Types of Car Sound Deadening Materials

Vibration damping materials are installed directly onto metal panels. They reduce resonance and stop the doors, floor, roof, boot and wheel arches from behaving like the skin of a drum.
This is normally the first layer in a professional soundproofing system. It is particularly important for low and medium-frequency vibration travelling through the vehicle body.

We currently use four main StP vibration damping products:

• StP Black-Silver for reliable and cost-effective vibration control;
• StP Aero when low weight and strong damping performance are both important;
• StP Gold for higher-performance soundproofing projects;
• StP Mass’a Bass’a for powerful low-frequency vibration, SPL builds and heavy bass systems.

The correct material depends on the panel, the level of vibration and how much additional weight is acceptable.

Some automotive soundproofing products combine several functions in one sheet. These are often called multi-layer, hybrid or sandwich materials.
They can reduce the number of separate layers required, save installation space and make it easier to build a complete soundproofing system in areas where there is limited room behind the original trim.
StP Bromo combines a dense sound-blocking layer with acoustic foam. It helps block low-frequency road and tyre noise while also absorbing sound inside the cabin. It is commonly used on the floor, under the seats, around the rear wheel arches and in the boot.

StP Sonora is designed mainly for inner door panels. It combines vibration control, sound absorption and moisture resistance, making it suitable for door cavities where water, airflow and limited space need to be considered.
Combined materials can be useful, but they are not automatically suitable for every part of the vehicle. The product still needs to match the type of noise, installation area and available space.

Sound-absorbing materials deal with noise that is already moving through the air.
Soft and porous materials allow sound to enter their structure, where some of its energy is absorbed instead of reflecting around an empty door, roof or boot cavity.

Absorbers are particularly useful for medium and high-frequency noise, including reflected sound, harsh frequencies and some interior rattles.

Materials such as StP Accent and StP Biplast can be installed behind trim panels, inside doors, under the roof lining and in other protected cavities.
They can make the cabin sound calmer, but they do not replace vibration damping or a dense noise barrier.

Sound-blocking materials create a dense barrier between the source of the noise and the passenger cabin.
They are mainly used against low-frequency road, tyre, engine and drivetrain noise entering through the floor, firewall, wheel arches and boot.
Materials such as StP NoiseBlock 2 add mass and reduce the amount of airborne noise passing into the cabin.

Combined materials such as StP Bromo can provide both sound absorption and sound blocking in one layer.
The three functions are not interchangeable. Vibration damping controls moving metal, absorbers reduce reflected sound, and dense barriers block airborne noise.
The best results normally come from combining the right materials for the frequency, location and source of the noise.

When a vehicle is moving, large metal panels vibrate due to the tyres, suspension, engine, exhaust and audio system. These panels can behave a bit like the skin of a drum, adding extra noise to the cabin.
A butyl mat helps control that movement. As the panel flexes, the butyl layer stretches and converts some of the vibration energy into a tiny amount of heat.
You can usually hear the difference with a simple knock test. An untreated door panel often sounds thin and metallic. After proper damping, it sounds more solid and less lively.

Butyl and other constrained layer damping materials for cars are commonly applied to:

• doors;
• the cabin floor;
• the transmission tunnel;
• the roof;
• the boot;
• rear quarter panels;
• wheel arches;
• the firewall, provided the material is rated for the expected temperature.

The mat must be installed on clean, dry metal and pressed down firmly with a roller. Dust, grease, rust and loose factory coating can all weaken the bond.
Sticking an expensive mat over a dirty panel is still a bad installation. Heat and vibration will eventually find the weak spots.

Butyl sound deadening thickness matters, but it should not be the only thing you look at.
Two mats with the same overall thickness can perform very differently. One may contain a strong butyl compound and solid aluminium facing, while another may use excessive filler and thin foil.

When choosing vibration damping material for cars, check:

• butyl compound quality;
• aluminium thickness;
• adhesive strength;
• heat resistance;
• flexibility;
• material weight;
• tested damping performance.

A thicker or heavier product may provide more damping, but more material is not always better. Covering every last centimetre can add unnecessary weight without giving the same improvement everywhere.
The correct coverage depends on the size, shape and stiffness of the panel. Large flat areas usually need more attention than small reinforced sections.
So do not choose a mat just because it has the biggest thickness number on the listing. That is a bit like choosing tyres only by how chunky they look.
A good butyl sound deadening mat should stay firmly attached, remain stable in heat and control panel vibration without adding more weight than the job requires.

Open-cell foam contains connected air pockets. Its porous structure allows sound to travel into the material, which makes it useful for acoustic absorption.

Open-cell foam car soundproofing can be effective:

• behind door trims;
• under the roof lining;
• inside rear quarter panels;
• around the boot;
• in other protected body cavities.

The material should not be compressed too heavily. If you squash it flat, you reduce the open structure that helps it absorb sound.
Open-cell foam sound deadening also needs to be selected carefully for automotive use. Not all foam can handle the heat, moisture and movement found inside a car.

