Student Guide
Noise, Vibration, and HarshnessNVH
SAFETY NOTICE
warnings cautions notes
warnings cautions
Notes
Cautions warnings
Noise, Vibration, and Harshness i
TABLE OF CONTENTSINTRODUCTION 1OBJECTIVES 1ACRONYMS 2LESSON 1 EVALUATING NVH CONCERNS 5
PRELIMINARY INFORMATION 5Pre-road Test Inspection 7Vehicle Road Test 8Road Test Methods 9Diagnostic Worksheet Page 1 10Diagnostic Worksheet Page 2 11
LESSON 2 DIAGNOSING WHEEL AND TIRE VIBRATION 13WHEELS AND TIRES 13NVH TERMS AND THEORY 14
Vibration Order 15Cycle 16Frequency 17Amplitude 18Resonance 19
NVH MEASURING TOOLS 20Sirometer 20Electronic Vibration Analyzer (EVA) 21MTS 4100 22
ROAD TESTING FOR RESULTS 23Slow Acceleration Test 23Neutral Coast Down Speed Test 23Calculating Wheel and Tire Frequency 24Frequency Related Component Group 25Wheel and Tire Balance 26Radial Force 27Radial Force Variation 28
MEASURING WHEEL AND TIRE RUNOUT 29System Radial Runout 30Radial Runout 31Lateral Tire Runout 32
35 35
Road Testing 36
ii Noise, Vibration, and Harshness
Slow Acceleration and Neutral Coast Down 36Driveline Vibrations 37Propeller Shafts 38Propeller Shaft Runout 39Calculating the Propeller Shaft Frequency 40Driveline Operating Angles 42Propeller Shaft Operating Angle 43Measuring Operating Angles 44Transmission Yoke Measurement 45Propeller Shaft Measurement 46Pinion Flange Measurement 47
48Engine-Speed Vibration 48Engine Frequency Formula 49First- and Second-order Engine Vibration 50First-order Vibration 50Torque Converter 50Second-order Vibration 51Half-order Engine Vibration 51Engine Firing Frequency 51Compelling Force of Exhaust 52Engine Accessory Vibration 53Calculating Engine Accessory Frequency 54
LESSON 4 DIAGNOSING NOISE 57GENERATION OF NOISE 57
Droning Noise 57Tire Noise 58Differential Noise 59Growl Noise 60Howl Noise 61Road Testing 62Telegraphing 63Using the ChassisEAR 64Attaching the Sensors 65
LESSON 5 HARSHNESS 67HARSHNESS 67
Suspension Components 67
69
Noise, Vibration, and Harshness iii
GLOSSARY 71 75
75ROAD TEST METHODS 76
Road Test Tips 76ROAD TESTING 76
Slow Acceleration Test 77Neutral Coast Down Speed Test 77Downshift Speed Test 77Torque Converter Test 78Steering Input Test 1 78Steering Input Test 2 78Neutral Run-up Test 79Engine Loaded Test 79Engine Accessory Test 80
!! 81!! 82"# 84
Engine-speed Frequency 84Engine Frequency 84Engine Accessory Frequency 84
!"# 85Vehicle Speed Frequency 85Tire and Wheel Group 85Propeller Shaft Group 86Propeller Shaft Balancing 87
COMPLETE FORMULAS 88Engine Vibration Formula 88Engine Accessory Formula 88Engine Firing Frequency Formula 88Propeller Shaft Frequency Formula 88
SHORT FORMULAS 89Engine Vibration Formula 89Engine Accessory Formula 89Engine Firing Frequency Formula 89Propeller Shaft Frequency Formula 89
iv Noise, Vibration, and Harshness
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Noise, Vibration, and Harshness 1
INTRODUCTION
This training course focuses on how to use a systematic approach to diagnose and repair the root
cause of vehicle noise, vibration, and harshness (NVH) concerns.
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problems to certain component groups. This course also provides the ability to apply the theory of
NVH to isolate a component as the cause.
The primary sources of NVH concerns are generated by the following component groups:
= Tire and wheel
= Driveline
= Engine and torque converter
OBJECTIVES
Upon completion of this course, you will be able to:
= Perform a pre-road test inspection
= Identify road test methods
= Identify NVH diagnostic tools
= Apply diagnostic methods
= Classify the symptoms of NVH concerns
= Calculate component frequencies
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= Troubleshoot and repair NVH concerns
= Diagnose and repair wheel and tire vibrations
= Diagnose and repair driveline-related vibrations
= Diagnose and repair engine-related vibrations
2 Noise, Vibration, and Harshness
ACRONYMS
The following is a list of acronyms used throughout this publication:
= ABS Anti-lock Brake System
= AC Alternating Current
= CPS Cycle per Second
= CV Constant Velocity
= DRBIII Diagnostic Readout Box Third Generation
= DTC Diagnostic Trouble Code
= EVA Electronic Vibration Analyzer
= Hz Hertz
= NVH Noise, Vibration, and Harshness
= RFV Radial Force Variation
= RPM Revolutions per Minute
= SAE Society of Automotive Engineers
= SB Service Bulletin
Noise, Vibration, and Harshness 3
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4 Noise, Vibration, and Harshness
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Noise, Vibration, and Harshness 5
LESSON 1 EVALUATING NVH CONCERNS
PRELIMINARY INFORMATION
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8 Noise, Vibration, and Harshness
Vehicle Road Test
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Road Test Methods
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Note: Detailed instructions for these road tests are provided in the Appendix.
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Noise, Vibration, and Harshness 13
LESSON 2 DIAGNOSING WHEEL AND TIRE VIBRATION
WHEELS AND TIRES
Wheel-and tire-related vibrations occur at a relatively low frequency, typically 1015 Hz. This can
result in a vibration experienced at speeds usually above 40 mph. Even a small amount of wheel
imbalance can translate into a vibration problem.
Tires wear faster than other components; as a result customers frequently replace original tires
with different types and sizes. When the tires are replaced, the wrong tire might be selected.
Some of the contributing factors to wheel and tire vibration can be:
= Quality
= Excessive runout
= Non-uniformity
There are many sources of wheel and tire vibration some of the major sources are:
= Wheel and tire imbalance
= Condition of the wheels and tires
= Foreign debris in wheel
= Uniformity
= Tire dimensions
= Conicity
= Radial force variation
= Brake rotor
= Constant velocity (CV) shaft
= Hub
14 Noise, Vibration, and Harshness
NVH TERMS AND THEORY
When diagnosing a vehicle with a vibration concern, you must be able to obtain the frequency
of the vibration. Diagnostic equipment is necessary to diagnose and repair NVH concerns. A
technician must be able to measure the frequency of the vibration, and relate the frequency of a
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In addition to using the diagnostic equipment, it is important that a technician clearly recognize
NVH theory and how it can be applied to identify the cause of a customer concern.
There are common characteristics of noise and vibration used to diagnose NVH concerns. The
following terms and graphics help explain how the frequency of a noise or vibration is used to
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= Order
= Cycle
= Frequency
= Amplitude
= Resonance
Source
Transfer path
Responder
Noise, Vibration, and Harshness 15
1
2
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1 First-order Vibration
(One Disturbance per Revolution)
2 Second-order Vibration
(Two Disturbances per Revolution)
Figure 4 Vibration Order
Order is the number of disturbances created in one revolution of a component. A single high spot
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disturbance of 10 Hz.
If the tire developed a second high spot, a second-order disturbance would result. The wheel
rotating 10 times per second
