nvh analysis in automobiles

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NVH ANALYSIS IN AUTOMOBILES

NOISENoise is a audible sound generated in vehicle or any other system including engine, driveline, tire contact patch and road surface, brakes, clutches, gearbox , cooling fan etc. It can be measured

VIBRATIONSThey are very low frequency energy propagations thro a medium They are produced in the driveline and The medium of vibration can be any part of a vehicle. They can be measured and controlled. .

HARSHNESSHarshness is a combination of NOISE and VIBRATIONS which creates an uncomfortable feeling in occupants of that vehicle. They just can be felt and can be JURY evaluated

WHAT IS NVHNoise, vibration, and harshness (NVH), also known as noise and vibration (N&V), is the study and modification of the noise and vibration characteristics of vehicles, particularly cars and trucks.

NVH TypesInterior NVH deals with noise and vibration experienced by the occupants of the cabin, while Exterior NVH is largely concerned with the noise radiated by the vehicle, and includes drive-by noise testing

NVH SOURCESThey including the engine, driveline, tire contact patch and road surface, brakes, wind. Noise from cooling fans, alternator, and other engine accessories is also fairly common

Why NVH is necessary?Noise Pollution CMVR, CPCB & NCNPC Customer Awareness Of Vehicle Ride Comfort Marketability Trend Towards Higher Power And Smaller Size Power trains. Sound Quality Design Optimization Consistency In Production

NVH ClassificationBy Noise Type By Vehicle Systems Vehicle Components

By NOISE TypeRoad NVH Wind Noise Powertrain/Driveline NVH Squeak /Rattle

By VEHICLE Systems

Body NVH Chassis NVH

By VEHICLE ComponentsClimate Control System Wipers Seat Motors Switches

NVH AnalysisNoise contributions from various systems #Fan and Radiator Assembly 10% # Drive Line 14% # Engine -21% # Intake System-14% # Exhaust System 32% # Structural Components- 10% # Miscelleneous-3%

Automotive Noise Sources-Levels and Frequency Bands

Noise Sources-Levels

Actual Testing Of PASS BY NOISE of a VEHICLE

Instruments NeededSensors * microphone * hydrophones * accelerometers Data Acquisition Devices * analog-to-digital converters (ADCs), * anti-aliasing filters * signal conditioning

ACOUSTICSAcoustics is the interdisciplinary science that deals with the study of sound, ultrasound and infrasound (all mechanical waves in gases, liquids, and solids). The word "acoustic" is derived from the Greek word (akoustikos), meaning "of or for hearing, ready to hear"

Solutions For Improving Noisereducing the source strength, as in making a noise source quieter with a muffler, or improving the balance of a rotating mechanism; interrupting the noise or vibration path, with barriers absorption of the noise or vibration energy, as for example with foam noise absorbers

VIBRATIONSVibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.

Types of vibrationFree vibration Forced vibration

Vibration testingVibration testing is accomplished by introducing a forcing function into a structure, usually with some type of shaker

Vibration IsolationVibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations #Passive isolation #Active isolation #Subframe isolation

Vehicle Ride ComfortRide comfort in a vehicle is a subjective perception normally Associated with level of comfort experienced during traveling in a vehicle. Perceived ride is cumulative effect of many factors In the vibration spectrum, Ride - 0 -25 Hz Noise - 25Hz - 20KHz Ride is a tactile and visual vibrations.

ApplicationsNVH test equipment are used for various applications such as: Engine noise vibration testing Acoustic performance testing Sound power testing Pass by noise testing Telephone testing Environmental noise measurements and noise field mapping Structural dynamics and vibration testing Occupational health and safety

ADVANTAGESMost comfortable ride Least fatigue More workability of the occupants

Some common examples where NVH Analysis is applied.VOLVO Busses & Trucks

Mahindra SCORPIO

Tata SAFARI

Conclusions The need to improve product quality and differentiate from the competition, concerns about human health and safety combined with stringent regulations, create a viable market for NVH.