HOW TO soundproof a LR Defender

[dado.mago]

Hi Landies, hope you’ll find this helpful.

Like all the Land maniacs, I spend most of my free time to fix my truck and to improve it, and because I found here and in other forums lots of useful info, it is the time to give some help back.

As many of you, I got to the point where I cannot stand anymore the extreme noise of my Def coming from the engine, gearbox, transmission, and mud tires.
For what concern the tires there is no solution unless you choose to change tires.

Before starting with the job, I read lots of posts, articles, technical papers about the right material to use for this purpose and the causes of the Pratt&Whitney noise in the cabin when you drive over 100 Km/h, and the conclusion is that other that the real noise coming from engine, gearbox, transmission, tires, the high dB level is caused by the vibration of the body of the truck, and furthermore the big volume of the cabin amplifies the noise (noisier in the 110 than in the 90; bigger the sound box, higher the noise).
Hence it is better to put any mat inside rather than outside the cabin in order to break the vibrations.

So I surfed the web and I read lots of posts in different forums all over the planet, and I found a few websites that promote a “noise killer kit” like this Landrover Tuning :: Defender 110 FULL Noise Killer Kit, Sound Proofing,Tdi, Td5, Td4, Engine Blanket Optional

Actually I think it is too expensive, especially for the materials used, and looking to the photos it didn’t convince me especially for the thickness.
Because of my job it came to my mind straight away that for sound proofing and to reduce the heat transfer the best one material would be neoprene, so I found a warehouse where they sell any rubber material and I bought 5 sqm of 6mm neoprene membrane for 100$ (obviously cash, otherwise would be more than double the price), a good compromise thickness/mass (bigger the mass and noise frequency, higher the dumping).

First of all I removed the front seats, the cubby box and all the original rubber in the front of the cabin. If you don’t have aircon in your car you could try to remove the front panel and dashboard, but for me was barely impossible because of the aircon unit the previous owner installed, and because there is a pipe to the engine, there is a huuuuuge penetration through the front firewall, and obviously most of the engine noise comes from that hole.

Once you have removed the seats and so on, you will see a panel under the cubby box used to access the gearbox from the top, it is a 1mm aluminum panel, and whe I removed that I was surprised to see directly the gearbox and the transmission, I was expecting some kind of sandwich panel to absorb the heat and the noise, but clearly they preferred to stick to the original design of 1948! Any improvement was out of question.




then I started to cut the neoprene in medium/small pieces and I glued them using a “liquid nail” (just because I found an offer at Bunnings and I was terribly late, but eventually it turned out to be very good because it dries in 5 minutes, so you don’t need to keep the pressure on the membrane for all the night to wait it dries).



It is better to cut the neoprene sheet so that you don’t have to bend the membrane at the corners, but just glue them together at corners .




Than I glued the neoprene membrane around the gearshift, the driving pit and passenger pit, on the battery and computer cover plates, whereas over the remaining area under the cubby box it is better to provide a continuous sheet of neoprene so that you will prevent the noise and the heat to come through the gap between layers.
Be careful to lay the membrane up to the border of the pit so that when you close the cover it will press the membrane sealing the pit; the same for the computer pit.
(PS green=slot in; red=glue it; balck=just lay down)






Because I have the additional aircon unit as I said, it was impossible for me to put the neoprene on the firewall, that’s why I put the membrane in the inner face of the engine bay. No worries, there is no danger, it won’t melt, neoprene can resist up to 600°, and the engine bay won’t reach that temperature.
In my case I put lot of neoprene to seal the big penetration of the aircon pipe.


As last step I put the neoprene on the underside of the bonnet so that the noise from the engine is reduced, especially when you open the flanges under the windscreen to let the air flow in.




I suggest for the front and back foot wells and the boot not to glue the membrane to the body because if it gets wet you won’t be able to take them off and dry them.
For the rear seats and boot, it is enough just to lay down the membrane without gluing it.






After the job (1 day) you will appreciate the silent……ok, it is not a Rolls Royce, but neither a M1 Abrams tank!
The noise is less than 50%! trust me.

