design for nvh
DESCRIPTION
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 students: T. Bertcher, L. Brod, P. Lee, M. Wehr - PowerPoint PPT PresentationTRANSCRIPT
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Design For NVH
MPD575 DFX
Jonathan Weaver
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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 : D. Gaines, E. Donabedian, R. Hall, E. Sheppard, J. Randazzo, J. Torres, B. Dhruna, J. Stevens, D. Kammerzell
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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
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● Vibration is movement, and vibration that reaches the
passenger compartment at the right frequency is noise.
● The science of managing the vibration frequencies in automobile design is called NVH - Noise, Vibration, and Harshness.
● It is relatively easy to reduce noise and vibration by adding weight thereby changing the natural frequency, 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?
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Introduction to NVH What is
NVH?
Noise:
•Typically denotes unwanted sound, hence treatments are normally implemented to eliminate or reduce it
•Variations are detected by ear
•Characterized by frequency, level & quality
•May be Undesirable (Airborne)
•May be Desirable (Powerful Sounding Engine)
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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 (structure-borne)– mainly in 0.5 Hz - 50 Hz range
• Characterized by frequency, magnitude and direction• Customer Sensitivity Locations are steering column, seat
track, toe board, and mirrors (visible vibrations)
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Introduction to NVH What is NVH?
• Harshness– Low-frequency (25 -100 Hz) vibration of the
vehicle structure and/or components– Frequency range overlaps with the vibration
frequencies but human perception of it is different.• Perceived tactilely and/or audibly• Rough, grating or discordant sensation• Unpleasant
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Introduction to NVH What is NVH
Airborne Noise:● Sound most people interpret as noise, and travels
through gaseous mediums like air.● Some people classify human voice as airborne noise, a
better example is the hum of your computer, or an air conditioner.
● Detected by the human ear and most likely impossible to detect with the sense of touch.
● Treatment/Countermeasures: Elimination of the source if possible; Barriers or Absorbers if not.
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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
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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 installed. A partially open door is a less effective barrier than a totally closed door.
•Barrier performance is dependent on frequency, and isbest used to treat high frequencies.
•If no gaps exist when the barrier is employed, then weight becomes the dominant factor in comparing barriers.
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Introduction to NVH What is NVH?
Barriers: Design Parameters • Location (close to source)• Material (cost/weight)• Mass per Unit Area• Number, Direction and Thickness of Layers• Number and Size of Holes
Note: Active Noise Cancellation (ANC) is a recent method discussed in this DFX. For airborne noise it can work between 30 and 1000 Hz to change the noise heard. ANC units offset unwanted sound by emitting opposing frequencies that “cancel” the unwanted sound. ANC technology is available in cars like the Lincoln MKS, Honda Odyssey, and Infiniti Q50
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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•Absorbers are ranked by the ability to absorb sound that otherwise would be reflected off its surface•Good absorber design contains 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)
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Introduction to NVH What is NVH?
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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 and location specific added mass
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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
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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.
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Introduction to NVH What is NVH?
Isolation by Bushings and Mounts:•Excitations are generally applied to or by 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.
Introduction to NVH How is NVH Measured?
One of the challenges of measuring and analyzing powertrain NVH is the large range in the absolute levels of sounds and vibrations that occur. Measurement and analysis require observation of small (low-level) signals in the presence of large (high-level) signals. This is required due to the capability of the human ear to process signals at a wide range of levels.
Introduction to NVH How is NVH Measured?
Amplitude Scales: The ratio between the largest and smallest signals that we can analyze is the dynamic range. Using a linear amplitude measurement scale limits our ability to display a wide dynamic range simultaneously as shown on Graph A. However, as shown on Graph B of the same sound, a logarithmic amplitude scale compresses large amplitude signals and expands small ones so that we can display a wide dynamic range simultaneously for analysis. This is why we use the logarithmic
decibel (dB) scale to measure sounds and vibrations
Introduction to NVH How is NVH Measured?
Amplitude Scales: The decibel (dB) is a logarithmic representation of an amplitude ratio. It is 20 times the base 10 logarithm of the ratio of the measured amplitude to a reference. In the case of sound, the units of measure are pressure and the reference is typically the threshold of hearing. On the dB scale, 0 dB approximately corresponds to the normal threshold of human hearing and 140 dB approximately corresponds to the threshold of pain. Each 1 dB step approximately represents the smallest change in sound level that normal human hearing can detect 50% of the time. The table compares dB levels for various sounds at 1 meter and 10 meters. To become more familiar with dB levels.
