Definition of Noise, Vibration, and Harshness

Noise is any unwanted sound, usually unpleasant in nature. Possible sources of noise are:
- Engine.
- Intake and exhaust system.
- Driveline.
- Wind.
- Road surface.

Vibration is unwanted medium to high frequency movement that is either regular or random in nature. It may be felt or heard. Possible sources of vibration are:
- Tires.
- Engine.
- Engine accessories.
- Suspension.
- Driveline.

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.