I've decided that I want my Coupe to be a bit more civilised, so I'm having a go at soundproofing it with proper sound-absorbing closed-cell foam

It's a horribly fiddly job, especially as the foam is self-adhesive backed, with the second stickiest substance known to man (the first being the stuff that holds the rear light rings in!)

Anyway....

Will need to re-seal the Pininfarina badges before I fit the foam

Standard Fiat ant-vibration stuff is useless - it's falling off or curling up

Driver's side rear quarter panel done

rear quarter inside skin done, plus rear seat back panel

I've also done the parcel shelf, but forgot to take a photo

Still to do...

Rear seat base
Boot sides and floor
Rear seat back - inside the boot
Rear parcel shelf underside
Door skins
Door inner panels
Footwell , inc arches


I've bought four 2m x 1m panels of self-adhesive foam - 2 sheets of 12mm, one sheet of 6mm and one sheet of 3mm - should be more than enough

Review once its done, with the possibility of a group buy later

Nice. One thing I will point out is that I've read that it's better to overlap the CC foam rather than but the edges together.

Are you going to do the roof and lift the carpets up?

I brought a load of cc foam in my garage that I brough early this year to do the job but I haven't got round to doing it yet. So I look forward to your review.

I will be interested in the results. I'd like to lower a little of the road noise, but keep the engine and exhaust noise!

Did mine early summer - front to back and floor to roof
I can hear my pet spider walking on the carpet at 5000 revs

Now I have to open the windows to hear the whoosh

Fortunately the previous owner stuck himself together on mine

Why do you have a remote control on the C pillar??

It's not a remote control, it's a high power LED lamp.

That's the "mood setting remote" for when the ladies are a little tied up in the back seats with their feet in the stirrups. It dims the interior lighting, puts Lionel Richie in the CD player and turns the for way flashers on to let other doggers know that it's going down in your motor. Standard equipment in 20vt.

I disagree with the Lionel Richie cd

You went with something a little faster, something by The Prodigy perhaps?

T loves Smack my bit*h up...

How much weight is this adding Nigel?

I think the roof is quite an important panel to sound proof, you get quite a lot of drumming from it as it's such a large tin panel.

Yes, only you don't do it to me, as you know you'll get it back worse

I reckon about 2 - 3kg - the foam is very light

I'm still undecided about doing the roof - it already has a thick insulating layer (the headlining) so I think the biggest gain would come from adding some weight to the panel to prevent resonance. Having said that, it's not a flat panel, so it may not resonate at all

The roof does need some deadening, just ping the top of it.

I guess it's not so bad if you've got a sun roof?

So am I to understand this is why Nigel is installing sound-deadening, colour-coordinated to boot ?[oops sorry, unintentional]
Personally I make do with my recently-installed fade -in, fade-out rear courtesy light. Bit of a faff opening and closing the doors every few seconds, have to admit

Nigel, what do you cut this stuff with, as the blade must get clogged up?

Yes, the blades get a bit sticky, so I bought a set of eight cheapy disposable knives from the £1 shop while I was in Birmingham today.

Sadly, I left them at Motormech...

I'm going to try a little WD40 on the blade to see if that makes a difference

In general terms, light soundproofing doesn't exist... you have two issues: high frequency and low frequencies.

The first requires sealing of all spaces between where the noise is, and where you are, as well as removing resonances and things that can clink and clank at you. In particular, as most HF noise is white noise from the wind, pay attention to the door and window seals and make sure they actually seal.

The second is *much* harder to deal with, as it's carried through the solid structure of the car. You can't block it, but you can try and prevent it being so emphatic by the addition of anti-resonance panels in the large sheet areas: roof, bonnet, doors, and floor-pans. Bad news for performance; they need to be as heavy as possible, and ideally they need to be as 'floppy' as possible; if they're rigid, they will introduce their own resonances. (Soundproof doors in professional studios are solid wood with mobile airtight seals and filled with several hundred kilos of lead shot).

Fiberglass and foam (and eggboxes) do absolutely nothing to reduce ambient sound; their use is to remove room resonances by breaking up reflections and in some cases (perforated boxes of specified size and hole size) to tune the decay time of the room.

Oh you're soooo wrong... Have you actually tried?!

These are my rear quarter panels:

http://sfk.ibk.se/forum/attachment.php?s=41d74de3a87429eae66988810a61bcee&postid=82612

.. and they weight about 0.5kg more than std. The car is a LOT quieter.

What I wouldn't do is to attach foam to outer panels, that's a nice recepie for rust. There's a reason Fiat only put resonance-killers there.

Yeah, you've added floppy mass.

My view of soundproofing may not be as other people's - I design radio studios...

Some differences of opinion here....

I should be finished tomorrow, and the car can go back together and be tested - this will be the acid test of whether my £60 worth of sticky-back closed-cell foam was money well spent, or a severe case of snake-oil

I'm with Barnacle on this as the idea is to 'absorb or dampen' the energy, which the foambased product won't do comparatively when compared to the traditional sound deadening products. Whilst the foam is cheap and will remove some of the 'noise', it simply won't 'dampen' the sounds you are trying to combat

Jamie

Totally agree that asphaltplates stops resonance and vibrations while adhesive foam sheets stops actual noice/soundwaves. Hence the thinner heavy plates on body panels, and foam on plastic interior panels.

I think I have to agree with the professional on this one!

I'd just like to say that spending three days stripping the car, fitting the foam soundproofing and re-fitting all the interior was time and money well spent.

I'd LIKE to say that, but I can't....

It HAS made a difference, but not enough to be noticeable by anyone other than me. The general sound inside the car is now a little bit muffled and it feels as though every bolt has been tightened up to stop stuff rattling and squeaking

However, it's now obvious that the majority of noise in my car is transmitted into the shell via a mechanical connection. For example, the uprated engine mounts are making it noisier. The polybushed front wishbones are transferring road noise into the chassis. I'm also still getting quite a lot of the exhaust boom, which I had hoped would be removed by the copious amounts of foam in the boot. Perhaps I need softer exhaust hangers, or maybe just a different exhaust.

It was worth a try, but to be quite honest (and to support Neil's comments above) I recall getting a greater gain when I covered the inside of my Sprinty with B&Q lead flashing

Never mind - I'll just chalk it down to experience and hope that others learn from my mistake.

End of the day it's a bit of bonding with your motor Nige!

The traditional route to quietening a car is to pay attention to the bits where the suspension (and engine) joins on to the body. If those bushes are good and stiff, the handling will be good but the noise will transmit; if they're soft then the noise coupling is vastly reduced but so is the suspension torque coupling.

Damn.

What you need are bushes with low compliance at very low frequencies but high compliance further up the frequency range. Best of course, not to make noise in the first place... quiet tyres, attention to intake and exhaust systems, ensure that things which are whirling around aren't doing it in air or oil. You're onto a loser before you start.

It's clearly the level of mods that's made it noisy - a standard 20vt is like a Bentley in comparison with mine

Never mind - it's probably helped to make up my mind about buying a Punto diesel for the daily commute

Neil, I had planned on treating the insides of the external panels with Tetraseal Shutz, a bitumen based covering as an alternative to the usual cavity wax treatments, hoping to gain some sound dampening out of it as well.

Is that a forlorn hope?

My prime concern is to keep up the anti-corrosion protection which I renew every couple of years, sound reduction would be a bonus.

If you're adding mass to a panel, particularly non-resonant mass as Tetraseal, you'll get some benefit from both reduced resonance and reduced transmitted sound - but most of the noise in a car comes either through poor sealing or the bodywork itself.