Nvh Terms | Nvh Terminology -1

Audible Range of Sound – Sounds that are in the range of 20 to 20,000 Hertz (Hz).

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Amplitude – The vertical measurement between the top and bottom of a wave. Also see magnitude.

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Beat – An NVH concern produced by two sounds that is most noticeable when the frequency difference is 1 to 6 Hz.

Bead Seating – The process of seating the tire to the rim. If properly lubricated the bead seating occurs when the tire and wheel are assembled.

Compelling Force – A vibrating object acting upon another object that causes the other object to vibrate.

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Cycle – The path a wave travels before the wave begins to repeat the path again.

Dampen – To reduce the magnitude of a noise or vibration.

Dampers – A component used to dampen a noise or vibration. Foam and rubber are commonly used to dampen vibrations.

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Dynamic Balance – A procedure that balances a tire and wheel assembly in two planes. Dynamic balance removes radial and lateral vibrations.

Droning, High-Speed – A long duration, non-directional humming noise that is uncomfortable to the ears and has a range of 50 mph (80.5 kph) and up.

Droning, Low-Speed – A long duration, low-pitched noise that is non-directional and has a range of up to 30 mph (48 kph).

Droning, Middle-Speed – A long duration, low-pitched noise that is non-directional and has a range of 30 to 50 mph (48 to 80.5 kph).

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Electronic Vibration Analyzer – An electronic NVH diagnostic tool that measures frequency and amplitude.

Frequency – The number of complete cycles that occurs in a given period of time.

Harshness – An aggressive suspension feel or lack of give in response to a single input.

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Hertz – The unit of frequency measurement in seconds (a vibration occurring 8 times per second would be an 8 Hz vibration).

Intensity – The physical quality of sound that relates to the amount and direction of the flow of acoustic energy at a given speed.

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Lateral Run out – A condition where a rotating component does not rotate in a true plane. The component moves side-to-side (wobbles) on its rotational axis.

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Magnitude (Amplitude) – The amount of force or the intensity of the vibration. The magnitude or strength of a vibration is always greatest at the point of resonance.

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Medium – Provides a path for sound waves to travel through.             

Natural Frequency – The frequency that a component will vibrate the easiest. Normally, the larger the mass, the lower its natural frequency.

●       Engine block (2-4 Hz)

●       Tire and wheel assemblies (1-15 Hz) – proportional to vehicle speed

●       Suspension (10-15 Hz

●       Driveline (20-60 Hz)

●       Differential components (120-300 Hz)

Noise – The unpleasant or unexpected sound created by a vibrating object.

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Order – The number of disturbances created in one revolution of a component.

Phase – The position of a vibration cycle relative to another vibration cycle in the same hertz rate (time frame).