Thread: Sound Proofing & insulation on the cheap

I've got a radio in my series that I fitted when I was using the 2.25 diesel, and could hear it perfectly at speed.
What is more I only spent under $50 to achieve this.

I have looked at nearly all sound deadening materials being sold out there for big prices and I know you can do a lot better for a lot cheaper - even free! I've also studied the mechanics of sound transmission and worked out why these materials work. From there it was a short step to find similar common materials that worked just as well.

We cannot prevent the noise being created, but we can block, reflect or absorb the energy and reduce the amount of noise that reaches us.

Your firewall would do a good job of reflecting noise but with reflectors and blocking you have to have a seamless piece as the sound will get through gaps and holes. So – first job – Block holes and seal floor panel edges with foam tape. Window insulation strip is ideal.

Next problem – the metal is thin and any energy on one side will enter the metal and make it vibrate like a speaker cone. Resonance needs to be damped out and the only way to do this is to make the panel more rigid or add mass. Expensive products claim to do this, but I used 6” bitumen flashing band cut to fit the centre of panels ONLY. DO NOT go wall to wall with this stuff or you will just add weight. Also it’s no good upside-down in the heat. Small pieces are ideal to seal holes in the bulkhead.

Now the real find –
You need to absorb the vibrations from the bulkhead with something soft, and combine it with a hard dense layer that blocks the sound, and then add a soft layer again to absorb sound from inside the cabin. Again high-end products do exactly this, but for FREE you can too.
The answer is office floor tile squares. BUT you fit them the reverse side down, that is the carpet side to the bulkhead and the black hard side to the cabin.
I used Velcro hook strips 3” long stuck with impact adhesive to the metalwork, then cut the tiles using paper templates and just pushed them into place. The loop pile of the carpet holds them very well.
Then you have to tidy things up and use a spray adhesive to stick a thin decorative automotive carpet onto the hard tile backs. If you are careful with the joins you can remove them if they get wet.
I only needed to stick the very tops under the dash area to keep it tidy and neat, but could use alloy strips and fasteners. I did fit black alloy corners to protect the footwell to door area.
This combination of soft-hard-soft works very well.

Over the transmission tunnel I used 3mm rubber sheet cut for gearlever and 4wd just flopped over it, then fitted a carpet trim over that.

Seat bases got flashband inside it, rubber mat on top then carpet on the top of that.

The rubber mat I use is actually crumb rubber underlay they use under Astroturf, and is recycled car tyres – and usually free! Solid particles with gaps allow sound to enter it but not return. Very good at soundproofing. I use a load mat using it and on top of the seat base. I have also stuck it to the inside doorskins with neutral silicone. This improves the sound of the door closing – removes the biscuit tin sound and gives a firm positive clunk.
My other series already has a rubber backed industrial dirt trapper mat in it that I rescued from a skip. Pressure washers have their uses

Inside the roof I have used reflective closed-cell foam camping mats mounted with silicone dots. If you use lines of adhesive the water gets trapped so dots allow free draining. This keeps it cooler in summer – as does having a white roof.


Inside the engine bay is a difficult area as all items need to be fireproof – class O rated so I have only used second hand engine hood lining from a scrappies. Buy the flattest you can find, wet it, walk on it and let it dry out again. I used short roofing screws to screw the centre parts and back edge to the ribs and trimmed the edges before using silicone and tucking the edges in. It is short at the front, but this is only the radiator area so not much noise from that. Any saggy bits are stuck with silicone.

If you do get fed up with anything – silicone is more fun to remove than other types of glue and causes minimum damage. Just remember to only use Neutral cure types or it will stink and corrode.

Look out for people selling leftover bits of automotive carpet if they refit an RV as they often buy too much. I got mine like this and was enough for the front cab area. Carpet tiles are often thrown out or sold off very cheaply. We're not bothered about colour so should be free.

Originally Posted by Richie_asg1

...And with fabric carpet in place. The edge trim is just 2" wide strips of black vinyl used for seats etc. Oh you can see the vinyl handbrake gaitor in this one too. Modern rubber seems to crack too quickly.


And reflective mat on the roof

where did you buy the reflective mat? I have seen camping matt but not reflective like yours.
Cheers
Craig