A Simple Guide to Car Sound Deadening

Protecting your car inside and out extends longevity, ensures consistent performance and makes for comfier and safer journeys. New cars are becoming safer with every subsequent model. And the addition of different sound-deadening products also means they’re a lot quieter than cars from a decade ago. Manufacturers have gone to extraordinary lengths to make cabins whisper quiet and limit common noises, such as engine, tyre and wind noise spoiling an otherwise pleasant ride.

Much of the technology for reducing sounds and vibrations comes from high-end luxury cars. With an entire automotive field – NVH (Noise, Vibrations and Harshness) dedicated to reducing decibels inside the vehicle, engineers have made innovative and one-off sound-deadening products now available to a wider driving public. The good news is that you don’t have to spend thousands on effective automotive insulation and sound deadening.

Sound Deadening vs. Damping – Know the Difference

To cut the confusion, different car soundproofing materials do different things. The basic distinction is between sound deadening and damping. Deadening refers to the use of materials to absorb or block sound waves, thus preventing sounds and noise from spreading to other areas of the car. Common materials used in deadening, such as butyl rubber mats with aluminium top layers, reduce noise transmission by turning sound waves into heat or dissipating and reflecting sound to the source.

Damping or dampening also deals with unwanted noise. However, damping materials do this by decreasing the size and duration of vibrations. Acoustic foams like mass-loaded vinyl and sound vibration dampers add mass to vibrating surfaces to minimise rattling and noises. Both deadening and damping materials can be combined for a greater effect and a quieter car interior.

More about the Materials Used

Butyl Rubber Mats

These are some of the most effective sound proofing materials. They have replaced older bitumen-based mats which are known to degrade and crumble over time. Butyl mats have pressure-sensitive backing that sticks to uneven and irregular surfaces, and a top aluminium foil layer to stop soundwaves from spreading to adjacent parts. The material is thin, easy to cut and shape and withstands heat and water. It’s also odourless, doesn’t rot and comes in silver or black for added looks. Ideal uses are under carpets, in firewalls, roof lining and cavities and the boot.

Mass Loaded Vinyl (MLV)

An industry-standard acoustic barrier, MLV is a dense yet thin and flexible soundproofing material ideal for damping purposes. Recognisable by its dark grey colour, it’s made of PVC sheet and loaded with barium or calcium silicate to add weight. Thickness ranges between 2 mm and 5 mm and effectively deals with engine, transmission and exhaust noise. Ideal uses are in floors, firewalls and boots in vans, 4WDs, and older vehicles producing more noise.

Foam Insulation

Thicker closed-cell foams can be combined with butyl mats and MLV for extreme soundproofing. With thicknesses averaging 6 mm to 8 mm, this is an acoustic layer that also stops the spread of heat and moisture. It too is easy to cut and apply, won’t rot or attract mould, is lightweight and fits comfortably inside cavities, doors, roofs and in trim and quarter panels.

Sheep wool is also used in automotive insulation and sound deadening as it’s a natural, fire-resistant and odourless product sourced in pre-cut batts and used in roofs, boots and doors. Other materials include pre-formed deadening panels designed for specific makes and models, rubber or asphalt-based spray-on insulation applied directly onto areas like the wheel wells and undercarriage, and insulation tapes used in lining and joining individual pieces, and preventing thermal gaps.

Benefits of Soundproofing Products

Easy to apply, effective and affordable, soundproofing products bring a whole host of benefits:

• Improved comfort and ride quality – By reducing sounds, vibrations and heat reaching the cabin, mats, foams and acoustic barriers improve comfort on both shorter and longer journeys. They lower engine, tyre, wind and external noises, prevent higher temperatures and isolate noise from droning exhausts or loose panels. This versatility is a boon in all vehicles, ranging from smaller hatchbacks to larger utes or vans.
• Noise reduction – The obvious benefit, allowing drivers and passengers to listen to their favourite songs, have civil conversations, and reduce noise-induced fatigue. With materials targeting specific vehicle areas, noises and vibrations are greatly reduced.
• Fewer distractions – Unwanted and unexpected sounds can defocus drivers. A quiet cabin also means a safer ride and fewer distractions that draw your attention elsewhere.
• Improved heat and water resistance – Besides deadening and damping sounds, materials also reduce temperatures from hot engines or exhausts, provide a dry and water-resistant underlay for carpet and deal with common vehicle liquids, debris and stains from damaging electrics or rusting the metal.
• Increased resale values – Get the luxury car feel with soundproofing done right. Potential buyers will appreciate the work you’ve put in, meaning you can recoup more cash towards your next purchase.