Definition of Noise, Vibration, and Harshness

All vehicles produce some noise and vibration. Four-wheel drive and all-wheel drive vehicles produce different noise and vibration than front-wheel drive and rear-wheel drive vehicles. If the driver is new to a type of vehicle, he/she may think that some sounds are abnormal when they are normal for that vehicle.

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.