Car manufacturers are addressing issues with increased noise, vibration and ride harshness in what the industry calls NVH. Some of this is normal, relating to spinning engines, tyre and wind noise, exhausts under pressure and suspension parts soaking up road imperfections. This is more pronounced in vehicles with off-roading in mind, especially larger and older utes and 4WDs. To drone out unpleasant sounds making their way into the cabin, drivers now have the same options as carmakers – sound-deadening materials. Done right, these provide for more comfort and quiet no matter what type of road you’re on.
Excessively loud clunking, popping, and grinding sounds are signs that there’s damage to suspension or drivetrain parts. CV and U joints at both front and rear axles, worn bushes, tired ball joints, gears slipping, and general wear and tear are some of the main culprits. And this needs repair or replacement.
Assuming your 4×4 is sound mechanically, and you’re still hearing whining and humming from the transmission, screeching from the tyres, rattling of panels or the exhaust, time to take the next step, and insulate your vehicle. Larger 4WDs and those preferred by Aussies for serious off-roading benefit the most. Toyota Land Cruiser sound-deadening products, and products for all 4WDs and utes sold in Australia are readily available at reasonable prices.
To get the best results, sound deadening products are applied in layers. They can be precut and sold as kits for specific vehicles or found in standard sizes and cut to shape for separate vehicle areas.
What is Sound Deadening?
In the broader sense, sound deadening (otherwise called sound damping/dampening) involves reducing the vibrations emanating from different vehicle parts. These are what produce sound and at louder volumes, resonance. Products are tasked to dampen and absorb vibrations at the source, and serve as a barrier. This is done with a combination of materials.
Sound Deadening Products
The first stage of sound deadening involves the use of a butyl rubber noise absorption layer with an aluminium layer to add structural stability and span gaps and openings in panels, doors, and other body parts. Butyl rubber is applied to the floor pan, rear firewall, roof, and door skins. It is pressure sensitive and sticks easily. In addition, it’s not prone to rotting and crumpling like older tar or bitumen sound-deadening materials.
The thickness of butyl (around 2mm) isn’t quite enough to drone out all sounds. Car manufacturers today use Mass Loaded Vinyl (MLV) as an addition to butyl rubber. MLV serves as a sound blanket and lends mass to the rubber layer underneath. It is a heavy limp sheeting material that’s also dense but flexible, making it relatively easy to apply and line into floor pans and firewalls.
If there’s additional space, a specially-formulated acoustic liner is placed on top. This is thicker (at 12mm) and consists of two layers. The backer material is a closed-cell foam with a self-adhesive, and the facer is an open-cell foam for breathability. The combination replaces traditional jute or cotton lining and is better in every way. It doesn’t rot, nor attract mould, and sticks easily. Besides serving as a sound barrier, this material is also water and heat resistant so no radiant heat makes its way into the cabin. It is ideally placed in the firewall but is also used inside cavities and door panels.
To deaden rattling noises in your 4WD’s roof, as well as reduce heat, a thinner (3 or 6mm) sound layer with self-adhesive is used. This is a simple closed-cell ‘peel and stick’ insulation foam that easily adheres to the uneven surfaces in the roof lining. It can also be used to separate butyl rubber and MLV in floor pans and firewalls.
Is Sound Deadening Worth It?
Sound deadening products are cheap for what they offer. There’ll be less noise coming in from rattling panels and loud engine and transmission parts. Cabin comfort is significantly better as a result. You won’t need to shout to have a normal conversation, nor crank up the volume on the radio to hear a decent tune. In addition, there’ll be less heat making its way in. Add to this the waterproofing, and prevention of rust and mould, and the entire process soon pays off.
Are Sound Deadening Products Applied in a Particular Order?
The short answer is yes. First is the butyl rubber layer that lines the floor pan, followed by the MLV layer and then the acoustic lining which doubles as carpet underlay. Once this is set you can fit the carpet. Butyl is the first line of absorption, the dense MLV layer blankets out stubborn vibrations and rattling, and the acoustic liner in the twin foam construction completely blocks out what’s left. Knowing where sounds originate can help in using one or all sound-deadening products.
Do You Need to Buy Products Separately?
Buyers can choose to get sound-deadening products separately, and in the quantities needed. There are however complete kits available, like Land Cruiser sound deadening combos, also offered with the basic tools for quick installation. These can save you quite a bit if you’re considering stripping out all the old underlay and insulation. If you need to deaden the noise from particular areas like the roof, then separate sound dampening products are the way to go.
Either way, you will considerably reduce noise and heat levels in the cabin. And can do all the work yourself. Sound deadening products are easy to get right even for complete beginners and without making a dent in the back pocket.