Introduction to NVH How is NVH Measured?
Amplitude Scales: The formula for calculating sound pressure level (SPL) in decibel (dB) is:
Adding decibel (dB): Because the dB scale is a logarithmic ratio, we cannot add dB levels directly. To add two dB values, we must apply the rules of logarithms as follows:
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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
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Introduction to NVHWhy Design for NVH?
• NVH impacts Customer Satisfaction
• NVH impacts Warranty
• NVH has financial impact
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Introduction to NVHWhy Design for NVH?
65%
85%
5
9
RelativeLeverage
IMPROVE
REVIEW MAINTAIN
Overall Handling
Cup holders Exterior
Styling
* *
6.9
77%
Corporate Leverage vs. Customer SatisfactionNVH Customer Satisfaction Needs Improvement at 3 MIS
*NVH SUSTAIN / BUILD
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Introduction to NVHWhy Design for NVH?
NVH Can Both Dissatisfy and Delight
+ Performance
+ CustomerSatisfactio
n
- Performance Dissatisfiers
Harley Mustang
Lexus Loudness
Unusual NoisesTGW
Sound QualityTGR
KANO Model
+ Degree of Achievement
Basic Quality(Inhibitors)
Performance Quality(Attributes)
- CustomerSatisfactio
n
Exciting Quality(Surprise & Delight)
Axle Whine Wind Noise
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Introduction to NVHWhy Design for NVH?
• Customers place a high value on NVH performance in vehicles
• About 1/3 of all Product / Quality Complaints are NVH-related
• Often times, cost and weight targets prevent avoidance of NVH issues An example is a 2-pc driveshaft, which is less expensive, lighter, and has fewer joints than a 3-pc driveshaft, but has boom at a certain RPM. The 3-pc driveshaft does not demonstrate the boom.
What do you do???• NVH countermeasures CAN work harmoniously within the system as long as they are
DESIGNED INTO the system from the beginning.How do I go about doing it?
– Get management buy-in. Costs for NVH countermeasures are never put into programs early enough. This needs to change to ensure success.
– Run CAE early, using the best simulations available. Determine the frequency range and driving mode. Trust your CAE.
– Develop NVH countermeasures and make sure they are on the first phase of prototype vehicles (NOT the last)
– In this case, a torsional damper on the rear of the driveshaft solves the issue, but interferes with the fuel tank
– Since packaging studies were run early, the fuel tank was modified prior to hard tooling to provide clearance for the damper.
• Result– A well-packaged driveshaft which is lighter, less expensive, and more durable than
the alternate design, which fully satisfies all customer and corporate requirements.
Heuristic: NVH is always a late guest to the party. Plan countermeasures ahead to ensure you have enough energy, time and tools to entertain your guest!
NVH: Cost & Weight Considerations
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Introduction to NVHWhy Design for NVH?
• About 1/5 of all Warranty costs are NVH-related– Dealers may spend many hours to determine
source of NVH problem– Dealers 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
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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
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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)
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• 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
Design For NVH Heuristics
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• Don't confuse the functioning of the parts with 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 vehicle designs require the ability to develop requirements for the parts by cascading functional requirements from the system.
Design For NVH Heuristics
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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
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• 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
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DFNVH Process Flow and Target Cascade Noise Reduction Strategy: Targets are set for the noise
reduction capability of the sound package.
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DFNVH Process Flow and Target Cascade
Systems Engineering “V” and PD Process Timing
Define Req’s
Cascade Targets & Iterate
Optimize
Verify & Optimize
ConfirmVehicle (VDS - P/T NVH etc)
System (SDS - Force, Sensitivity,...)
Subsystem (Stiffness,...)
Components SDS
CustomerSatisfaction
PS PA CPPRSCKOO
CustomerWants/Needs
J1
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Trade-Off Loop
Perform Iterations Until Assumptions Comparable
System/Sub-System Assumptions
McPherson vs. SLA, etc.
