Acoustic insulation / thermal

[Outbacknomad]

I have a pretty quiet car. But Australia's outback corrugated roads grind you down. Also AT tyres are a lot more noisy than road tyres.

I have used products from a few manufacturers, basically what was easiest to get. Money was not an issue as my time was worth far more than the materials.

Firstly get some panel trim removing tools, you do not need them often but they are very handy at times. A roller for butyl acoustic insulation. Buy spare trim panel clips. Some panels on my car they break every time you remove the panel.

Save some big pieces of backing sheet, comes in handy to double up to push foam into difficult areas & then peel back.

See if you can download a workshop manual for your car, very handy at times, especially getting into the dashboard.

Start with a small area, ie, a door panel. Once you have done 2 or so doors you will be more confident doing larger areas.

All up I have spent about 3 weeks of actual work but over about a year. I just kept doing more and more, mostly just to see how far I could reduce noise.

The floor on my car is extremely well insulated so the few things I did there didn't do a lot to reduce noise further.

The ceiling I only used 10mm foam originally and no butyl, but later added another 25mm thick engine bay foam. I was very surprised how much this deadened the car. Up to 45mm thickness in places simply to fill the ceiling cavity.

Doors, I started with 10mm but later stuffed them full of foam, this is a lot better, especially from the tyre noise in my case.

I have done the fire wall both sides, some really thick blocks where I could, this worked well. Lined the bonnet with expensive liner, actually 2 lots and butyl on the metal spaces of the bonnet panel.

Rear third of ceiling, later added another 25mm, there is another 10mm on the ceiling lining.

Easier to line door trim panel. Later I filled as much of the volume as possible.

Butyl and foam to quieten down mirror motors.

Filled the back of A, B, C & D column trim panels.

Column A trim panel, carful to split the foam across the airbag trim split line.

A 50mm thick block on the firewall. Steering column in foreground.

Further 25mm engine bay foam added to ceiling. This surprised me how much it decades the car. But it is the biggest panel. Up to 45mm thick in places so an acoustic "base trap". Also polyester ceiling batts, but thinner, for thermal insulation.

The car has sort of 2 firewalls, so filled everywhere I could.

Tailgate trim panel, easier to line the trim panel. Also stuck foam in the window surrounds.

Door window trim surrounds, a bit of foam in there.

I also have some old pyramid foam which I stuffed into tight spaces as it was more flexible.

Don't go overboard with butyl. I used 2 boxes, that was enough, but used stacks of foam, vastly more than I first used. I got a bit of 3 & 6mm foam which was useful in thin places. If I had the 25mm foam earlier I would have used that a bit more instead of layering up 10mm foam.

Used some mass load vinyl under the floor mats, in my car due to the good floor insulation probably not really worthwhile.

At the end of the day, a bit of butyl, but foam, foam, foam & foam as thick as you can.

 

[Nigel]

It is always most effective to block the sound as close to the source as possible, for example the most effective way to reduce tyre noise is to line the back of the wheel arch liners with butyl, or if you don't have liners then line the wheel arches themselves.

Column A trim panel, carful to split the foam across the airbag trim split line.

Unlikely to make much difference, however filling any voids, mainly to avoid resonances, with a small amount of polyester insulation material, the sort of stuff you find in pillows/quilts and some roof insulation, can make a significant difference.

 

[knapp7]

Good job!

Well placed assortment of sound deadening, sound blocking and absorbing absorbing materials.

I wasn't nearly as thorough as you were, but after doing my last vehicle, the wife said ... "Now that you've taken car of the road noise, can you do something about the road bumps?"

 

[Nigel]

can you do something about the road bumps?

High profile tyres are far more comfortable

 

[kamkar]

I just loathe what i call EURO boy racer tires, so thats low profile tired and big diameter rims, i have lost count on how many nice American cars that have been renovated / modified and then raped with wheels like that.
A mans wheel must be at the very least 70 mm tall.

