New technologies in sound dampening

March 1, 2019
With comfort as a top priority for vehicle owners, here’s how shops can take advantage of upgrade opportunities in noise reduction.

As demand for passenger vehicles continues to expand in emerging markets and they become more technologically advanced, consumers are placing greater importance on maximizing comfort and creating the best overall driving experience.

Noises created from a vehicle’s structure as well as airborne noises may cause passenger discomfort or annoyance. However, new technologies and advances in noise, vibration and harshness (NVH) materials for sound dampening are providing options to eliminate extra noise from in-cabin vibrations and friction.

NVH materials – acoustic devices generally classified as sound-absorbing materials, sound-barrier materials, and sound dampening materials – are used both inside and outside a vehicle to eliminate noise. Liquid applied spray dampers, liquid applied sound dampers, liquid applied sound deadener, and liquid applied spray deadener are all different terminologies for NVH materials used for the same process – applying a layer of material to dampen sound transmission.

Technicians use automotive noise, vibration and harshness (NVH) materials in repairs to provide either acoustic absorption or acoustic insulation to absorb sound.

Creating a heavy layer – the thicker the layer, the less sound that can come through – will diminish or eliminate noise. These materials, however, are not only used during the collision repair process, but some vehicle owners are also requesting additional sound dampening following the installation of aftermarket accessories and systems, such as an upgraded stereo.

Understanding post-repair sound dampening

With the global automotive NVH market expected to grow more than 10 percent through 2021 for several reasons – such as more vehicles with active noise control systems, consumer preferences about comfort and safety, and even changing regulatory frameworks – it is important for repair technicians to understand what aftermarket sound dampening materials are available and how to use them.

One of the biggest consumer complaints about a vehicle post repair is that sounds “tinny” – like a tin can or an irritating, high-pitched noise – from inside. More often than not, technicians repair the fender or door but haven’t replaced NVH or beta patches or have not reattached door skins to the body structure – such as underneath a door beam.

This all affects sound dampening. Eliminating – or at least reducing – any noise or vibration does not change just how a car rides but how it actually feels. Automotive NVH materials provide either acoustic absorption or acoustic insulation to absorb sound. Noises and audible body sounds are two of the biggest problems/complaints from vehicle owners, which contribute to how a vehicle handles and to the overall driver experience.

A tinny sound comes from not replacing NVH material removed during vehicle repair. It is absolutely critical to put back any sound dampening material originally installed by the OEM during the assembly process.

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.

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.

To that end, higher-end and luxury vehicle customers often have certain expectations for sound quality within specific automobiles. Tailoring vehicle acoustics to meet OEM preferences or to set the manufacturer apart from competitors is becoming more commonplace.

The driver or passenger in a luxury vehicle often has certain expectations about its acoustics. He or she may anticipate nearly full isolation from any airborne or structural vibration noise. If a customer returns a vehicle to the body shop because it “just doesn’t sound right,” a technician now has to re-evaluate the repair.

Regardless of whether the vehicle comeback is because of noise from an improper or incomplete repair of NVH material or due to structural noise or vibration, it can still affect customer perception. Autobody shops need to be proactive and prevent any negative thoughts about the repair job or facility, which influences the overall customer experience. This in turn may have an effect on Customer Service Index (CSI) scores, one of the key performance indicators (KPI) essential to a collision repair shop’s success.

Shop management and technicians should consider using this as an opportunity. Collision repair facilities could suggest using a sprayable seam sealer in the wheel wells or underbody– even if the vehicle OEM did not originally put NVH materials in these areas – because it will reduce noise inside the vehicle. Using a DTM product with sound dampening in these locations also will provide better corrosion protection.

These are opportunities to upsell to a customer, which can create revenue for the shop and help ensure customer satisfaction. The customer may not be able to differentiate inherent structural noise from a vehicle (that was there before the repair was done but just not previously noticed) and noise or vibrations from not properly replacing NVH materials.

Regardless, it may make for a dissatisfied customer. Shop management can help prevent customer complaints through upselling to improve sound dampening above and beyond proper vehicle repairs. Note that shops should provide full disclosure with any upsells – it is being offered to provide the best experience for the consumer – but is not necessary for proper vehicle repair.

NVH restoration materials, along with all other “non-liquid” supplies, need to be included on the estimate/blueprint for cost recovery when required. Insurers, or the customer if a self-pay cash job, will pay for those products necessary for completing a repair when they are itemized and have a logical explanation.

Boosting your business with satisfaction

Ultimately, the goal for any repair job is to structurally and aesthetically restore a damaged vehicle to its pre-accident condition by fulfilling both OEM guidelines and safety requirements – and having a satisfied customer. 

Although a properly repaired vehicle technically should result in customer satisfaction, it’s not always the case. Autobody shops should embrace this as an opportunity. By providing the latest in sound dampening technology options, shops can help work toward complete customer satisfaction while helping out their own businesses.

For tips on how to confidently choose and use seam sealers and foams to reduce noise, vibration and harshness during vehicle repair, see “The Art and Craft of Repairing With Seam Sealers and Foams” in the November 2018 issue of ABRN.

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