Sound deadening refers to specialized acoustic damping materials that are applied within vehicles to reduce unwanted noise, vibration, and harshness, commonly referred to as NVH. These Sound Deadening products, such as Dynamat, Second Skin Audio, and Noico, are installed on metal vehicle surfaces like door panels, floors, and the firewall to limit the transmission of vibrations throughout the automobile structure.

Sound deadening materials work by adding mass load to vehicle surfaces which helps absorb vibrations before they can propagate through the metal body. This mass loading effect dampens the vibrations caused by road noise, engine vibration, exhaust drone, and other sources. Properly installed sound deadening can lower the noise level by up to 15 decibels according to independent testing.

Some key facts about automotive sound deadening:

It is applied as self-adhesive sheets, rolls, or butyl-based patches
Thickness typically ranges from 1/16″ to 1/8″
Most products are poly-vinyl-chloride (PVC) or polymer-based
Higher quality sound deadeners use multiple layered damping compositions

Where is Sound Deadening Typically Installed?

Several key areas in vehicles are targeted for sound deadening installation:

Door Panels

As one of the largest hollow metal structures, doors are a major source of booming and vibration. Properly damping the inner and outer skin can reduce noise by 50%.

Trunk/Hatch Area

The rear cargo area vibrates and radiates sound if not treated. Damping the floor and sides of the trunk significantly cuts down road rumble.

Under the Hood

Engine vibration passes through the firewall into the cabin. Dodo Sound Deadening the firewall and surrounding metal structures helps filter out engine noise.

Floor Pans

As with doors, untreated floor panels act like an echo chamber. Damping floor pans and transmission/drive shaft tunnels block noise.


In addition to damping the firewall directly to block engine noise, sound deadening the airbox, battery tray and other components mounted to the firewall further reduces vibration transmission.

Rear Deck/Parcel Shelf

Excessive booming from the rear window area is dampened by treating the rear shelf panel underneath packages and cargo.

How Does Sound Deadening Work?

The key to how sound-deadening materials are effective is through vibration-damping properties. When a vehicle is in motion, constant vibrations are occurring throughout the chassis and body panels from both exterior sources like the road as well as interior sources like the engine and exhaust.

These vibrations cause metal body parts to resonate at specific frequencies, much like a subwoofer enclosure. The resonating body panels then radiate the unwanted noise into the cabin. Sound deadening works to stop this vibration and noise transmission process in three important ways:

Mass Loading

By applying additional mass in the form of sound deadening sheets, the structure’s natural vibration frequency is lowered. This makes it less prone to resonate from outside vibrations.


The viscoelastic polymer or butyl compounds in sound deadeners absorb vibration energy when the panel vibrates. This keeps the energy from being radiated as noise.


When installed between two surfaces, like a door skin and framework, sound deadeners physically separate and isolate the surfaces. This prevents vibrations of one part from transferring to the other.

The combination of increased mass, vibration damping, and decoupling allows sound deadening to dramatically reduce the transmission of noise throughout the vehicle body. Some high-end products even use multiple layered compositions and foam backing for optimized damping performance.

Why is Reducing Noise Important?

There are several key reasons why reducing noise through automotive sound deadening is important:

Improves Comfort

Excessive noise inside the vehicle cabin creates fatigue over long drives. Sound deadening helps create a more relaxed, comfortable driving experience by damping booming, vibration, rattles, and other irritating noises. Passengers will appreciate being able to hold a conversation without yelling.

Increases Audio Quality

Road noise and other ambient vibrations can easily overwhelm a vehicle’s stereo and make it difficult to enjoy music or phone calls. With less vibration transmission through the body, the quality of sound from the audio system is dramatically clearer and crispier.

Preserves Resale Value

Future buyers will likely appreciate the quieter ride provided by sound deadening during test drives. It’s an inexpensive upgrade that could potentially earn owners more money when reselling or trading in their vehicle later.

Legal Requirements

In some jurisdictions, vehicles with aftermarket exhaust modifications or performance parts may be required to provide proof of additional sound deadening installation. This ensures noise emissions are still within legal limits on public roads.

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