nvh analysis in automobiles
TRANSCRIPT
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 and controlled..
HARSHNESS
• 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
WHAT IS NVH
• 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.
NVH 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
NVH 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 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 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%
Instruments Needed• Sensors
* microphone * hydrophones * accelerometers
• Data Acquisition Devices* analog-to-digital converters (ADCs), * anti-aliasing filters * signal conditioning
ACOUSTICS • Acoustics 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 ακουστικός (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.
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 HzNoise - 25Hz - 20KHz
• 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