8/3/2019 Characteristics of NVH
1/26
Characteristics of NVHCharacteristics of NVH
8/3/2019 Characteristics of NVH
2/26
Audible Range ofAutomotiveAudible Range ofAutomotive
SoundsSo
unds
Automobiles have a full range of soundsAutomobiles have a full range of sounds
Low speed Drones, very low pitch and can beLow speed Drones, very low pitch and can be
felt but hardly heard.felt but hardly heard.
Brake Squeal, High pitch sound that can beBrake Squeal, High pitch sound that can be
heard but hardly felt.heard but hardly felt.
8/3/2019 Characteristics of NVH
3/26
8/3/2019 Characteristics of NVH
4/26
NoisesNoises
There are many noises that occur in anThere are many noises that occur in an
Automobile.Automobile.
The 4 main noises that a technician needsThe 4 main noises that a technician needsto be able to identify are;to be able to identify are;
DroningDroning
BeatBeat
Road NoiseRoad Noise
Brake SquealBrake Squeal
8/3/2019 Characteristics of NVH
5/26
DroningDroning
Adiscomfort in theAdiscomfort in the
ear caused by suddenear caused by sudden
changes inchanges in
atmosphericatmosphericpressure.pressure.
The three types ofThe three types of
droning are:droning are:
Low speed DroningLow speed Droning
Middle speed DroningMiddle speed Droning
High speed DroningHigh speed Droning
8/3/2019 Characteristics of NVH
6/26
All spee
ds of
droning consist of a non
All spee
ds of
droning consist of a non--directional, low pitched, and long duration noise.directional, low pitched, and long duration noise.
Low speed Droning; is hard to hear and feelsLow speed Droning; is hard to hear and feels
like pressure in the ears.like pressure in the ears.
High speed Droning; a humming noise that isHigh speed Droning; a humming noise that isuncomfortable to the ears.uncomfortable to the ears.
8/3/2019 Characteristics of NVH
7/26
Droning can occurDroning can occur
while accelerating orwhile accelerating or
decelerating, ordecelerating, or
through variousthrough variousengine or vehicleengine or vehicle
speeds.speeds.
8/3/2019 Characteristics of NVH
8/26
It is important for aIt is important for a
technician to pinpointtechnician to pinpoint
the vehicle speedthe vehicle speed
and/or engine speedand/or engine speedin which the NVHin which the NVH
concern occurs.concern occurs.
8/3/2019 Characteristics of NVH
9/26
Likely Causes of DroningLikely Causes of Droning
Bending resonance of exhaust pipes.Bending resonance of exhaust pipes.
Resonance of auxiliary equipment.Resonance of auxiliary equipment.
Bending resonance ofdrive shaft.Bending resonance ofdrive shaft. Resonance of suspension links.Resonance of suspension links.
Transmission of engine vibration.Transmission of engine vibration.
Transmission of exhaust noise.Transmission of exhaust noise. Transmission of intake air noise.Transmission of intake air noise.
8/3/2019 Characteristics of NVH
10/26
BeatBeat
Must have 2 sources.Must have 2 sources.
The sensation of aThe sensation of abeat sound is mostbeat sound is most
noticed when thenoticed when theFrequency differenceFrequency differenceis 1 to 6 Hz.is 1 to 6 Hz.
If two frequencies areIf two frequencies are
more than 6 Hz apart,more than 6 Hz apart,there sounds arethere sounds aredistinguishable fromdistinguishable fromeach other.each other.
8/3/2019 Characteristics of NVH
11/26
Likely Causes of a BeatLikely Causes of a Beat
Engine andAir Conditioning Compressor.Engine andAir Conditioning Compressor.
Engine and Power Steering HydraulicEngine and Power Steering Hydraulic
PumpPump Engine and vibration of the drive shaftEngine and vibration of the drive shaft
Tire nonTire non--uniformityuniformity
8/3/2019 Characteristics of NVH
12/26
Road NoiseRoad Noise The impact betweenThe impact between
the road surface andthe road surface andtires cause the tries totires cause the tries tovibrate.vibrate.
This vibration isThis vibration istransmitted to thetransmitted to thesuspension and body.suspension and body.
The resonanceThe resonance
characteristic of thecharacteristic of thepassengerpassengercompartmentcompartmentamplifies the roadamplifies the road
noise.
noise.
8/3/2019 Characteristics of NVH
13/26
Brake SquealBrake Squeal
The most common NVH Noise Concern.The most common NVH Noise Concern.
Drum Brakes; emit a lower pitched noiseDrum Brakes; emit a lower pitched noise
that gets louder with increased brakethat gets louder with increased brakepedal pressure.pedal pressure.
Disc Brakes; generally a high pitchedDisc Brakes; generally a high pitched
squeal that occurs with light pedalsqueal that occurs with light pedal
pressure.pressure.
