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Noise insulation/Sound deadening

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ChrisH

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Our 1989 R4 GTL, LH drive bought in France, suffers heavily from road noise, but there is nothing at all under the rubber floor mats. It's so noisy on some road surfaces we need ear defenders!

Back in the mid 1970's we had a 1973 850 R4 which I am sure had some under rubber floor mat material; certainly we remember the car being much quieter than our 1989 car, noise was never an issue.

It maybe that Renault considered sound deadening to be an issue in the UK and fitted it, but not in France so didn't fit it?

Anybody fitted sound deadening under the floor mats, and if so, what? From where? And how expensive?

Regards, Chris
 
It must be all the extra noise from the extra few HP you get with the 1108 GTL engine! You could try old carpet.
 
Sorting out the door and tailgate seals will make a difference. Soundproofing won't work until the sealing is good. Sealing the engine bay (holes in grommets in the bulkhead) also helps a lot.

If you want to fit something below the mat a thin layer of foam is effective. That has the effect of holding the rubber mat off the floor so when the floor vibrates the rubber mat is isolated and does not pass vibration (noise) into the cabin. Wouldn't bother with bitumen based damping materials - the lightness of the R4 floor means these are not necessary.

A massive noise reduction can be had by gluing 6mm open cell foam to the cabin side of the headlining. There is nothing in a GTL to absorb noise, so once it's in it rattles around the cabin and doesn't decay quickly. Carpets on top of the rubber mats would also help with this.

This is all theory from other cars (guess what I do for a living). Planning to try silencing a R4 when I get my Gordini on the road.
 
I have some foam insulation from camping - when you insulate yourself from the ground. Might try that!
 
Closed cell foam is ineffective for sound insulation. Open cell foam is the stuff to go for. It sucks up water like a sponge sadly.

Upholsterers might be worth a shot - they use open cell foam foam behind leather coverings, but it's only 30kg/m3 density. Otherwise Wolleys sell a few different types of foam and headlining. I did once come across a 1/4 inch thick foam intended for tractor acoustic headlining which is perfect as it is fairly dense at 60kg/m3, but open cell. I've not been able to locate it since.
 
The other place to try is a boat chandlers, I managed to get some great sound insulation from my local chandlers.
 
That's panel damping. Unlikely to have much effect unless sealing and sound absorption material had been added first.
 
That's damping material too. Constrained layer so quite effective for heavy panels. Not much cop for Renaults though.

Generally it's difficult stuff to specify on a car without testing. It can move the noise around a structure, so might increase noise as well as reduce it.

The foam and rubber stuff seems difficult stuff to find. Maybe "Clementine's Soundproofing Shop" could be a recession busting idea. I'll have a look about to see if I can find anything sensible on-line.
 
Bingo! :D

On this page: http://www.noisekiller.co.uk/materials.php Anything with foam in it would help a R4. The engine bay thing is just foam with a covering to keep water and oil out. That'll help reduce noise at source a little.

The one with the lead inside two layers of foam is a bit old fashioned (modern versions use a single layer of foam with rubber instead of lead, and the R4 already has the rubber in the floor mats so open cell foam by itself would work just as well.

Personally I'd find 10mm open cell foam at a density of 60kg/m3 and place it under the floor mats. In my early car I'll go for similar behind the head lining. I also feel something on the cabin side of the bulkhead might help. I'd prefer 12mm foam with a rubber backing that faces into the car. The damping sheets from the earlier links might work, but I suspect they would cause booms. Could be worth a shot.

Planning a fiddle when I do mine. I have some measurement equipment. Though it's difficult to test the damping as the glue is very good and the stuff is very difficult to remove.
 
All materials listed in this post seem to be water-absorbent. Have you experienced with something that does not retain moisture? Like bitumen sheets? I always wanted to fit sound deadening material on the R4 floor but was always thinking it would be not too good an idea if it retained moisture.
 
Hi,
Just to say to all who have chipped in with suggestions and comments, a belated thank you for your efforts.

Have been away for a while and not checked the forum until today - much appreciated.

Chris
 
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