1. NVH Category NVH Characteristic Frequency (Hz) Ride < 5
Steady State Frequency Response
Ride < 5
Shake
Boom
Moan
Structural Borne Noise 150 – 500
Air Borne Noise > 500
Transient Response
Harshness

2. Single Degree of Freedom
Control by
Dynamic
Stiffness
Mass
Damping
Isolation Region fn
* fn

3. Dynamic Stiffness Dynamic Stiffness: (K - m ω2) – j C ω
(K - m ω2)2 + (C ω)2
Mass M
ω = 2* π*f
f is the frequency
Stiffness K
Damping C

4. Pure Tone Sound at a single frequency Sound Pressure dB dBA
Objective measurement dB
Logarithmic of sound pressure
dBA
A-Weighted to adjust for ear sensitivity

5. Human Sensitivity More constant across frequency range with velocity
Hearing range 20 – 2000 Hz
Depends on overall level
Sound at one frequency may mask by other frequencies
Depends on age, sex and other factors

6. Tactile Response Subjective-Objective
Acceleration
Frequency
SR = 6
SR = 5

7. Tactile Response Subjective-Objective (2)
Velocity
Frequency
SR = 6
SR = 5

8. Sound Pressure Level and A Weighting

9. NVH Classification Operating Condition Subjective Evaluation
Idle, Low Speed, Cruising, POT, WOT
Subjective Evaluation
Shake, Boom, Noise, Harshness
Objective Measurement
Sound Pressure, Acceleration
Frequency Range
Source
Powertrain, Road, Exhaust

10. NVH Subjective Rating
Most
Targets
No Sale

11. NVH Objectives Assess vehicle responses relative to design targets:
Tactile responses
Seat track
Steering column
Toe pan
Acoustic responses
Driver’s ear
Front Passenger’s ear
Rear passenger’s ear

12. Shake 5 – 40 Hz Idle Shake Isolated Road Shake Rough Road Shake
Smooth Road Shake
Wheel/Tire Imbalance
Tire Force Variation

13. Design For Shake Body vertical, lateral bending and torsion modes
Front end bending and torsion modes
Front floor modes
Steering column modes
Seat modes
Avoid stickiness of the shock and CV joints that causes high force input and resonance in smooth road shake

14. Design For Shake (2)
Mode separation and mode shape management of engine bounce, roll, pitch and yaw rigid body modes

15. Boom Hz
Idle Boom
Isolated Road Boom
Rough Road Boom

16. Body Design for Boom 1st and 2nd fore-aft acoustic modes
Body 1st and 2nd order vertical bending
Front floor vertical bending
Dash panel fore-aft bending
Quarter panel bending
Fuel tank bounce
Spare tire tub bounce
Decklid, liftgate or lower back panel pumping

17. Structural Borne NoiseHz
Powertrain Noise
Rough Road Noise
Gear Whine

18. Design For Noise
Most of the vibration energy imparted to the vehicle is below 150 Hz.
Below 150 Hz:
Body structure is important for controlling noise and vibration
Lack of structure usually results in costly design and tooling changes
Above 150 Hz:
Can be resolved with relatively simple structure modifications, such as bead patterns, or damping treatments.

19. Design For Noise (2) Powertrain Bending Isolation
Powertrain Bracket Isolation

20. Modal Chart CHASSIS/POWERTRAIN MODES BODY/ACOUSTIC MODES
Suspension Hop and Tramp Modes
Ride Modes
Suspension Longitudinal Modes
Powertrain Modes
Exhaust Modes 5 10 15 20 25 30 35 40 45 50 Hz
BODY/ACOUSTIC MODES
Body First Torsion (25Hz)
Steering Column First Vertical Bending (29Hz)
Body First Bending (22Hz)
First F/A Acoustic Modes (48Hz) 5 10 15 20 25 30 35 40 45 50 Hz
EXCITATION SOURCES
Inherent Excitations (General Road Spectrum, Reciprocating Unbalance, Gas Torque, etc.)
Process Variation Excitations (Engine, Driveline, Accessory, Wheel/Tire Unbalances)
V8 Idle ( RPM)
Hot Cold
First Order Wheel/Tire Unbalance (5-75MPH) 5 10 15 20 25 30 35 40 45 50 Hz

21. Body-in-White Targets
Static Stiffness
Bending
Torsion
Normal Modes
Vertical bending
Lateral bending

22. Trimmed Body Targets Normal Modes Vertical bending Torsion
Lateral bending
Front end bending
Front end torsion

23. Instrument Panel/Column Targets
Normal Modes
Vertical bending
Lateral bending

24. Seat Targets Normal Modes Different row may have different target
On Bedplate
Fore aft
Lateral
In Vehicle
Different row may have different target

25. Idle Load

26. Idle Torque   r h 
Pbore
Pcrank
mrecip
arecip L

27. Piston Displacement   r h 
Pbore
Pcrank
mrecip
arecip L

28. Trigonometric Derivatives  r h 
Pbore
Pcrank
mrecip
recip L

29. Piston Velocity   r h 
Pbore
Pcrank
mrecip
arecip L

30. Piston Acceleration   r h 
Pbore
Pcrank
mrecip
arecip L

31. Smooth Road Shake

32. Wheel/Tire Imbalance Definition
Simulation
Shake caused by the unbalanced inertia forces from the high speed rotation of the unbalanced wheel in vehicle cruising
Load
1.0 oz-inch (Sensitivity) unbalanced force at the spindles
Both vertical and fore-aft loads with vertical load trailing fore-aft load by 90 degrees
Applications
Front wheel in-phase, Front wheel out-of-phase, Rear wheel in-phase and Rear wheel out-of-phase

33. Wheel/Tire Imbalance Calculation
F = mr2
F is imbalance Force (N)
m is imbalance mass (Mg)
r is imbalance radius (mm)
 is rotation speed (rad/sec)
F = 1.0 oz-in = 1.0 * 28.3 * 10-6 (Mg/oz) * 25.4 (mm/inch) * 4 * 2 * f2 = * f2 (N)
f is frequency (cycles/sec)

34. Wheel/Tire Imbalance Speed Map
The wheel/tire speed map (frequency v.s. vehicle speed) is dependent on the wheel/tire size, the wheel/tire stiffness and the payload
V = 2 * π * Tire Effective Radius * Frequency
However, the Frequency/Vehicle Speed(MPH) is typically around 0.2
Based on the above assumption, the frequency range of interest from 25 MPH to 125 MPH is
5 Hz to 25 Hz

35. Tire Force Variation Definition
Simulation
Shake caused by the variation of the radial stiffness of the tires
Load
1.0 lbf (Sensitivity) variation force at the spindles
Vertical load only
Applications
Front wheel in-phase, Front wheel out-of-phase, Rear wheel in-phase and Rear wheel out-of-phase

36. Tire Force Variation Speed Map
The wheel/tire speed map (frequency v.s. vehicle speed) is dependent on the wheel/tire size, the wheel/tire stiffness and the payload
V = 2 * π * Tire Effective Radius * Frequency
However, the Frequency/Vehicle Speed(MPH) is typically around 0.2
Based on the above assumption, the frequency ranges of interest from 25 MPH to 125 MPH are
First Order : 5 Hz to 25 Hz
Second Order : 10 Hz to 50 Hz

37. Rough Road Noise

38. Spatial PSD Road Profile
Spatial Frequency ( Cycles / mm)
Wave number
1 / wavelength
PSD Amplitude (mm^2 / (cycles / mm))
Power Regression Analysis (Y = * X )