Cars have come a long way since WWII, but they haven’t really gotten any more enjoyable, which is why we all still like to play with our old cars. Plenty of people will argue about whether a new Honda Accord could beat a first generation Mustang in a race (it probably would, no matter whether a drag strip or a road course), but no one is going to argue about how much quieter it is inside the modern car. Sure that’s both good and bad; we want to hear the 289 roar, but that freeway drone gets old after an hour or two.
Luckily for us old car hobbyists, only a small portion of the passenger compartment noise vibration and harshness elimination in a modern car is deigned in. Most or the comfort and quiet you experience in the driver’s seat comes from add on products you can apply to any car. One of the easiest to apply is sound deadening paint. Do it right and cover all the bases and you could be one of the few people cruising a pony car in Lexus level quiet.
Large flat metal panels can “drum”; small hits can be amplified and spread by the panel. Unless your vintage car of choice is a VW Beetle, you likely have many large flat panels. Luckily drumming is easily fixed in things like roofs and the trunk lids. Covering 25-50% of any flat panel with CDL tiles typically stops most of the annoying noises and give your car a nice solid sound.
“CDL”- Constrained Layer Dampener, an adhesive backed layer of rubber with thin aluminum on the back. Both Dynamat and Eastwood’s own X-MAT sound deadener can be used as CDL tiles. Of course using it this way only works for sound, in order to get the thermal benefits you need as much coverage as possible.
But what about areas that aren’t flat? What about places you can’t reach to install a mat, like inside a door? Luckily there are products that do the same job, but can be brushed, rolled or sprayed on. Sound deadening paints, such as Lizardskin, Boom Mat Spray-On and Eastwood’s own Flexible Sound Deadener.
All of these products can be applied inside doors, quarter panels, rockers, and the underside of trunk lids and hoods to change their sound characteristics for the better. You can even apply them inside frame rails, and A, B, and C-pillars, thru almost any small hole.
With the right tools you can spray these almost anywhere, even places you can hardly see. Lizardskin offers an air gun with a nozzle that can literally shoot around corners. Eastwood’s aerosol spray Flexible Sound Deadener can be applied via a 24” hose mounted nozzle, thru a tiny hole, to do the insides of rocker panels, frame rails and pillars. If you are going all out with a frame off or rotisserie restoration, you can spray Lizardskin ceramic insulation and sound control directly to the bottom of the car for a cool quiet ride.
No special prep is usually needed for these coatings, they go on just like paint. Just clean and degrease the area to be coated, or as much as you can reach, and apply like any other paint. All of these products have great protective properties and can be applied to bare metal even, to prevent corrosion. The thicker you apply it the more sound deadening you are going to get out of it. You can even top coat it with a paint of your choice for a more finished look to parts you see.
The benefits of the liquid spray, brush or roll on sound control products are pretty easy to see. Peel and stick mat materials need to be cut, fitted, and then stuck to the nooks and crevices of your interior, trunk and engine compartment. Paint on products can be applied in almost no time at all, once you mask things like windows and the dash. Liquid products can also be applied blind in places that aren’t easy to reach. Also, while acoustic mats are pretty flexible, there is no way to get a tighter fit than painted on. Painted on sound control products typically add less weight to the car too.
The down side is that mat type materials, when fully applied, do a better job of noise control than paint on solutions. But they had better considering the extra work it takes to install them. How much better, and is it worth it? Only you can answer that one. But know this, you can only make the rest of the body panels as quiet as the windows. Unless your car is a Mercedes with the double layer practically soundproof glass, and you always keep the windows up, they will likely be about the same.