NVH or Noise Vibration Harshness

What is NVH?

NVH, or noise vibration harshness, is also called just noise and vibration. N&V is the study and modification of vibration and noise characteristics of cars and trucks. Even though vibration and noise may be measured easily, harshness is at a certain level subjective, and it is measured using jury evaluation or analytical tools that may offer the results that reflect the human subjective impression. These are tools that belong to the field of psychoacoustics.  Interior NVH will deal with vibration and noise that are being experienced by the occupants of a cabin, and exterior NVH measures the noise which is being radiated by a vehicle, and this includes the testing of drive-by-noise.

Why is NVH testing necessary?

NVH is at a certain level about engineering, but the objective measurement may fail to correlate and predict well with the impression of a human observer. Even if the response of the human ear to moderate noise is around A-Weighting, there are two different types of noise that have an A-level, and they are not always disturbing at an equal level.  A field called psychoacoustics is mostly concerned with such a correlation. There are cases where an NVH engineer may be asked to change the sound quality while subtracting or adding some harmonics but not making the car quiet.

Applications of NVH

The HEAD acoustic offers a harmonized solution in many different applications and fields.  The following are some examples of applications where it is being used.

  • Conducting a listening test: this is about conducting and planning of listening tests. Demonstrating how this works requires listening NVH software.
  • Binaural measurements, playback, and analysis: this is about the benefits of equalization and application interface while taking into account the playback equalization.
  • Psychoacoustic analysis: this describes the correlation of sensation of a human to the sound compared to the parameters of its physical sound. This means that pure physical parameters like the degree of modulation, duration, bandwidth, frequency and level will be depicted against the psychoacoustic parameters or accurate parameters.
  • Detection of a sound pattern: human hearing is sensitive to temporal changes in the acoustical signals with spectral structures that have distinct minima and maxima. It implies that human hearing is used to assess the sound pattern. With the analysis of relative approach using analysis software, the sound patterns may be visualized.

Vehicle NVH

The best NVH service has become a vital part of car development since it targets product quality, customer satisfaction, and driving pleasure. There are advanced virtual and experimental tools that are needed to ensure timely and cost-effective development while minimizing the issues that occur in pre-production and shortening how long it takes for the car to go to market.  The scope of using NVH starts from its benchmark while it targets settings, low noise powertrain, sound design, and driveline development with NVH engineering in the integration of the vehicle.  NVH is not used only for the passenger cars but also for the industrial and off-road machinery and trucks.

The NVH for a car includes:

  • Components induced NVH
  • Rattle and Squeak
  • Sound quality and sound design
  • Legal
  • Sound package
  • Road NVH
  • Power trains induced NVH
  • Aeroacoustics
  • Body acoustics
  • Transmission and engine NVH

How is quality NVH achieved?

To achieve the best NVH development, it is important to take into account the strength of the FEV since there is a need to understand the vehicle and the power train. A reliable and successful NVH development should be based on a deep knowledge of noise sources and the corresponding transfer paths that have been proven with different projects throughout the entire world. The challenge for the NVH specialists is to support the design and concept through the development process with reliable recommendations before the design freeze and concept.  The car specialists have in-house methodologies that they use to do NVH optimization and simulation.

Meaning of NVH test

NVH is the term that is used for noise, vibration, and harshness. The NVH test is used to search for the source of a vibration, shake or noise.  It is used for the entire range of where there is a perception of vibration, feeling or hearing. The noise is normally an unwanted sound while the vibration is oscillation that is felt but not heard. Harshness is meant to describe the discomfort and severity that is associated with unwanted vibration and sound, mostly from a short duration event.

When is an NVH test required

NVH is also called sound quality analysis, and it is meant to measure the exposure NVH level, NVH noise, sharpness, and loudness.  Because of too much noise coming from communication activities, transportation, and frenetic manufacturing, the NVH control and NVH reduction have become a concern of everyone involved.  It affects a car’s safety, the construction of a building, and the level of noise at work and home.

 

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