Thread: Sound suppression?

Depends on the body type. If it is a closed body (cab or hardtop or wagon), floor mats, door liners, roof lining etc are a good start. Hardly worthwhile in a rag top as wind noise and flapping canvas will overpower just about everything else.

For any body, however, carefully go over the body, ensuring that there are no loose panels that can vibrate. Make sure that all the small holes into the passenger compartment are blocked - panel joins, door seals, unused holes etc. Even very small holes let a surprising amount of noise in.

Engine noise should be fairly small, provided that tappets are correctly adjusted. Transfer case noise seems to be inevitable, and should be the dominant mechanical noise. But in most cases, the dominant noise will be tyre and wind noise. Wind noise is minimised by reducing or eliminating any air leaks particularly round the doors. Tyre noise is pretty much simply a choice of tyres.

You are likely to find some distracting vibrations at particular engine speeds - I have two that I have yet to fix - one is the hand throttle, and the other is the radio installation - I know how to fix them, just haven't done it yet. A sheet of some sort of rubber on the bottom of the glove boxes will reduce rattles from the stuff in them.

Some form of sound deadening may be useful on the back of the seat box, floor and transmission tunnel, and perhaps under the mudguards to quieten the stones thrown up, but don't expect too much from ity.

Bonnet insulation will give a slight improvement, but just as important if you are doing this would be seals on the sides of the bonnet and at the back.

Fan noise can be noticeable, and replacing it with an electric one can help.

But the bottom line is likely to be tyre noise for most people.

John

Rare spares sell a 12mm cloth faced sticky backed insulation sheet. I fitted one under the bonnet and lined the floor with a bitumen 3mm sticky backed insulation sheet I got from them too. It is in my Defender but it made at least a 10-15 db difference in the cab. My old S3 (Smeg) was as noisy as with the hardtop on but I find Ralph (2a) with the soft top is actually quieter than Smeg. There is a guy in Melbourne that does Jag parts and he sells the same 3mm insulation at about 1/2 the price.

Cheers Ian

Bunnings (I avoid it if possible) sell a lightweight synthetic noise block material in sheet form, located in amongst the chipboard & craftwood. Actually looks as though it could be good for under floor mats and against the firewall etc. . Shouldn't be adversely affected by water ingress.

I just had a great club run in my 2a as a ute with no door tops or roof, completely open.
Even up to 110 kph I didn't think there was any wind noise, I could hear everything around me and most prominately was tyre noise from ugly fwd,s or semi's.
All the way through the speed range the cars own noise was minimal, on the day before I was even able to speak to my wife at normal conversation levels.
Totally different to riding in the car as a station wagon

Thanks for the tips.
For the firewall and floor etc, does the insulation material go on the inside or outside, WRT the cabin?

Jordan

The effectiveness of it will be similar either way. Which will probably largely depend on what you use. If it is on the outside, it needs to be reasonably waterproof, and on the firewall it needs to be heat resistant (and also for floor bits near the exhaust). Floor insulation on the outside needs to resistant to damage from sticks, stones etc.

Inside it needs to be presentable, resistant to kicking, tools etc, and to some extent waterproof, especially on the floor.

I have some dense rubber foam on the back of the floor and seat box, door cards, and rubber floor mats and transmission tunnel cover, but no firewall or bonnet insulation. Also have rubber or plastic foam roof lining (standard deluxe trim).

John

Earplugs.
Aaron

I went a bit overboard on sound insulation a while back. Yet to road test it. Send me a PM if you want any details on what I bought.

Cheers,

John