[Chops]

Good job DM,
I've been watching another thread on the same subject, just waiting to see the final outcome.
This mating you've used could be a good alternative for those of us with a tight budget.
Thanks for sharing.

[Tombie]

Neoprene will help, but for best results heavy material like bitumen impregnated sheeting, lead lined etc will provide best results.

The bitumen material is also better suited for floor areas where there will likely be water as the Neoprene can (will) hold the moisture against the panel causing corrosion.

[Bundalene]

You came up with a very similar concept to ours with a different product. I think your bonnet liner will make quite a difference though.



Reducing heat and noise levels.




We found great results were in the heat reduction in the cabin.



Erich

[Judo]

Great job and thanks for posting photos and sharing! I've been researching materials for my Isuzu and current thinking is this:

http://www.acousticsandcoatings.com....35%20flyer.pdf

By way of comparison, it's around $50/sqm. So 5sqm (what you bought) would cost $250.

[dado.mago]

Neoprene will help, but for best results heavy material like bitumen impregnated sheeting, lead lined etc will provide best results.

The bitumen material is also better suited for floor areas where there will likely be water as the Neoprene can (will) hold the moisture against the panel causing corrosion.

Yeah, for sure, to be honest it would be better to include an extra thin lead plate to cut off the higher frequencies, but obviously it becomes a matter of price, thickness, and time consuming.
It would be good to test different systems on the same truck to understand the different performance, but to me the 6mm neoprene membrane worked superfine , I just spent 1 day and the result is astonishing, now the noise is reduced more than 50%! I am not joking , and the cost was 100$!

[dado.mago]

Great job and thanks for posting photos and sharing! I've been researching materials for my Isuzu and current thinking is this:

http://www.acousticsandcoatings.com....35%20flyer.pdf

By way of comparison, it's around $50/sqm. So 5sqm (what you bought) would cost $250.

It looks a good product, but it looks thick (more than 6mm), and I don't really know the range of the noise frequencies. I just guessed that the range of frequencies in play could roughly be absorbed by the neoprene, and my guess was right. To be honest I didn't expect such a good result, I was aiming to a reduction of about 20%, for sure not more than 50%! but I was lucky.
The guy who sold me the neoprene told me the price is 180$ per 2sqm sheet, but I guess he had few sheets in the wharehose to get rid of so he gave them to me 5sqm for 100$, and if u tell him u r gonna pay cash I think he will probably make a deal.......for him first
If you need the address, just ask.
Cheers

[SimonM]

How will the neoprene cope with the heat in the engine bay?

This is a job I want to tackle myself soon. Thanks for posting.

[manic]

Neoprene will help, but for best results heavy material like bitumen impregnated sheeting, lead lined etc will provide best results.

The bitumen material is also better suited for floor areas where there will likely be water as the Neoprene can (will) hold the moisture against the panel causing corrosion.

Yes I agree.

If you are going to be sticking it in permanently then bitumen sheet as a base layer (it bonds very well and does not let water get underneath), then a layer of neoprene (it is closed cell and should not absorb water). I wouldn't stick the neoprene down, instead lay heavy rubber matting over the top. You can then take the rubber mats out and remove the neoprene if you need to clean out. The mats protect the neoprene and the neoprene helps protect the foil of the bitumen from getting ripped.

If you do not want to bond anything at all you could do just as well without the bitumen on the floors and just have neoprene pushed down onto the panel with the weight of heavy rubber matting - which will probably dampen the panel as effectively as bonded bitumen.

The OP knows that the boxy defender with all its hard surfaces can really raise the harshness of the noise. Soften all panels and you will soften all the sounds. IMO a single 6mm layer of bonded neoprene would give a more pleasant sound reduction than a single layer of bitumen foiled sheet (aka dynamat).

[dado.mago]

How will the neoprene cope with the heat in the engine bay?

This is a job I want to tackle myself soon. Thanks for posting.

Hi Mr Ploppy, it copes very well, it never showed any kind of melting or damage. I was worried as well at the beginning because I didn't know how reliable was the information about the admissible temperature of 600°, but I have to say that it works very well, even in those weeks last months of continuos 30-35°, it didn't show up any problem. Anyway, the engine bay never goes to 100°, it ususally goes not more than 80°, so we are safe.