Introduction to NVH in Automobiles

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What is NVH ?

Noise, Vibration and Harshness is the study of the noise and vibration characteristics of the vehicles particularly cars and trucks.


NOISE : 
  • Noise is an audible sound generated from engine, driveline etc.
  • It can be measured.

VIBRATION :
  • They are very low frequency energy propagations through a medium.
  • Produced in the driveline, the medium can be any part of the vehicle.
  • Can be measured and controlled.
HARSHNESS : 
  • Harshness is a combination of Noise and Vibration which creates an uncomfortable feeling in the occupants.
  • They can be felt and can be "Jury" evaluated.

CLASSIFICATION OF NVH :

INTERIOR : NVH deals with noise an vibration experienced by the occupants 
                      of the cabin.

EXTERIOR : NVH deals with noise radiated by the vehicle.


Noise : Road Noise, Wind Noise, Power-train, Squeak/ Rattle etc.

Vehicle Systems : Body NVH, Chassis NVH etc

Vehicle Components : Climate Controls, Wipers etc.


NOISE CONTRIBUTIONS FROM SOURCES :
  • Fan and Radiators Assembly ---- 10%
  • Drive Lines----- 15%
  • Engine----- 20%
  • Exhaust----- 30%
  • Structural components----- 10%

CHARACTERISTICS OF VIBRATION :
  • Ride Comfort
  • Shake
  • Shimmy
  • Brake Shudder

FREQUENCY RANGE :

 Oscillatory phenomenon  Frequency (Hz)   Excitations  
  Roadway Imbalance Engine 
Ride   0-25   
Noise 25-25 KHz    
Body Vibrations 0.5-5 **   
Shake 10-30 **   
Shimmy 5-15   ** 
Brake Shudder 5-30    
Harshness 30-60 **   
Powertrain Noise 70-1000   ** 















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