Noise Vibration Harshness

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NVH component in the car on the front wall as acoustic insulation of the interior

Noise, vibration, harshness ( NVH , "noise, vibration, roughness") collectively describes the audible or perceptible vibrations in motor vehicles or machines. Roughness refers to the audible as well as tactile transition range in the range from 20 Hz to 100 Hz. In general, the cause of NVH is the local application of force from a vibration source in vibration-transmitting media (such as mechanical structures in motor vehicles). Specifically, the reasons for vibrations are mostly stick-slip effects (self-excited frictional vibrations) in the vehicle, which are either side effects of intentional friction or arise unintentionally from solid body friction and lead to the emission of structure-borne noise and ultimately audible air- borne noise . Typical examples of NVH are squeaky brakes , rattling wiper, transmission howl, plucking of the clutch , or noises of the vehicle air conditioning. Another reason for the development of vibrations is the excitation of component natural frequencies .

In practice, such effects are assessed by the automobile manufacturers and their suppliers in order to assess the risk of complaints and to ensure the acceptance of the product by the vast majority of customers. The evaluation is made, for example, depending on these factors:

  • Driving situation: If the noises only occur when the driver is in a stressful situation, he perceives the corresponding noises less.
  • The driver's expectations: squeaking brakes, rattling windshield wipers and braking noises generated during ABS activity are more likely to be accepted than noises in the ventilation. Certain driving noises are accepted by sports car drivers, while limousine drivers claim the same noises.
  • Sensitivity of the customer group: empirical values ​​about when the majority of customers notice NVH at all and when the tolerance threshold for complaints is exceeded.

A distinction must be made between measures against NVH and the acoustic design of engine and exhaust noises, slamming doors or active electric motors. NVH is about avoiding vibrations that impair driving comfort, while acoustic design is about optimizing expected audible noises in terms of the buyer's ideas and associations.

literature

  • Helmut Tschöke: The electrification of the drive train: basic knowledge. Springer-Verlag 2014, ISBN 3-658-0464-49 , p. 165.

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