Definition of Noise, Vibration, and Harshness

DEFINITIONS

Noise is any Unwanted Sound, Usually Unpleasant in Nature. Possible Sources of Noise are the:
- engine.
- intake and exhaust system.
- driveline.
- wind.
- road surface.

Vibration is Unwanted, Low- to Medium-Frequency Movement Which may be 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 Subjective. Reference to Previous Conditions is Usually the Only Way to Identify Harshness as a Symptom.

DIAGNOSTIC THEORY

The Shortest Route to an Accurate Diagnosis Results from:
- system knowledge, including comparison with a known good system.
- system history, including repair history and usage patterns.
- condition history, especially any relationship to repairs or sudden change.
- knowledge of probable causes.
- using a systematic diagnostic method that divides the system into related areas.

The Diagnosis and Correction of Noise, Vibration and Harshness Concerns Requires:
- a road test to determine the exact nature of the problem.
- an analysis of possible causes.
- testing to localize the cause.
- correcting any problems found.
- a road test to make sure the problem has been corrected.