 

[Dashmellow]

I've been driving with AT/M&S tires on my trucks for many years. None of them are quiet but some brands/designs are much quieter than others and some offer a good balance between road noise and performance when you operate your vehicle in multiple environments.

 

[Nigel]

I just loathe what i call EURO boy racer tires, so thats low profile tired and big diameter rims, i have lost count on how many nice American cars that have been renovated / modified and then raped with wheels like that.
A mans wheel must be at the very least 70 mm tall.

I've always said that if low profile tyres worked better then they would be used by Formula 1 cars instead of the 13" very high profile ones they do use, but even F1 is about to give in to the advertising and move to low profile for next year!

 

[jokiin]

It is always most effective to block the sound as close to the source as possible, for example the most effective way to reduce tyre noise is to line the back of the wheel arch liners with butyl, or if you don't have liners then line the wheel arches themselves.

Tesla take it a step closer to the source, they add insulation inside the tyres

 

[SawMaster]

On 'flat' pavement (none is actually 'flat' but is at least slightly crowned) a low-profile tire can have much better grip. But add in the real world where some roads are heavily 'crowned', and where you might find some of dirt and gravel, a higher-profile will grip better because it's more compliant to surface changes. It's also less likely to see damage from potholes and curbs. I LMAO when I see a new 4WD pickup equipped with low-profile tires and off-road tread design but it's all the rage here among the rednecks.

Phil

 

[Nigel]

Tesla take it a step closer to the source, they add insulation inside the tyres

And my Dunlop tyres take it even closer to the source by removing most of the tread pattern that runs across the tyre, leaving only the grooves that run around the tire, so most of the noise is not generated to start with! Surprisingly they have excellent grip in the wet, leaving me puzzled over why most tyres have grooves in other directions.

On 'flat' pavement (none is actually 'flat' but is at least slightly crowned) a low-profile tire can have much better grip. But add in the real world where some roads are heavily 'crowned', and where you might find some of dirt and gravel, a higher-profile will grip better because it's more compliant to surface changes. It's also less likely to see damage from potholes and curbs. I LMAO when I see a new 4WD pickup equipped with low-profile tires and off-road tread design but it's all the rage here among the rednecks.

Phil

I don't think low profile tyres do give better grip, if you go to extremes with drag racers, they have extreme grip and extreme high profile!

What low profile tyres do give is less flex in the sidewalls, so faster and more predictable response to steering input. I suspect that is a major reason that we see so many more videos of people losing control and spinning from USA than from Europe.

 

[Outbacknomad]

For most of us city roads lean more towards a goat track than a race track. Personally I want a comfortable ride. My car's data which I have long being putting into a spreadsheet shows average city speed of 32kph. Not exactly a race track! Probably a good thing that it's this slow due the numerous broken road surfaces.

Over a year or so I have tested the acoustic insulation by driving over some convenient set of catseyes and fairly poor road surface which are now very hard to hear. Broken surfaces, speed taming devices, bumps, potholes, and in the country cattle grids, are all a lot quieter.

Different road textures have varying degrees of noise reduction, but they have all improved. Even concrete roads are better.

Australia's outback corrugated roads are a reasonable degree quieter. It's a bit hard to explain it, but the irritation of the noise is substantially reduced.

The car is a lot quieter from outside noise, cars passing, noisy engines and exhaust. A much nicer place to be.

 

[Nigel]

The car is a lot quieter from outside noise, cars passing, noisy engines and exhaust. A much nicer place to be

And it can be a lot less tiring on long journeys.

 

[Outbacknomad]

Sydney - Darwin - Perth - Sydney, 4000km per leg shortest route. Agree, having a quieter car just simply makes everything more pleasurable.

When I replace the car acoustic insulation will be the very first thing I do. Worth every cent. Personally I could not give a stuff about bling on a car. None of this insulation you will ever see.


I made the mistake of starting at the rear of the car and the noise reduction was amazing, even though it was a quiet car.

The problem then that the the noise of the car seemed out of balance. It was to a degree why I then started stuffing the front with insulation.

Car manufacturers have actually gone to a lot of effort to reduce sound, but also to give a car a particular type of sound. Premium models often have more acoustic insulation.

