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Now that you’re aware of all the different places noise can be coming from, let’s take a look at the different types of soundproofing materials. There is no one-size-fits-all material for soundproofing as different products are designed to solve different problems. For optimal sound quality inside your car, you’ll want to use a variety of materials in combination with each other.

Sound Deadening Materials

Sound deadening mats (sometimes calling vibration damping mats) are the basic product for reducing noise in vehicles. The core principle of sound deadening is to adhere a material that will resist vibrations to metal surfaces that are resonating sound. The soft material will damp vibration energy and dissipate it as low-level heat, reducing the strength of the metal's vibrations. The best material for the job is a high-quality butyl rubber combined with a foil constraint layer. At Second Skin, we use our cut, peel and stick Damplifier™ and our twice-as-thick Damplifier Pro™ sound deadening material. We also have great liquid applied sound damping and deadening products, like our Spectrum Spray On Deadener.

Apply the sound deadening material to the interior of your vehicle: under the carpet on the floor pan, on the firewall (engine side or cabin side), on the roof, and inside the trunk and door panels. You get a double benefit from putting Damplifier Pro™ mats underneath the headliner on the roof because it's also excellent for car roof thermal insulation.

Because our Damplifier™ products also act as a thermal insulator, they will block some heat transfer as well. Less noise and lower temperatures can mean a big increase in comfort, but keep in mind that sound deadening mats are only one part of the solution. While they are great for dispelling structural noise, they do not block or absorb airborne sound waves.

An illustration of vibration damping: without a sound deadener the spring's oscillations maintain their strength

Sound Blocking Materials

To wrap your head around sound blocking, think about a soundproof room. Special sound blocking (not deadening) materials have been installed in the walls and the door is sealed airtight, all to prevent unwanted sound waves from finding their way in or out. For automotive soundproofing, you won’t be able to shut out everything because the car’s windows will always be a gap. You can, however, apply the same sound blocking principles to key areas of the vehicle and block a large percentage of the unwanted sound waves.

What sound waves would you want to block out? A big one is road noise coming from underneath your car, especially the hum and droning noise that is made by the tires. The other types of noises you want to block are mostly mechanical noises: engine noise under the hood, exhaust noise from under your feet. To block noise, we’d recommend a automotive sound barrier product like Luxury Liner™ or Luxury Liner Pro™.

Luxury Liner Pro™ is our best noise barrier and one of our most popular products. It combines a mass loaded vinyl barrier layer with closed cell foam that acts as a decoupler and thermal insulator, making it a 2-for-1 product that’s much easier to install in your car. Luxury Liner Pro's decoupling foam prevents the MLV's surface from resonating with the sheet metal of your car.

Using Luxury Liner Pro™ will give you a massive step up in noise control over sound deadening mats alone. Using those two products together is the best combination for eliminating unwanted noises, whether you have an expensive audio system or if you just want a quieter, more comfortable cabin.

Noise barriers become more effective in a linear relationship with the material's density

Sound Absorbing Materials

Sound absorption materials are typically foam products designed to trap or absorb airborne sound waves. There are two types of foams: closed cell foam and open cell foam. Closed cell foam is not great for absorbing sound, although testing shows it will absorb some low frequency sound waves (road noise, machinery). Open cell foam absorbs mid to high frequency sound waves and is the product you’re thinking of when you imagine the foam in a recording studio. All of our foam products are good thermal insulators as well, so utilizing them also gives two-for-one benefits.

Our OverKill™ products (closed cell foam sheets), Mega Zorbe™ (open cell, hydrophobic melamine foam), and Heat Wave Pro (treated jute insulation) are all able to absorb sound and insulate from heat. Closed cell foam works best as a decoupler (shove it behind your plastic paneling), but is also a good insulator. Jute is your typical OEM solution, and is a middle of the road sound absorber and top-notch thermal insulator. Open cell foam will absorb a high percentage of sound waves, but we've upgraded our version to resist water and have improved thermal properties. Even though each product has its specific use cases, a good general rule is that the foam needs to be exposed to the interior environment (can't be covered by another material) to provide effective acoustical absorption. Fortunately to get the benefits of heat insulation, it can be behind the upholstery or plastic paneling.

Open cell foams will reduce echoes by absorbing sound waves, especially at mid-to-high frequencies

Depending on the area of the car you’re soundproofing, installation can range from a straightforward project you can tackle in a Sunday afternoon to something… a bit more complex. All in all, there’s basically four steps with every soundproofing project.

1. 1. Find the noise
   2. Strip the area
   3. Clean the sheet metal
   4. Apply your material - sound deadening layer applied to the metal, then sound blocking layer

We’ve been doing this a long time, so we’ve seen it all. We’re here to help you with your car soundproofing projects. Have questions? Give us a call or email us. We’ll help you find the right soundproofing and insulation materials. We'll also walk you through how to install any products.

Step 1: Find The Noise

Drive around and identify where the noise is coming from. Is it outside noise from construction and other cars? Or is it road noise making its way up through the floor of your car from the pavement? Listen for rattles and shakes coming from the doors or trunk. Honing in on where the noise is coming from will help you determine the types of material you need and the placement.

Step 2: Strip the Area

Soundproofing is all about coverage, and that’s hard to achieve when there are parts, carpet, wires, and everything else in the way. Safely strip down your car until you get to the metal. If it’s removable - take it out. This will make it far easier to apply material later on.

Step 3: Clean the Sheet Metal

Like looking under the couch cushions, you’ll be amazed at what you find underneath the carpet and parts of your car. Thoroughly wipe down and clean the sheet metal with denatured alcohol. The soundproofing material may be very sticky on its own, but doing this step will increase the bond strength. Besides, there’s probably at least a few dollars worth of quarters down there.

Step 4: Apply Your Material

Like we said earlier, coverage is key. Sound and vibrations are like water and will move through every crack and gap available. For sound deadening material being applied directly to the sheet metal - leave it out the sun to make it more pliable and then use a hand roller to ensure that it sticks to every corner and crevice. Any air bubbles you leave will substantially reduce the mat’s effectiveness. With thicker materials make sure you have enough clearance for the materials to fit. Also, don’t leave gaps and seal edges with foil tape. Fewer gaps will reduce the space noise has to get through and sealed edges protect from consistent water exposure.

Ok, so that was a lot of information but we’ve seen how a quiet car ride can transform your driving experience, so we developed a slew of solutions for everyone. This guide was about cars, but the same principles apply to truck insulation and van sound deadening too. We also have customer examples on our customer projects page, and we highlight some of our most popular models there, like our Honda Accord road noise  and our Honda HRV noise reduction article.

We hope this guide helps you get a better idea of the kind of solution you need, but if you still have questions you can contact us anytime - we love talking shop. Whether you want to discuss materials for your soundproofing project or the cost of soundproofing a car, or just bounce ideas off someone, shoot us a message with your situation and we'll get back to you!