8/3/2019 Characteristics of NVH
14/26
Likely Causes ofBrake SquealLikely Causes ofBrake Squeal
Worn Brake LiningsWorn Brake Linings
NonNon--uniform thickness of brake disc ofuniform thickness of brake disc of
drumdrum Excessive run outExcessive run out
Contamination of friction surfacesContamination of friction surfaces
Damaged brake liningsDamaged brake linings
8/3/2019 Characteristics of NVH
15/26
VibrationsVibrations
The main characteristics of vibrations are:The main characteristics of vibrations are:
Ride ComfortRide Comfort
ShakeShake ShimmyShimmy
Brake ShudderBrake Shudder
8/3/2019 Characteristics of NVH
16/26
Ride ComfortRide Comfort
When un sprung components start toWhen un sprung components start to
resonate with sprung components.resonate with sprung components.
PitchingPitching
RollingRolling
BouncingBouncing
8/3/2019 Characteristics of NVH
17/26
ShakeShake
Vibrations felt in theVibrations felt in thesteering wheel, seat,steering wheel, seat,or floor.or floor.
Two types of shakeTwo types of shakeare:are: VerticalVertical
LateralLateral
Generally has aGenerally has afrequency between 10frequency between 10to 30 Hz.to 30 Hz.
8/3/2019 Characteristics of NVH
18/26
Vertical Shake;Vertical Shake; a severe vertical vibrationa severe vertical vibration
of the seat, body, or steering wheel. Aof the seat, body, or steering wheel. A
trembling engine hood or rear view mirrortrembling engine hood or rear view mirror
may also be a symptom.may also be a symptom.
Lateral ShakeLateral Shake; a severe side to side; a severe side to side
vibration of the seats, body, or steeringvibration of the seats, body, or steering
wheel. The shake of the drivers waist maywheel. The shake of the drivers waist may
also be a symptom.also be a symptom.
8/3/2019 Characteristics of NVH
19/26
Possible Causes of a ShakePossible Causes of a Shake
Roughness of the roadRoughness of the road
Tire imbalanceTire imbalance
NonNon--uniform tiresuniform tires Bent or out or roundness of wheelsBent or out or roundness of wheels
DrivelineDriveline
EngineEngine
8/3/2019 Characteristics of NVH
20/26
ShimmyShimmy
Vibration that causes the steering wheel toVibration that causes the steering wheel to
oscillate.oscillate.
Typically has a frequ
ency between 5 andTypically has a freq
uency between 5 an
d15 Hz.15 Hz.
The two main types of shimmy are:The two main types of shimmy are:
Low speed shimmyLow speed shimmy
High speed shimmyHigh speed shimmy
8/3/2019 Characteristics of NVH
21/26
Low speed shimmyLow speed shimmy; when the steering; when the steering
wheel begins to vibrate when driving overwheel begins to vibrate when driving over
a bump at low speeds. (Bump Steer)a bump at low speeds. (Bump Steer)
High speed shimmyHigh speed shimmy; when the steering; when the steering
wheel vibrates on smooth roads atwheel vibrates on smooth roads at
highway speeds.highway speeds.
Typically occurs within a limited speed range.Typically occurs within a limited speed range.
8/3/2019 Characteristics of NVH
22/26
Main Causes of a ShimmyMain Causes of a Shimmy
Roughness of roadRoughness of road
Tire ImbalanceTire Imbalance
NonNon--uniform tiresuniform tires
Bent or out ofBent or out of
roundness of theroundness of the
wheelwheel
8/3/2019 Characteristics of NVH
23/26
Brake ShudderBrake Shudder
Causes the instrument panel, steeringCauses the instrument panel, steering
wheel, and sometimes the entire body towheel, and sometimes the entire body to
vibrate vertically and back and forth.vibrate vertically and back and forth.
Peaks at 40 to 50 mph and has aPeaks at 40 to 50 mph and has a
frequency of 5 to 30 Hz.frequency of 5 to 30 Hz.
The major sources of shudder are:The major sources of shudder are:
Brake rotor run outBrake rotor run out
NonNon--uniform thicknessuniform thickness
8/3/2019 Characteristics of NVH
24/26
Certain operating conditions can greatlyCertain operating conditions can greatly
affect these vibrations:affect these vibrations:
Extended periods where the vehicle is not inExtended periods where the vehicle is not in
operation.operation.
Brake disc surface irregularities caused byBrake disc surface irregularities caused by
foreign substances (saltwater, antifreeze, etc)foreign substances (saltwater, antifreeze, etc)
Deformation of brake drum cause by poorDeformation of brake drum cause by poorinstallation.installation.
8/3/2019 Characteristics of NVH
25/26
HarshnessHarshness
Many customers use the word harshnessMany customers use the word harshness
to describe ride comfort concerns.to describe ride comfort concerns.
Occ
urs when a vehicle vibrates when
Occ
urs when a vehicle vibrates whenmoving across road joints, projections,moving across road joints, projections,
depressions or stepped paved roaddepressions or stepped paved road
surfaces.surfaces.
Typically has a vibration of 30 to 60 Hz.Typically has a vibration of 30 to 60 Hz.
8/3/2019 Characteristics of NVH
26/26
The level of theThe level of the
vibration or harshnessvibration or harshness
changes withchanges with
suspension andsuspension andbushing design andbushing design and
type.type.
Top Related