So when stuffing the car with foam, think carefully about balancing the sound around the car as a whole.

Boot panels and amplifier pulled out, then added butyl and foam.

The foot well, in my car due to the already very good insulation, probably not really needed. But it can be very hard to notice the improvement in any one area at a time, but it is the overall total insulation around the car that is noticeable.

C column trim panel. I have tried to also get as much insulation up around ear level.

Boot trim panel clips on my car break and have to be replaced very time I remove this panel. (The blue air hose it for 3 onboard air compressors I have in the car for tyres and cleaning) The is more foam since taking this photo.

I pulled out air vents and lined the outlets to quieten ventilation. Also lined the hole this piece fits into.

Stuffed a bit of foam in the small hole running the length at the top edge of the door trim panels.

A lot of foam added behind all parts of the dashboard and glovebox.

I had already lined the door pockets with carpet, but then added acoustic foam to the back of the carpet. The foam is a bit thin but why not!

I also added aluminium engine bay firewall liner as aluminium has a different frequency response to deadening sound.

Replaced all the trim panel clips with one with rubber gasket version to help reduce noise transmission.

 

[Outbacknomad]

Thanks for comments. I hope it give a little bit of a heads up at what is possible.

Maybe the photos are getting a bit tedious, but when you get going on this and have the time it turns into a project to see how far you can push it. Keeps me off the streets so to speak!

Bonnet lining removed, sitting on engine.

First filled with butyl (bottom left corner), then expensive engine bay acoustic matting. The gas struts were ok with the extra weight.

Then a second layer of engine bay acoustic matting (expensive stuff, with hindsight foam would be fine). Once the original lining is back you can't see the additional insulation.

Some workshop manual images of some of the acoustic insulation in my car.



Insulation around the battery, have since added 25mm foam. There were a few other places around the engine bay where I have stuck a few pieces of 25mm foam.

One of the speaker trim panels on the dashboard.

I haven't gone overboard like this person with butyl who has the same car as me, a slightly earlier model, but in principle the same car. I have stuffed pyramid foam in the cross beams as they were completely hollow, two beams each side (the rear existing foam insulation is that thick that I could stick a 26Ah battery under the floor each side, I have been thinking about it, a project in itself!). I have put foam in the central console above the transmission tunnel. Also under the rear seat at the outside edges there was a reasonable size hollow space which I filled, that seems to help a bit. The B column I could stuff foam in there and keep it easily clear of the seatbelt mechanism.

The ceiling first has 10mm then the 25mm. In the hollow section above the door frames (black looking holes) I stuffed in pyramid foam. (Side airbag running the length of the photo, so insulation is clear of them)


P.S. To lighten up the mood!? Wifey can clean the car with our 3 air compressors which can also be used with water at 0.5L/min for OCD cleaning in the outback, or pump up each tyre from 20psi to 35psi in 30 seconds after being on corrugated roads.

 

[DT MI]

...The gas struts were ok with the extra weight.

Do you have any idea of the total weight you've added to the vehicle since you started this project?

 

[Outbacknomad]

Butyl 2.2mm thick 3.2kg/m². Used 2 boxes so 11.6kg in total.

12mm foam 0.55kg/m². Used 6 sheets so 6kg in total.

6mm & 3mm a sheet each, say 1kg.

25mm 2 sheets, say 4kg.

1.5m² of mass loaded vinyl, 6kg.

Engine bay matting, say 4kg.

Pyramid foam, say about 3kg.

So about 35kg all up.

I have put some boat carpet in the boot, so another 2kg roughly.



Weight is an issue for us as we are at our payload limit when we travel. A second spare wheel for the outback is another 30kg. Additional fuel, water, auxiliary batteries, air compressors, solar panels, fridge, tools, tow ropes, sand tracks, it all adds up frighteningly quickly.

 

[Nigel]

Do you have any idea of the total weight you've added to the vehicle since you started this project?

Unfortunately, when it comes to blocking noise, it is mass that does most of the work, much harder to reduce noise through absorption.

