Definition of Noise, Vibration, and Harshness

Noise is any unwanted sound, usually unpleasant in nature. Possible sources of noise are:
- the engine.
- the engine accessories.
- the intake and exhaust systems.
- the driveline.
- electric motors and pumps.
- the wind.
- mechanical pumps.
- the road surface.

Vibration is an unwanted periodic motion of a body or medium. It may be felt, heard, or seen. Possible sources of vibration include the:
- tires.
- engine.
- engine accessories.
- suspension.
- driveline.
- exhaust system.

Harshness refers to the ride quality and is very subjective. Reference to the previous conditions is usually the only way to identify harshness as a symptom.