Jun 02

Pitch – The physical quality of sound that relates to the frequency of the wave.

01-pitch-belt squeaking creates high frequency high pitched noise-roller bearing makes low frequency low pitched noise

Radial Force Variation (RFV) – A measurement of the tire’s uniformity, under load, in regards to the variation of the load acting towards the center of the tire; commonly referred to as the tire’s sidewall variation.

01-lateral run out-number of disturbances-vibration order

Radial Run out – A condition where a rotating component does not rotate in a true plane. The component moves up and down on its rotational axis.

Resonance – The tendency of a system to respond increasingly to a compelling force oscillating at, or near, the natural frequency of the system. This causes a sudden and large vibration.

01-vibaration-compelling force-beat-bead seating-reliability analysis-durability analysis

Road Noise – A noise that occurs while driving on gravel or roughly paved roads at all vehicle speeds, or when a vehicle is coasting.

01-harshness-nvh harshness-lack of suspension feel

Shake, Lateral – A side-to-side vibration of the body, seats, and steering wheel.

Shake, Vertical – An up and down vibration of the body, seats, and steering wheel.

01-Vehicle Shake-Steering wheel shake-vibration in steering wheel-vertical shake-lateral shake

Shimmy, High-Speed – A vibration that causes the steering wheel to oscillate when driving on smooth roads at high speeds.

Shimmy, Low-Speed – A vibration that causes the steering wheel to oscillate when driving across a bump at low speeds.

01-shimmy-steering wheel to oscillate-high speed shimmy-low speed shimmy-due to roughness of road-tire imbalance

Source Component – The component that is diagnosed as being the root cause of a vibration or noise concern.

Sound – The result of a vibrating disturbance of an object, which produces waves that transmit out from the source.

01-noise-nvh noise-types of noise-car noise-unexpected sound

Static Balance – The method of balancing a tire and wheel assembly in a single plane. Static balancing removes only the lateral (side to side, wobble) imbalance and the tire and wheel assembly could possibly have a radial (up and down) vibration.

Torque Sensitive Vibration or Noise – A vibration or noise that is sensitive to different loads and torque, applied to the drive train of a vehicle. The vibration or noise changes when the throttle position or transmission gearing is used, during a road test, to change the torque applied to the drive train.

Vibration – The repetitive motion of an object, back and forth or up and down, which may be felt or heard.

01-automotive-NVH-brakeSqueal-vehicle NVH-brake squeal analysis-finite element analysis-vibration force-shudder

Wheel Diameter – The dimension of a wheel measured on the inside of the wheel at the bead seat area.

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May 31

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

01-audible range of sound-pitch-intensity-sound-soundwaves-NVH noise-level

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

01-amplitude-sound-cycle

01-vibration amplitude-sound waves-vibration level

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.

01-vibaration-compelling force-beat-bead seating-reliability analysis-durability analysis

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.

01-damping system-dampers-suspension system-dampen noise-dampen vibration-dynamic balance

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).

01-droning-non directional noise-low pitched noise

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.

01-harshness-nvh harshness-lack of suspension feel

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.

01-intensity-direction flow-acoustic energy

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.

01-lateral run out-number of disturbances-vibration order

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.

01-magnitude-amplitude-resonant-resonance frequency-intensity of vibration

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.

01-noise-nvh noise-types of noise-car noise-unexpected sound

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).

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