When I did mine, I actually reduced the weight, starting with a 20Kg reduction in the weight of the tyres and wheels, and being rotational mass that counts nearly double, something like 34Kg equivalent for acceleration/deceleration!

 

[Outbacknomad]

I agree that mass is the key the noise reduction.

Car manufacturers use the spare wheel in the boot clamped down against the body to help deaden that area.

I have spent over a year adding more and more insulation. Pulled the car apart too many times.

I do believe I have used too much butyl in my car. Probably like a lot of people have done, I have the car apart, and I don't want to do it again, so I will stick a bit more in than is really needed.

In my car probably 1 box of butyl (1.8m²) was probably not just quite enough, but 2 boxes was too much. I did put too much in the boot. In the front footwells it probably didn't do a lot as my car was already well insulated.

The mass loaded vinyl which I used on top of the front footwell carput, I don't think did much either. So that adds up to a fair bit of mass which the acoustic gains were very minimal.

I have stuffed every conceivable place with foam. Over repeated times pulling the car apart adding more and more.

It does reduce noise the more of it you have. But due to the foam being light it is reducing the higher frequency noise which is I believe the more irritating noise than low frequency noise.

When I filled up door trim panels, boot and thick blocks on the fire wall, I really noticed the middle frequency volume reducing.

This was very noticeable in the ceiling which has 35 to 45mm of foam.

Many years ago I was running a lot of computers from home. I replaced all the fans with quiet fans. It made a big difference. I also bought a pile of pyramid foam which I stuck around the room on the walls at ear level when working in the room. This was amazing, it decades the rooms sound, almost a bit too dead. (Put this in the car as most of the computers have gone)

A decade later in the car I have tried to apply these observations into the car. It's why I have added foam at ear level, above the head, in the dashboard and door window frame trims.

The result is the higher and medium frequencies have been made dead. A bit like putting a sock in a teenagers mouth so to speak. Everything is muffled, much easier to cope with!

The low frequencies are harder to do much about, but they are simply not as annoying to start with. But if the total volume of foam in the car is enough it will reduce the base noise a bit. A bit like a home theatre Base Trap. A cheap version is an unopened pack of ceiling batts sitting in each corner of the room, an unopened pack of batts is about the right density. The thicker the foam you can fill behind panels the lower the frequency it will have an affect upon.

So high frequencies are really under control. Middle frequencies well managed. Lower middle frequencies some sort of control which is good enough. Low frequencies not a great much done but a touch nevertheless.

But probably the better description of the overall noise reduction would be, less irritating noise. Which at the end of the day is what you really are trying to achieve.

The other benefit of all this foam in the car, is thermal insulation both summer and winter. I was surprised how much slower the car heats up and cools down. So a bit less of a load on the car's air conditioning in summer. A good thing in very hot places.

We in general sleep in the car, too lazy to put up the tent, we do not get any more condensation on trim panels. Together with all the windows covered the car is much warmer in the morning. We do actually get some ice on the car in the morning in Australia!

Windscreen sunscreens cut down to size for every window.

 

[jokiin]

I agree that mass is the key the noise reduction.

Car manufacturers use the spare wheel in the boot clamped down against the body to help deaden that area.

mass stops resonance which is the problem for larger panels, that's where you need the heavy stuff, the foam doesn't add a lot of weight but also serves a different purpose, for stopping rattles it's great too

 

[Outbacknomad]

What I noticed it that there are not that many large flat resonating areas of panels in the car. My roof has folds running the length, so it really isn't going to gain much adding an excess of butyl.

A different type of sound but nevertheless it is effective. Our neighbours installed air conditioning and two layers of steel sheet was added. The outside was roofing sheet and the inner sheet was perforated steel sheet. No batts or other insulation except the frame for the structure was timber. We can barely hear the air conditioning compressors now. Used correctly steel works. But obviously in a car one is stuck with the steel the car has.

Very carefully listen to the type of sound you are trying to control and focus on the really annoying aspects and manage that sound.