel like a deep booming base sound from the cars radio next to you at a stoplightAFTER: Vibration that you predominately feel, like the deep booming bass sound from the car radio next to you at a stoplight*9. BEFORE: Barrier performance is dependent on frequency and is best used to treat high frequencies.AFTER: Barrier performance is dependent on frequency, and is best used to treat high frequencies.

10. BEFORE: If no gaps exist when the barrier is employed then weight becomes the dominant factor in comparing barriers.AFTER: If no gaps exist when the barrier is employed, then weight becomes the dominant factor in comparing barriers.

**Carpet is another absorber, though its principle NVH function is as a barrier.

11. BEFORE: Reduces sound by absorbing the energy of the sound waves and dissipating through heatAFTER: Reduces sound by absorbing the energy of the sound waves, and dissipating it as heat

12. BEFORE: it as heat. Headliner, hood insulator. AFTER: it as heat. Examples: headliner, and hood insulator.

13. BEFORE: that trap sound waves and prevent reflecting back into the air.AFTER: that trap sound waves, and prevent reflection back into the air.

***14. BEFORE: Constrained layer damping more efficient than free surface damping on a weight and package basis, but is expensive and raises assembly issuesAFTER: Constrained layer damping is more efficient than free surface damping on a weight and package basis, but is expensive, and raises assembly issues*15. BEFORE: All isolation materials perform differently at different frequencies, and if engineered incorrectly may make NVH problem worse, instead of improving. AFTER: All isolation materials perform differently at different frequencies, and if engineered incorrectly, may make NVH problems worse instead of better.

**Explain the meaning of each of the 4 quadrants as described below during the discussion if people do not understand. REVIEW leverage is low and satisfaction is low, you need to review prior to changing / improving upon items in this area.MAINTAIN leverage is low and satisfaction is high; no need to improve, but do not degradeSUSTAIN leverage is high and sat. is high; no need to improve, but do not degradeIMPROVE Leverage is high and sat. is low; items in this quadrant need to be improved upon.NVH falls into this quadrant on many vehicles because although NVH is an attribute it is not the main function of any sub-system and often is not considered early in the design or resources are not committed. Overall in the industry the trend is that NVH is becoming more important and needs to be focused on earlier. This is especially true as customers begin to demand more, the competition gets better and the quality of the sub-systems and components improve, the noise floor begins to drop and more NVH issues surface.

**Explain TGWs: put in more generic terms for more general audience.Clarify: NVH because it is impending failure/failure or NVH w/out functional issue tied to it. Can also go the other way: R&R even when no functional problem.Data from quarterback analysis of AWS data.Two biggest warranty are squeak and rattle and windnoise within the NVH catagories.

***good*16. BEFORE: For example, on the basis of economics and timing, power plants (engines) are chosen which are known to be noisy. AFTER: For example, on the basis of economics and timing, power plants (engines) which are known to be noisy are chosen. *********Things to discuss while presenting this slide:Why poor: rougher, more modulatedWhy good: streamlined frequency content and order contentDifference wouldnt show up in overall sound level plot (about the same)Good sound quality is subjective: ie, want some roughness in a Mustang vs. no sound for a Lincoln.Slides in presentation but not here: WOT for 3 car examples v6 and 3 samples V8.Suggest: explain the difference between the 6 sounds. What are we listening to?Customer sound memory is very short.*Good.*Add titles for axes: frequency, level, time*Good: conclusions for each section.*17. BEFORE: Reduce the level of ALL sources by using the quiet commoditiesAFTER: Reduce the level of ALL sources by using quiet commodities****Dont talk too much to this slide, use the next slides for in-depth discussion.*18. BEFORE: 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 same frequency content as the surface vibration. AFTER: 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.*Talk about tradeoffs: quite tires vs. traction and off road tough looks.

***Good organization of design rules with this central slide. *Separated into bullets for easier reading and understanding*19. BEFORE: If a structural element has a natural frequency of f and it is excited by coupled source at the many frequencies including f it will resonate and could cause a concern depending on the path. AFTER: 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. ***Discuss the Reasons: 200 hz is higher than 1st order engine or 1st order halfshaft and will not be excited.500 hz is higher than engine firing for V-8 engines that can rotate up to 6500 rpm {8*6500/(2*60)=433hz}***Shows slight change in spring rate equals difference in degree of damping*When talking to this slide discuss how for the first bullet point at least that CAE can be used to help early in the process.*Note this slide is different than as presented: Split into five. Good discussion about the tradeoffs between package space and stiffness.*Put mass at nodal point to avoid dropping frequency.*Good discuss how this data can be used in the model for upfront work

*Good discussion of trade-offs! And upfront planning

*20. BEFORE: Sources: aerodynamic turbulence, cavity resonances, aspiration leaks.AFTER: Sources: aerodynamic turbulence, cavity resonance, and aspiration leaks.*Ford confidential?**Very good wrap-up.

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Df Nvh June 2007