Requires Hardware Parametric Model
Vehicle Assumptions Fixed
SLA or MacPherson Strut Suspension
Vehicle Level Target Ranges
Subjective (1-10) and Objective
Program Specific Wants
PALS (QFD, VOC, etc.)
Functional Images for Segment - R202
Preliminary Target Ranges
Future Functional Attribute Targets
Objective Target Ranges - VDS
Affordable Business Structure (ABS)
SISystem & Sub-System
Targets
Force or P/F Targets Determined with Parametric Models
Component End Item Targets
Component Resonant Frequencies, etc.
Design Optimization
CAE Optimization
Hardware Development
PA
Trade-Offs Flow Chart
Is Gross Architecture Feasible? Development
DFNVH Process Flow and Target Cascade
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DFNVH Process Flow and Target Cascade
NVH Functional Attribute
Sub -Attributes
Road P/TWind Brake Comp. S.Q. S&R Pass-by Noise (Reg.)
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DFNVH Process Flow and Target Cascade
Convert attribute target strategy to objective targets
POWERTRAIN NVH
IDLE NVHACCELERATION
NVH
CRUISE NVHDECELERATION
NVH
STEERING NVH
AUTOMATIC TRANS. SHIFT
NVH
TIP-IN / TIP OUT NVH
TAKE-OFF DRIVEAWAY
NVH
ENGINE START UP / SHUT OFF
NVH
TRANSIENTS NVH
ACCELERATION WOT
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DFNVH Process Flow and Target Cascade
CUSTOMER PERCEIVED P/T NVH
AIRBORNE NOISE STRUCTURE-BORNE NOISE
P/T RADIATED NOISE
AIRBORNE NOISE REDUCTION
BODY ACOUSTIC SENSITIVITY
MOUNT FORCES
P/T VIBRATIONMOUNT
DYNAMIC STIFFNESS
Acceleration NVH Target Cascade
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DFNVH Process Flow and Target Cascade
NVH Classification Parameters •Operating Condition (idle, acceleration, cruise on a rough road, braking, wind…)•Phenomenon (boom, shake, noise…) this is strongly affected by the frequency of the noise and vibration or input. •Source (powertrain, road, wind ..etc) •Classifying NVH problems provides a guidance for design, for example: low frequency problems such as shake historically involve major structural components such as cross members and joints.
DFNVH Process Flow and Target Cascade
Operating Condition NVH Concerns
Idle Shake and boom due to engine torque.
Lugging Shake and boom due to engine torque.
Wide Open Throttle (WOT)
Noise and vibration due to engine, driveline, exhaust vibration, and radiated noise.
Cruise (smooth road) Shake, roughness, and boom due to tire and powertrain imbalance and tire force variation, wind noise, and tire noise. Transmission and Axle whine.
Cruise (rough road) Road noise and shake
Tip-in "Moan" due to powertrain bending.
Braking Squeal, grind, moan and shudder.
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DFNVH Process Flow and Target Cascade
•The customer’s 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.
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DFNVH Process Flow and Target Cascade
NVH Aspect Subjective Response
Boom Low frequency sound 20 - 100 hz.
Drone Large amplitude pure tone in the region 100-200 hz
Growl Modulated low/medium frequency broad band noise 100-1000 hz
Groan Transient broadband noise with noticeable time variation and tone content, 50-250 hz
Moan A sound in the 80 to 200 Hz range, frequently consisting of one or two tones
Squeak High pitched broadband transient noise.
Whine Mid-frequency to high frequency pure tone (possibly with harmonics), 200-2000 hz
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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 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.•NVH from audio system interaction is also important with pulse width modulated signals for loads that couple with audio speakers.
