Definition of Noise, Vibration, and Harshness

Noise is any unwanted sound, usually unpleasant in nature. It may be regular and/or random in nature. Possible sources of noise are the:
- Engine.
- Engine accessories.
- Intake and exhaust system.
- Driveline.
- Electric motors/pumps.
- Wind.
- Mechanical pumps.
- Road surface.

Vibration is unwanted, tactile feel, which may be either steady or random in nature. It may be felt or heard. Possible sources of vibration include:
- Tires.
- Engine.
- Engine accessories.
- Suspension.
- Driveline.
- Exhaust system.

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