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New technologies in sound dampening

Friday, March 1, 2019 - 08:00
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During vehicle teardown, the technician should closely examine (to determine softness and stiffness) and identify what is currently installed by both looking and touching the material that needs to be replaced. This will help ensure that the repairer is able to choose the proper NVH material or replicate it as closely as possible.

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Some parts and materials – such as fiberglass-reinforced epoxy patches that adhere to the inside of fenders, doors and quarter panels and are cured when the vehicle undergoes an OEM’s e-coat and curing processes – are intended to provide extra support to exterior body panels in areas that may be prone to oil canning or panels that manufacturers have identified as commonly leaned against where the load needs to be spread out. (Yes, OEMs do actually consider the user’s actions, such as leaning against a vehicle, and try to provide some protection/additional support.)

These types of patches are often, but not always, included with service parts. When they are not included, additional effort is needed to complete the repair, but some patches can be fully recreated in the field. Repairers can remove the original patch and re-adhere it with adhesive as one option. Other options include the following:

  • Using sprayable sound dampeners (Fusor HD, for example) or self-adhering products applied to the inside of the panel in question. The technician needs to determine what will be proper if the OEM guidelines do not make it clear. Replace a stiff patch with something stiff and a flexible patch with similar pliability.
  • Replacing the coatings – both inside and out – on the underbody. This is very important as it will eliminate the pinging sound created if, for example, a stone flies up and hits the floor. A minor noise heard inside the vehicle from a stone outside of it may not seem like a big deal. However, eliminating that kind of sound is more than simple noise reduction. The ping created from that same stone hitting the underbody could be picked up by various sensors and misconstrued as an issue.

For example, it could affect the vehicle’s yaw sensor. When the floor above the transmission panel in a vehicle by one particular manufacturer gets hit by a stone, it triggers a body sensor. A miscommunicated data point from that sensor, along with all the other data from other sensors, can cause the malfunction indicator lamp (MIL) lamp to illuminate as “confusion” exists. To address the situation, the OEM has issued a bulletin with its recommended NVH materials to use during vehicle repair so the “sound” is dampened should a stone bounce around and hit the underbody in the area of concern.

Beyond noise reduction

New technologies in sound dampening allow some materials to be applied directly to bare metal. Direct-to-metal (DTM) technology resists surface corrosion while providing a sound-deadening solution.

In addition to the sound control NVH materials offer, they also provide excellent corrosion protection. New technologies in sound dampening allow some materials to be applied directly to bare metal. Direct-to-metal (DTM) applications include floor plans, strut towers, core supports, core supports, trunk area, inner wheel wells, aprons, and door hem flanges.

This means the body shop doesn’t have to purchase substrate primer and the repairer doesn’t have to spend time applying it, which improves cycle time and reduces costs. Spray application of seam sealer can be applied as a surface coating to large areas of a vehicle as a durable treatment to provide customers with a robust solution.

Use of DTM technology resists stone impingement-causing surface corrosion and also provides a sound deadening solution. It is a “win-win” for both the customer and the autobody shop.

Although some repair facilities still shy away from using DTM (and some may never accept it as a solution), this sound dampening technology is continuing to grow. Products have been tested and approved for performance, giving shops confidence and making them more comfortable in using DTM when applying sound dampening materials.

Advantages and applications of the direct-to-metal process
  • Elimination of substrate primer: This improves cycle time and reduces costs.
  • High performance: Provides excellent adhesion to bare or primed surfaces.
  • Easy to finish: Can be tooled, wiped clean, sanded and/or painted immediately.
  • Excellent corrosion protection: Meets J2334 cyclical corrosion for the vehicle lifetime.
  • Versatile: Bonds to epoxy or urethane-primed surfaces. Can use one-component (direct to metal or HD) two-component sealers (example: Fusor 019 bare metal brushable acrylic seam sealer), and it encapsulates the weld with minimal burn back.
  • Appearance: Easily duplicates factory appearance and provides a flexible seal without shrinkage, cracking or sagging.
  • Bare metal applications: Floor pans, strut towers, core supports, trunk area, inner wheel wells, aprons, door hem flanges.

Next-gen and luxury vehicle opportunities

Electric vehicles (EVs) and hybrid electric vehicles (HEVs) offer many benefits, but they also come with their own NVH challenges. Noise from high-frequency electric motor generators and power control unit high-frequency switching, engine startup and stop noise and vibration, and the “whine” sound from power-split system gears and battery cooling all create undesired acoustical issues.

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