What are the most effective materials for reducing NVH in a car?

Automotive Noise comes from P.A.R.T.S. POWERTRAIN noise AERODYNAMIC (wind) noise ROAD noise TIRE noise SQUEAK AND RATTLE noise. Reducing the noise at the source will, generally, result in the overall lower cost countermeasure.

The best way to reduce NVH is by eliminating noise at source. Let us say there is flow separation noise from the blower motor, then make changes to blower scroll, diffuser and reduce pressure drop. This is the best way to reduce blower noise. It's a cost effective approach. Using acoustic foam help a very little .

The application of metamaterials for car NVH control offers exciting possibilities for enhancing cabin comfort and reducing noise levels. Their unique properties and ability to manipulate sound and vibration make them a promising solution for addressing NVH challenges in the automotive industry. Ongoing research and development efforts will shape the future of metamaterials in this domain, paving the way for quieter and more enjoyable driving experiences.

reduce NVH-materials like acoustic foam, mass-loaded vinyl, and sound-deadening sprays . Proper insulation and damping process set help to absorb and block unwanted noise and vibrations in vehicles or structures.

First of all act on the NVH source. Much better avoid it than isolate or absorb it, so take care of wall thickness and reinforcements of main sources. Second, depends on the nvh source. Each material is suitable for a specific need and vehicle area ( barrier, absorption, dash, floor, roof, etc....) there is not a general answer.

To reduce vibrations from engine, some of Materials used are: Natural rubber (NR), polybutadiene rubber (BR), Nitrile Rubber (NBR), epoxidized natural rubber (ENR), Neoprene (CR), Poly(Methyl Methacrylate (PMMA), polyurethane (PU), nanoclay-modified PU/polypropylene oxide-polyethylene oxide copolymer with LiClO4 20 wt% (PEL) blends system, ethylene–propylene–diene monomer (EPDM)/nylon 6 blend systems. Source : Engine mount materials from International Conference on Structural, Mechanical and Materials Engineering (ICSMME 2015)

Anecdotally (my 30+ years of experience), I have only seen the two following body panel conditions: 1) the noise coming from the panel(s) is a forced response. 2) the damping material used only shows panel mass damping (regardless of damping loss factor). This comes from on-road fully trimmed vehicle results across 25+ programs. Further note, a sound barrier affect is also shown from panel damping treatments. This led me to an Insertion Loss measurement to show any treatment's true noise attenuation performance.

Rubber is an excellent choice for use in NVH parts due to its high density, which makes it capable of easily absorbing sound and vibration while also lowering the amount of vibration that is transmitted...

Like others have mentioned foam like materials, rubberized materials, even composites that use different organic matrixes (OMCs)

NVH continues to change during the expected life cycle of a product. There are many influences that effect this. Design, the environment the product is used in, customer usage and the list goes on. Even maintenance of the product can change the NVH, tires are a perfect example of this. This being the case the focus being on materials only will give you limited results at best. A better focus may be noise cancellation in the cabin that can adapt to any change that comes from any influence whether it is a subtle, gradual or sudden.

Dampening Vibrations: Butyl Rubber and Asphalt-Based Materials Acoustic Foams for Noise Absorption: Closed-Cell and Open-Cell Varieties Mass Loaded Vinyl (MLV): A Dense Barrier Against Sound Transmission Vibration Dampeners: Pads for Targeted Impact Upgrading Engine and Transmission Mounts for Vibration Control Anti-Vibration Pads: Strategically Placed Absorption Soundproofing Sprays: Precision in Noise Reduction Interior Comfort: Carpeting and Headliner Materials for Noise Absorption Enhanced Ride Comfort: Suspension System Improvements with Bushings and Shock Absorbers Sealing and Weatherstripping: Preventing External Noise Intrusion

Based on some practice, material selection should consider about where the absorption part will be put : - We could use resinated felt for engine room, because of its moldable & rigid characteristics as finished good. - Use Thermoplastic Felt + Flame retardant material if you want to put it on the cabin.

Recently sound absorption material seems to be applied like wallpaper (maximize coverage). When you measure Insertion Loss of the "wallpaper" coverage versus little to no coverage, my results were frequently little to no overall interior noise reduction (on-road), not real cost effective. I have seen the best results with the sound absorption material directly adjacent to the source noise. And from an Insertion Loss aspect, I have seen some panel damping effect(s) when the sound absorber material is compressed onto a panel or conforms very closely to the radiating panel.

Though the fiberglass wool is a better insulation but there should be a better way to package it, enclosed. The people working with cars should be protected against its irritation.