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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
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DFNVH Process FundamentalsSource-Path-
Responder
SensitivityExcitation Response
• Engine Firing Pulses• Driveshaft Imbalance• Rough Road• Tire Imbalance• Speed Bump• Gear Meshing• Body-Shape Induced
Vortices• Brake Roughness
Excitation Source Examples:
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DFNVH Process FundamentalsSource-Path-
Responder
SensitivityExcitation Response
Tendency of the path to transmit energy from the source to the responder, commonly referred to as the transfer function of the system
Sensitivity:
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DFNVH Process FundamentalsSource-Path-
ResponderExample: Body Sensitivity
Tactile
∙ Point mobility (v/F) (Structural velocity / induced by force)
Acoustic
∙ Airborne (p/p)(Airborne sound pressure induced / by pressure waves)
∙ Structure-borne (p/F)(Airborne sound pressure / induced by force)
F (N)
V (mm/s)
p (dB)
Force Inputat Driving Point
Vibration Velocityat Driving Point
Interior SoundPressureSTRUCTURE
p (dB)
p (dB)
Interior SoundPressureSTRUCTURE
Airborne Noise
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DFNVH Process FundamentalsSource-Path-
ResponderBody Sensitivity Demonstration
Point Mobility Typical Point Mobility Spectrum for Compliant and Stiff Structures
Poi
nt M
obil
ity
(V/F
)
MoreCompliant
LessCompliant
Frequency ( f )50
140
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DFNVH Process FundamentalsSource-Path-
Responder
Subjective(customer perception)• S/W Shake (vertical)• S/W Nibble (rotational)• Seat Track (non-specific)
Objective (measurable)• S/W Shake• S/W Nibble• Seat Track (Triax) • Spindle Fore/Aft• Tie Rod Lateral
Response:
SensitivityExcitation Response
S/W = Steering Wheel
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DFNVH Process FundamentalsSource-Path-
Responder
Air
born
e P
/T
NV
HS
truc
ture
-bor
ne P
/T
NV
H
Tailpipe
Intake Orifice
Engine RadiatedSound
Active EngineVibration(X, Y, Z)
Active ExhaustVibration(X, Y, Z)
Body AcousticAttenuation (dB)
Body AcousticAttenuation (dB)
MountStiffness (N/mm)
Body AcousticSensitivity
MountStiffness (N/mm)
Body AcousticSensitivity
Driver Right Ear(dBA)
Air
born
e N
VH
Str
uctu
re-b
orne
NV
H
Powertrain Noise Model
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DFNVH Process FundamentalsSource-Path-
ResponderRoad Noise (P)
Chassis Forces to Body (F)
NPA
Body/Frame Sensitivity (P/F)
+ SuspensionForce Isolation
Tire/Wheel Forces
Suspension/Frame Modes
Suspension/Frame Design Parameters
Tire/Wheel Modes &Design Parameters
Body Modes
Body Design Parameters
Sub-structuring Modal Analysis (MA)
MATire/Road Force
Transfer Function
+
Road Profile
Road Noise Model
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DFNVH Process FundamentalsSource-Path-
Responder
Driveline Model
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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
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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)
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DFNVH Process FundamentalsSound Quality
The Sound Quality Process
1. Measurement (recording)2. Subjective evaluation (listening studies)
• Actual or surrogate customers3. Objective analysis
• Sound quality Metrics4. Subjective/Objective correlation5. Component design for sound quality
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DFNVH Process FundamentalsSound Quality
Binaural Acoustic “Achen Heads”
Stereo Sound Recording representing sound wave interaction with a partial human torso
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DFNVH Process FundamentalsSound Quality
Sound Quality Listening Room
Used for Customer Listening Clinics.
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DFNVH Process FundamentalsSound Quality
Poor Sound Quality Good Sound Quality
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DFNVH Process FundamentalsSound Quality
Quantifying Door Closing Sound Quality
1. Sound Level (Loudness)
2. Frequency Content (Sharpness)
3. Temporal Behavior
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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.
DFNVH Process FundamentalsSound Quality
Example: Qualifying Door Closing Sound Quality
Good Bad
Level (dBa) (color)
Fre
quen
cy (
Hz)
(y-
axis
)
Time (sec.) (x-axis)
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DFNVH Process FundamentalsSound Quality
Design for Sound QualityDoor Closing Example
Perceived Sound
Structure-borne Airborne
Seal Trans Loss
Latch Forces Str. Compliance
Inertia Spring Rates Material
Radiated Snd.
