Definition of Noise, Vibration, and Harshness

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

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.