A relatively cheap way of getting rid of resonance vibrations is by lining the inner BIW(Body in White) and closures outer panels with Dynamat type sound absorption self adhesive mats that are placed on the inside of the big flexible panels since they are the first to start vibrating due to resonant frequencies.

Here, off course we have to talk about elastomer or polyurethane bushings, engine mounts and dampers that are placed between a vibration source such as an internal combustion engine( i.e. a diesel engine) and the car structure(Body in White) or chassis, with the purpose of blocking the transmission of the generated vibrations throughout the car.

The summary of 'Benefits of reducing NVH' wraps up the whole idea but, when reducing NVH (BSR as well), the idea of robustness of the vehicle increases tremendously, even if the client faces issues like mechanical / electrical problems. It's already proven by quality surveys that clients are likely feel robustness of the product when NVH is at the bottom of the pareto.

I my opinion the biggest benefits are comfort for the passengers and most importantly the prevention of fatigue failure in certain points of the car structure and even prevention of potential fixtures loosening over time.

Given: you can't adequately objectively model and measure interior noise performance. Subjective evaluations are necessary. 100% of our customers are subjective evaluators. Anyone performing subjective evaluations should first have their hearing checked (not kidding) and second know what the customer is looking for - that is some customers are indifferent to interior noise performance (using ear buds all the time). At a minimum: directional noise (close your eyes and point to the source) and tonal noise (like hisses, pure tones and whistles) will lead to warranty. Both of these concerns normally require a subjective evaluation of some sort to root cause and develop a countermeasure.

As a matter of fact..increasing Nvh insulation results in cost and weight..but identifying and using it at the right places is key.We need to identify sustainable low cost damping materials for use in future .

Adding insulation and damping materials to reduce noise can increase the weight of the vehicle, impacting fuel efficiency and performance Developing and implementing advanced NVH solutions can be expensive, and automakers must balance the cost with the benefits, especially in the context of competitive market pressures. NVH characteristics can change under different driving conditions, making it challenging to create a solution that is effective across a wide range of scenarios. Modern vehicles often use a combination of materials, such as steel, aluminum, and composites, which can complicate NVH management due to differing acoustic properties.

Well, in my point of view, we need to consider the frequency of the BIW (naked and/or trimmed) since +80% of the client's complains, based on 7-year experience in quality survey analysis and quality reactivity processes, comes from structural and BSR noises. When we start from that, the whole development can be done w/out adding too many materials (to damp, to absorb...) that increases cost, weight... There're different contexts, indeed, but in the car industry it's pretty much the same.

NVH became particularly important with the introduction into the market of EVs In the past most of disturbing noises were covered by the intrinsical noise connected to the engine fuel combustion. Moreover, although huge progresses in terms of vibrations reduction in the last couple of decades, there are still some vibrations linked to not perfect engine balance, which cannot be completely avoided. All of this is absent in EVs and other noise and vibration sources are suddently important. On the other side, new challenges had to be faced, as the disturbing high frequencies of electronic components (perceived as kind of whistle), absent in ICE cars. In summary, NVH demand is now higher and it requires much more efforts during the development.

1) Reduce the overall noise at the source. 2) Body sealing: do not let the noise in. 3) Design in stiff powertrain and chassis attachments to body. 4) Absorb, Sound Transmission Loss, and Damp (insertion loss) what noise remains. The closer you treat the noise to the source, generally, the lower the cost of the countermeasure. I have never seen a "treatment" (absorption, STL, damping) operate purely, that is some STL material adds some mass damping affect, etc. So, I would only and always look at Insertion Loss of a treatment and not go by a single mode measurement. This will lead you to fully trimmed vehicle on-road evaluation (validation). This might seem to complicate your development but it will result in the best value.

As a valuable tool for reducing NVH on automotive application is to perform FFT analysis on noise data aquisition in order to identify the main source of noise (vibrant panels and structure, engine and directly coupled fans,etc) and apply damping or isolation materials on regions close those areas (underneath hood, wrappers, firewalls,doors clearance). This certainly will help to reduce noise and vibration on key spots.

To reduce/prevent NVH some rules on design, also material are needing, like texture, ribs, thinkness wall, etc. this concept reduce resonance and propagation of the NVH frequência.

I totally agree with reducing NVH from the source. I took a leaf from Lexus and how they refine the ride: even acoustics of motors for example, are fine tuned to produce minimum sound..moving parts like propsfts , fans, should also be tested to cancel any would be booming.