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
DFNVH Process FundamentalsSound Quality
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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
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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
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NVH Design Principles
Tube Inlet/Outlet Noise
ExcitationSource, Energy
Input
StructureSensitivity
Customer
Air
born
e N
VH
Stru
ctur
e-bo
rne
NV
H
Air Impingement Noise
Source Path Responder
Impactive Noise
Radiated/Shell Noise Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
EnvironmentSensitivity
IsolationStiffness
IsolationDamping
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NVH Design Principles
Tube Inlet/Outlet Noise
ExcitationSource, Energy
Input
StructureSensitivity
Customer
Air
born
e N
VH
Stru
ctur
e-bo
rne
NV
H
Air Impingement Noise
Source Path Responder
Impactive Noise
Radiated/Shell Noise Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
EnvironmentSensitivity
IsolationStiffness
IsolationDamping
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Mechanism:
• Structural surface vibration imparts mechanical energy into an adjacent acoustic fluid in the form of pressure waves at same frequency 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
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Design Action(s):
• Stiffen: Add ribbing, increase gage thickness, change material to one with higher elastic modulus, and add internal structural supports
• Minimize surface area: Try to avoid 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
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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
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Design action(s):• Make tubes as straight as possible• Include an in-line silencer element with sufficient
volume (muffler)• Locate inlet/outlet as far away from customer as
possible• Design for symmetrical (equal length) branches
Design Principles – Airborne NVHTube Inlet/Outlet Airflow Noise
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Design Principles – Airborne NVHTube Inlet/Outlet Airflow Noise
V6 Intake Manifolds
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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
Design Principles – Airborne NVHImpactive Noise
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Design Principles – Airborne NVHImpactive Noise
Air Pumping
Air forced in and out of voids is called “air pumping”
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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)
Design Principles – Airborne NVHImpactive Noise
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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
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Design action(s):• Design fan blades asymmetrically, with
circumferential ring• Optimize fan diameter and flow to achieve lowest
broad band noise• Use fan shroud to guide the incoming and outgoing
airflow
Design Principles – Airborne NVHAir Impingement Noise
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NVH Design Principles
Tube Inlet/Outlet Noise
ExcitationSource, Energy
Input
StructureSensitivity
Customer
Air
born
e N
VH
Str
uctu
re-b
orn
eN
VH
Air Impingement Noise
Source Path Responder
Impactive Noise
Radiated/Shell Noise Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
EnvironmentSensitivity
IsolationStiffness
IsolationDamping
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Design Principles – Airborne NVHAirborne Noise Path Treatment
Noise Reduction
EngineCompartment
Absorption
Body & Insulator Blocking(Panels)
Pass-Thru Sealing
(Components)
InteriorAbsorption
*
Design principle(s):• Eliminate noise source• 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
Design Principles – Airborne NVHAirborne Noise Path Treatment
*
air absorption materials
Design Principles – Airborne NVHAirborne Noise Path Treatment
• Barrier performance is controlled mainly by mass– 3 dB improvement requires
41% increase in weight
• Mastic or laminated steel improves low frequency sound quality
• Soft decoupled layers (10-30 mm) absorb sound
• Pass-thru penetration seals are weaker than steel
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NVH Design Principles
Tube Inlet/Outlet Noise
ExcitationSource, Energy
Input
StructureSensitivity
Customer
Air
born
e N
VH
Stru
ctur
e-bo
rne
NV
H
Air Impingement Noise
Source Path Responder
Impactive Noise
Radiated/Shell Noise Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
EnvironmentSensitivity
IsolationStiffness
IsolationDamping
*
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
Design Principles – Airborne NVHAirborne Noise Responder
Treatment
*
NVH Design Principles
Tube Inlet/Outlet Noise
ExcitationSource, Energy
Input
StructureSensitivity
Customer
Air
born
e N
VH
Stru
ctur
e-bo
rne
NV
H
Air Impingement Noise
Source Path Responder
Impactive Noise
Radiated/Shell Noise Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
EnvironmentSensitivity
IsolationStiffness
IsolationDamping
*
• 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 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 NVH
The steering column vibration will have an extra large peak if the steering column mode coincides with the overall bending mode.
*
Design Principles – Structureborne NVH
● Powertrain modes need to be separated from the 1st and 2nd body bending and torsion modes by at least 2Hz.
● Cowl and cross car beam modes must be separated from steering column modes by as much as possible (minimum of 1Hz)
Natural frequencies of major structures need to be separated to avoid magnification.
*
In addition to adopting modal separation strategies, other principles are listed below:
• Reduce excitation sources• Increase isolation as much as possible• Reduce sensitivity of structural response.