Automotive sound insulation may also use polyester fibre, acoustic felt or other fibrous materials.
These products can fill larger cavities and absorb reflected sound without adding as much weight as a dense barrier. Some materials also provide useful thermal insulation, which can help keep heat outside the cabin.

Felt and fibre are commonly used:

• behind interior panels;
• under carpets;
• under the roof lining;
• inside boot side panels;
• around rear wheel arch areas.

However, moisture resistance is important. Traditional felt, jute and recycled fabric materials can hold water if they are installed in damp areas.
That can lead to bad smells, mould and corrosion. Doors are particularly risky because water naturally enters through the window seals and drains through the bottom of the door.
Any car sound insulation material used in these areas should be suitable for moisture exposure and should never block factory drainage points.

No. StP Accent can absorb some airborne noise and improve thermal insulation, but it does not have enough mass to block strong low-frequency road or tyre noise on its own.

Where sound blocking is required, we use a dense barrier such as StP NoiseBlock 2 as part of the selected multi-layer system.

Open-cell products such as StP Biplast are softer and more porous. They are mainly used to absorb reflected sound and reduce echo behind interior trim.

Closed-cell or polyethylene-based products such as StP Accent are more resistant to moisture and compression. They are better suited to doors, roofs and other areas where heat, limited space or moisture need to be considered.
For targeted squeaks and rattles, StP Bitoplast Tape is normally the more precise option.

StP NoiseBlock 2 creates a dense barrier between the noise source and the passenger cabin.
It is mainly used to reduce:

• road and tyre noise;
• engine and drivetrain noise;
• highway rumble;
• noise entering through the floor and rear wheel arches.

Unlike a vibration damping mat, NoiseBlock does not primarily control metal resonance. Its purpose is to stop airborne sound from passing through the treated area.
For the barrier to work effectively, the sheets need to form consistent coverage. Gaps around edges, cables, seat mounts and service openings can allow noise to pass through weaker areas.

We normally install StP NoiseBlock 2 on:

• the cabin floor;
• the transmission tunnel;
• interior wheel arches;
• under the rear seats;
• the boot floor.

It is installed as part of a layered soundproofing system rather than used on its own.
A typical system may include:

1. StP Gold or StP Aero to reduce panel vibration.
2. StP Accent, StP Bromo or another suitable acoustic layer, depending on the area.
3. StP NoiseBlock 2 where an additional dense barrier is required.
4. The original carpet and trim over the materials.

Each layer performs a different job. The vibration damping controls the metal, the absorption layer reduces reflected sound, and NoiseBlock helps prevent external noise from entering the cabin.

Butyl mats are normally used on accessible interior metal panels such as doors, the floor, roof and boot. They are cut to shape and rolled directly onto the prepared surface.

StP NoiseLiquidator is used mainly on exposed exterior areas where a sheet material would be difficult to protect or fit correctly. The liquid coating follows the shape of the wheel arch, seams and pressed metal sections, creating continuous coverage across the treated area.
It does not replace the interior soundproofing layers. Instead, it works from the outside of the vehicle and supports the overall system by treating one of the main paths for tyre and road noise.

Wheel arches are close to the tyres and are constantly exposed to water, mud, gravel and road debris. The metal can transmit both vibration and impact noise into the cabin.
StP NoiseLiquidator helps reduce these vibrations while adding anti-corrosion and anti-gravel protection to the treated surface.

The exact treatment depends on the construction of the vehicle. Metal wheel arches can be coated directly after proper preparation, while felt liners may require a specialised version of NoiseLiquidator before additional sound-blocking material can be installed.

Cars get hot, especially in Australia. Materials installed on the roof, floor, firewall and inside doors need to stay stable when the cabin temperature rises.

A low-quality adhesive may soften or lose its grip. Some cheap compounds can also produce an unpleasant smell in hot weather.

Doors, wheel arches and underbody areas are regularly exposed to water.

Materials used in these locations should not hold moisture or block factory drainage holes. Absorbent felt or foam may work well in a dry roof cavity but can cause trouble inside a wet door.

Dense materials can be effective, but they also add weight.

A full barrier installation across the floor, firewall and boot can become heavy. That may be fine for a touring vehicle, family car or luxury sedan, but it may not suit a lightweight performance car.
Use enough material to solve the problem, not enough to build a bunker.

Thicker material is not automatically better.

The available space behind trim, carpet, seats and door cards is limited. If the material is too thick, panels may no longer fit correctly or clips may not lock into place.
Quality, density and correct installation are usually more important than one large thickness number.

Always check how much room is available before installing several layers.

Door mechanisms, wiring, airbags, seat mounts and ventilation channels must remain clear. A soundproofed car still needs to function like a car.

Different layers need to work together.
A butyl mat should bond properly to the metal. A decoupling foam should support the barrier without being crushed completely. Adhesives and coatings should also be compatible with the surface and with nearby materials.

When in doubt, plan the whole system before installing the first layer. It is much easier than pulling half the interior apart twice.