Nvh Analysis in Automobiles

“NVH ANALYSIS IN AUTOMOBILES”

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 Classification

• By Noise Type

• By Vehicle Systems • Vehicle Components

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

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%

Automotive Noise Sources-Levels and Frequency Bands

Noise Sources-Levels

Actual Testing Of PASS 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 • 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.

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 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

ADVANTAGES

• Most 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.