Design Principles – Structureborne NVH
*
NVH Design Principles
Tube Inlet/Outlet Noise
ExcitationSource, Energy
Input
StructureSensitivity
Customer
Air
born
e N
VH
Stru
ctur
e-bo
rne
NV
H
Air Impingement Noise
Source Path Responder
Impactive Noise
Radiated/Shell Noise Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
EnvironmentSensitivity
IsolationStiffness
IsolationDamping
*
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 (shock towers, frame mounting points, or subframe mounting points)
Design Principles – Structureborne NVHExcitation Source
*
Design Principles – Structureborne NVHExcitation Source
A/C Compressor – Bad Example
Cantilever Effect → Less Rigid
*
Design Principles – Structureborne NVHExcitation Source
A/C Compressor - Good Example
Design Principles – Structureborne NVHExcitation Source
Example: Axle Whine
Characteristics:- Tonal noise 300 - 800 Hz- Occurs between 40 - 70 mph in drive or coast modes under moderate to wide open throttle.- Frequency = # Pinion teeth x Driveshaft Speed in RPM / 60.- Caused by gear transmission error (TE), which is the difference between the actual position of the output gear and the position of a theoretical or “perfect gear”, measured in “arc-second”.
Design Principles – Structureborne NVHExcitation Source
Requirement Cascade- Vehicle level: Driver audible target in dB(A) and 0.5 micron pinion nose vibration.- System level: 12 arc-sec.
- Component level: 7 arc-sec at nominal mesh position (single flank).Noise factors:
- Manufacturing: gear cutting, heat treat and lapping variation.
- Assembly: Pinion and differential shiming - Gear mesh deflection, gear wear
- Driveline modal response (torsional and bending modes)
Development Flow- <Program Target Confirmed> Define “health chart” Axle whine cascade
(CAE).- <M1 Design Judgment> Verify targets are compatible (CAE)- <Final Design Judgment> Single Flank TE, Axle TE and Vehicle NVH
measurements
Options to reduce whine at the source- Increase contact ratio.
- Fine tooth combination
- Long tooth face width
- More spiral angle
- Reduce gear mesh deflection- Increase component stiffness (bearings, differential case, carrier).
- Reduce gear wear- Reduce input torque, sliding velocity
- Improve lubrication
- Reduce gear manufacturing tolerance.- 3D hypoid gear hobbing is industry standard for high volume automotive
applications.
- Reduce tolerance on hard finishing (lapping).
- Reduce assembly tolerances for pinion and ring gear mounting distances.- Measure gap and shim to compensate (build to pattern).
- Use threaded adjuster to position ring gear in proper mesh
- Measure all components critical dimensions prior to assembly and shim to
achieve proper stack (build to position).
-
Design Principles – Structureborne NVHExcitation Source
*
NVH Design Principles
Tube Inlet/Outlet Noise
ExcitationSource, Energy
Input
StructureSensitivity
Customer
Air
born
e N
VH
Stru
ctur
e-bo
rne
NV
H
Air Impingement Noise
Source Path Responder
Impactive Noise
Radiated/Shell Noise Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
EnvironmentSensitivity
IsolationStiffness
IsolationDamping
*
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 loss
• If nothing else works or is available, use dead mass as tuning mechanism.
Design Principles – Structureborne NVHPath - Isolation Strategy
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Design Principles – Structureborne NVHPath - Isolation Strategy
Tuning and Degree of IsolationBy moving natural frequency down for this system it increased damping at 100 Hz
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NVH Design Principles
Tube Inlet/Outlet Noise
ExcitationSource, Energy
Input
StructureSensitivity
Customer
Air
born
e N
VH
Stru
ctur
e-bo
rne
NV
H
Air Impingement Noise
Source Path Responder
Impactive Noise
Radiated/Shell Noise Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
Acoustic Attenuation
EnvironmentSensitivity
IsolationStiffness
IsolationDamping
*
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
Design Principles – Structureborne NVHStructure Sensitivity Strategy
*
Design action(s):• Select architecture that can provide the maximum
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
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
Design Principles – Structureborne NVHStructure Sensitivity Strategy
Body Modes and Body Architecture
*
Design Principles – Structureborne NVHStructure Sensitivity Strategy
Body Modes and Body Architecture
*
Design Principles – Structureborne NVHStructure Sensitivity Strategy
Body Modes and Body Architecture
*
Design Principles – Structureborne NVHStructure Sensitivity Strategy
Body Modes and Mass DistributionEffect 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.
