´NVH ANALYSIS IN AUTOMOBILESµ
NOISE Noise 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
NOISE Noise 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
VIBRATIONS
They 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 me asured and controlled..
H ARSHNESS
Harshness
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 ³
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WH AT
IS N VH
Noise, 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.
N VH Types Interior 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
N VH SOURCES They 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
N VH is necessary?
Noise Pollution ± CM VR, 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
N VH Classification By Noise Type By Vehicle Systems Vehicle Com ponents
By NOISE Type
Road
NVH
Wind Noise Powertrain/Driveline NVH Squeak /Rattle
By VEHICLE Systems
Body NVH Chassis NVH
By VEHICLE Components Climate Control System Wipers Seat Motors Switches
N VH Analysis Noise 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 P ASS BY NOISE of a VEHICLE
Instruments Needed Sensors * microphone * hydrophones * accelerometers Data Acquisition Devices * analog-to-digital converters (ADCs), * anti-aliasing filters * signal conditioning
ACOUSTICS
is the interdisciplinary science that deals with the study of sound, ultrasound and infrasound (all mechanical waves in gases, liquids, and solids). Acoustics
The word "acoustic" is derived from the Greek word (akoustikos), meaning "of or for hearing, ready to hear"
Solutions For Improving Noise reducing 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
VIBRATIONS Vibration 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 vibration Free vibration Forced vibration
Vibration
testing
Vibration
testing is accomplished by introducing a forcing function into a structure, usually with some type of shaker
Vibration
Isolation
Vibration 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 Comfort
Ride 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 - 20K Hz Ride is a tactile and visual vibrations.
Applications NVH 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
AD V ANTAGES Most comfortable ride Least fatigue More workability of the occupants
Some common examples where N VH Analysis is applied.
VOL VO
Busses & Trucks
Mahindra SCORPIO
Tata SAFARI
