NVH | Noise Vibration And Harshness | NVH Basics | NVH Analysis | Noise Vibration And Harshness Introduction

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NVH stands for noise, vibration, and harshness.

Noise is unwanted sound; vibration is the oscillation that is typically felt rather than heard. Harshness is generally used to describe the severity and discomfort associated with unwanted sound and/or vibration, especially from short duration events.

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The automotive industry is currently spending millions of dollars on NVH work to develop new materials and damping techniques. The new design methods are starting to consider NVH issues throughout the whole design process. This involves integrating extensive modeling, simulation, evaluation, and optimization techniques into the design process to insure both noise and vibration comfort.  New materials and techniques are also being developed so that the damping treatments are lighter, cheaper, and more effective.

Some of the methods used to control noise, vibration, and harshness include the use of different carpeting treatments, the addition of rubber or asphalt material to car panels, gap sealant, and the injection of expandable foam into body panels.  The carpeting treatments include varying types of foam padding combined with different weights of rubber-backed carpet. 

The overall result of this technique is a mass-spring system that acts as a vibration absorber.  The rubber or asphalt materials are attached to various car panels to add damping and mass loading to reduce vibration levels and the rattling sounds from the panels.   Sealant is applied to close gaps in order to increase the transmission loss from the engine, wind, and road noise sources to the vehicle interior.  Expandable foam injected between panels, such as the dashboard and firewall, helps to add stiffness and vibration absorption.

All of these current methods are effective at reducing sound and vibration levels in a vehicle at higher frequencies.  However, some of the treatments become almost ineffective at lower frequencies below 200 Hz.  The treatments also add a substantial amount of weight to the vehicle, thus affecting its fuel economy, as well as adding cost.

NVH Test Equipment’s:

  • Analyzers,
  • Shakers and controllers,
  • Accelerometers,
  • Noise dosimeters,
  • Octave band filters,
  • Transducers for vibration and acoustics,
  • Dynamometers,
  • Sound level meters,
  • Microphones, and
  • Analysis software (Ricardo, Altair NVH Director, LMS Virtual Lab etc.)

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Recent NVH Test Equipment’s:

  • PC based analyzers,
  • Multichannel NVH data acquisition systems,
  • Acoustic holography devices,
  • Laser vibrometer’s, and
  • Anechoic test cells.

NVH Applications:

  • Engine noise vibration testing
  • Acoustic performance testing
  • Sound power testing
  • Pass by noise testing
  • Telephone testing
  • Environmental noise measurements and noise field mapping
  • Structural dynamics and vibration testing
  • Occupational health and safety

Advantages of NVH Test Equipment:

2010 Buick LaCrosse CXS HiPer Strut Front Suspension

  • Real-time multi-analysis is possible in one test run
  • Results obtained are accurate and precise
  • Report generation is made easy
  • Shorter lead times, and hence improved productivity
  • Thermoforming Materials | Vacuum Forming Materials | Pressure Forming Materials

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    Material & Description

    ABS

    Good general purpose material, very tough yet very hard and rigid, good impact and electrical. Available in gauges from .040 to .475 with several extruded textures. Comes opaque and can be matched in custom colors.

    ABS/PC

    A blend or alloy of ABS and polycarbonate that thermoforms well, weathers well, good color retention, very hard, excellent impact.

    ABS/PVC

    Flame retardant, tough.

    Acrylic

    Outstanding weather resistance, excellent optics and electrical properties, poor impact, high gloss and deep luster. Available in standard gauges from .080 to over 1". Available in clear, transparent and opaque colors.

    Acrylic, cell cast

    Excellent optics and hot strength, more expensive. Acrylic, continuous and extrusion cast.
    Large volume use and best price, good optics.

    Acrylic film

    3 or 6 mil film for laminating, decorating, and weathering of extruded ABS.

    DR Acrylic

    Modified acrylic with higher impact properties.

    Acrylic/PVC

    A blend of acrylic and PVC that is a tough, chemical-resistant material that weathers well and is flame resistant. Available in custom colors.

    HDPE (high-density polyethylene)

    Crystalline, very tough materials, good weather resistance with UV inhibitors, resistant to many chemicals. Available in standard gauges from .040 to .500. Available in opaque custom colors. Tough and stiff. Good low temperature. Economical.

    HMWPE (high molecular weight)

    Excellent environmental stress crack properties, thermoforms well, good low temperature.

    HIPS (high impact polystyrene)

    Good general-purpose material, rigid. Available in clear but usually opaque custom colors from .030 to .350, low cost.

    PVC (vinyl)

    Good general-purpose material, good abrasion and chemical resistance. Available in clear but usually opaque custom colors from .030 to .125.

    Expanded PVC

    Stiff, light, flat, thermoformable. Available in stock colors and gauges, generally 3 and 6 mm but others also available.

    PETG

    Clear, higher impact than acrylic, easy to form. Available in gauges from .030 to .500.