*
l 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
Design 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 Strategy
Guideline: 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.
Guiding Heuristic - Know what to get right first and what can be tuned later
Design Principles – Structureborne NVHStructure Sensitivity Strategy
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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
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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.
*
Wind Noise Target Cascade Diagram
Vehicle level Wind Noise
Excitation Sources
Antenna / Accessori
esMirror Shape
Green House Shap
e
Open Windows
/ Sunroof
Seals
Aspiration Leak
s
Transmission Los
s
Glass / Panels
Static Sealin
gDynamic Sealing
Door System Stiffness
Wind Noise Example
*
Wind Noise Example
*
Aerodynamic excitation
• A-pillar vortex• Mirror wake• Antenna vortex• Wiper turbulence• Windshield turbulence• Leaf screen turbulence• Windshield molding
turbulence
• Exterior ornamentation turbulence
• Cavity resonances• Air flow induced panel
resonances• Air extractor noise ingress• Door seal gaps, margins
and offsets
Wind Noise Example
*
Aspiration leakage
• Dynamic sealing– Closures
• Dynamic weatherstrip• Glass runs• Beltline seals• Drain holes
– Moon roof• Glass runs
– Back-lite 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
Wind Noise Example
*
• 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
Design For NVH (DFNVH)
*
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 structure 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 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.
*
Design For NVH 2002 Mercury
Mountaineer “Aachen Head” was used to improve Mountaineer’s 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.
NVH in EVs• NVH perceived quality and characteristics inherent to vehicle
branding have been well defined and tuned over the years, based on combustion engine sound sources.
• With the evolution of electric vehicles, however, this applied NVH knowledge has unfortunately not translated well to electric vehicles. ➢ Customer expectations for electric vehicle sound quality
have not been well defined. ➢ The lack of refined requirements, coupled with more
stringent environmental and federal regulations, has made it difficult for NVH engineers to tune to their system attribute.
➢ Is NO pass-by noise acceptable? What about pedestrians, who may inadvertently step in front of an oncoming EV?
*
NVH in Evs (Cont.)
• Based on new sound sources, it is necessary to➢ Review the foundation diagrams to understand system
interactions, and external factors➢ Conduct customer research to determine customer
expectations for sound quality and powertrain NVH➢ Develop targets based on customer feedback.
*
Electrical Noise Prevention for Internal Combustion and emerging
Electric VehiclesAEV 5070 Class Presentation
M. Lunn
Customer Expectation of Vehicles – SE Requirements – Quiet, Green with features• Requirement of customer for any vehicle is quiet
and no “unassociated” noises or undesirable noises
• Fuel Economy for IC engines and Effective Range for EV’s wants efficient use of power, rule of thumb is 0.04 mpg/A.
• Features to heat interior, operate lighting, cool engine area(EV’s have cooling fans and liquid cooled electronics also), blow air in interior, pump fuel and control suspension use electrical power.
Electrical power control – Pulse Width Modulation challenges no noise!
• Inefficient power control is a A/C blower motor with variable motor control. DC current to a motor sinks voltage in a MOSFET load(waste). Excess energy is sunk to limit speed, heat is excess from engine for IC.
• Efficient power control is Pulse Width modulated heater(PTC heating elements like toaster) with no wasted energy and PWM motor control.
• Pulse Wi is a square wave signal for power with variable duty cycle(positive time/ period), allows variable control. Try an example on next slide!
Example of Electrical control – DC and AC simulation – Sine waves shown.
Packaging diagram of PWM signals with audio noise issue on heated seatsNote corouting of PWM heated seats with audio
Single ended PWM Load on the heated seatsIs issue.Prior to schematics or Package any single circuitWith PWM current over ___ Amps is suspectFor noise to audio.Analysis is easy, if PWMEnters the body withAudio then its possible toHave noise
How noise is induced on a device or wires by a PWM or time varying signal
As built route to right side, separate power and and ground, noise heard
Top Yellow signal is current probe on the heated seats at 10 mV/A and range of 9.3 A, Delta time is 200 HZ, 5 ms.
Bottom is LH front speaker wires with noise pulse on rise and falls of the current. This is on line level output, through the ANC, then on speaker amplified by AMP.
As built route to right side, separate power and ground, noise heard
• Heated seat current is on the audio speaker as shown.
PWM square waves are sum of Sine waves – these make noise!
Systems Engineering V – how to prevent noise issues?
• These noise issues are usually detected late in vehicle testing, how to do early in development?
• The single V does not use the analysis early tofind noises fromexperience, fixedin late changes Is pattern.Better to preventIn design left sidevs. V&V on right side!
How to Prevent noise issues – how to implement?
• A double V approach is a solution – requires the CAE analytical modeling tools be used, time provided and staffing supported to allow application and prevent.– This is not a practice I see in the industry but electrical CAE
and EMC tools are capable! (Mentor, Dassault, etc.• Why not adopt these tools?
– Data for circuits, components and loads in the environment of in house, regional and supplier designs does with staffing, time provided does not allow these tools to be used.
• Most solutions are fast to implement if program supports cost/vehicle needed.– Cost less overall than the analytical approach???
Package Diagram of PWM signals with prevent action – no noise heard
• The PWM load is twisted with power to get out of the audio circuit path and cancel fields.
LH routing and twisted power and ground – no noise heard
Same top yellow trace for current probe at 10mV/A and 10.8 A, 200 Hz.
LH speaker shows almost no noise on the speaker circuits! No noise heard by customer.
LH routing and twisted power and ground – no noise heard
• CHB purple LH speaker is very low, not following current.
Overlay on engine compartment – no no noise heard and heated seats on
• CHA yellow is seat current, CHB purple is not used.
Overlay on engine compartment – no no noise heard and heated seats on
- First(200), third(600) and fifth(1000) harmonics shown.
Why is this significant to EV’s in future!• PWM Loads are increasing for EV’s from IC vehicles!
IC engine EV future FrequencyCooling fans – relay power 600W PWM 200 W20kHz above audioPower Steering- 1000 W peak 1000 W peak 20KHz above audio(audible harmonic in the AM and FM band on any car I know of!)Heated seats - 120 W 120 W 200 Hz audio and AMHeated interior – 900 W constant 900W constant 100 Hz in Audio and AM(within 12 inches of audio unit for inverse squared 1/r^2 relationship of fields !!)Active Suspension - 9A/108W) 9A/108W) 1000 Hz (TBD as of yet)Fuel Pump(ERHV) - 10A 10A 9600 Hz in audio, AM, FMStart/Stop on Engine – large changes large changes pulse but spikes heardA/C load - 10 A for comp clutch 50 A for compressor (TBD)
• Not using PWM will increase loads and decrease range of batteries or fuel economy! Approximately 0.04 MPG per A and range anxiety.
• Have you been in an EV or start/stop IC vehicle, noticed the only sound can be a tire noise on surface and brake caliper release! Switch travel is noise! Transition to rolling or start and you have pulse of current, potential noise.
Requirements of Vehicle designs on noise and EMC with Fuel Economy increases
• Vehicles for IC engines have been mostly sheet metal for cost and forming, assembly.– Also provides ground plane and E field shielding!!– Works until fuel economy goes to 54.5 MPG
• To support future MPG rules the weight and structure may change to alternatives– Aluminum is not as good a ground or shield in a body
construction.– Plastic or carbon fiber is not conductive or a shield.
All the alternatives make electrical interactions harder to prevent and more expensive!!
http://www.bloomberg.com/news/2011-06-14/bmw-carbon-lets-vehicles-follow-bicycle-road-to-lightness-cars.html
Questions & References and links• PHET AC and DC circuits:
http://phet.colorado.edu/en/simulation/circuit-construction-kit-ac-virtual-lab
• PHET Faradays Electromagnetic lab: http://phet.colorado.edu/en/simulation/faraday
• PHET Fourier: making waves: http://phet.colorado.edu/en/simulation/fourier
• All PHET Simulations, these are very useful and free - http://phet.colorado.edu/
• Also of interest for general knowledge and explainations - http://www.khanacademy.orgAlso of interest for general knowledge and explainations - http://www.khanacademy.org/
• I use these to explain ideas and issues vs. lots of words and “you don’t understand this”. Try with your kids!
*
• 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
*
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
*
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