Cheap sound insulation

[Burdekin]

I've been doing quite a bit of research into what is the best sound insulation for my Amazon. Of course there is expensive stuff like dynamat but I reckon I can get as good if not better results and a lot cheaper. Big claim I know and maybe wishful thinking but I'll explain what I've learnt and a big thanks to Darren and the noise vibration guys at Tata. The first thing you want to do is add mass to large panels to stop them resonating, Volvo already did this on the floor but for improved results add it to all large flat areas like the doors etc and as a general rule you only need to cover 25% of the surface, the goal is not to block the noise with this, it's only there to add mass so the panel resonates at a much lower frequency. The sound deadening pads here http://www.automobiletrim.com/sound-proofing.htmlt cost £65 for 10 but if you already have the original sound deadening on the floor you won't need that much maybe only half but it's easy to work out, just measure and divide by 4 and that's all you need.

The next layer is an absorbent layer, absorbing sound in your car really isn't effective as you can't get the thickness required but this layer is very important to isolate the top layer. There are two materials I have found that will work well here depending on where you are putting it. There is the sound proofing felt here http://www.automobiletrim.com/sound-proofing.html that will work well on the floor and will be easy to lay and then there is Closed Cell Foam that will also work really well as the middle layer and would probably be better for areas like the doors but will work fine on the floor as well but will probably be a bit harder to lay. The foam doesn't need to be too thick as it's main purpose is to isolate the final layer, I would say 3 to 6mm will be plenty. I have found this cheap option and I think would be ideal: http://www.needlesports.com/Catalogu...ength-BEA-TULM

The final layer is the sound blocking layer and the best material I have found is Mass Loaded Vinyl but the original rubber matting probably will work okay as well here. When using closed cell foam as the middle layer I would bond it to the Mass Vinyl Layer. You also want to cover as much area as possible with the middle and top layers and you don't want gaps where you join the final barrier so overlap the seams and glue them together. I haven't found many places selling Mass Loaded Vinyl but I have found this website selling it at a very reasonable price http://www.domesticsoundproofing.co....barriermat.htm

So that's it. There's also things like blocking all holes in the bulkhead and the wheel arch protectors would probably help reduce road noise transmitted from the wheels.

[Quarterless]

Nice post!
In addition to this a negative on the felt matting is it acts like a spondge and is a big link to rust/holes in the floor pan. Therefore before fitting make sure your car is water tight.

[Burdekin]

Thanks. I agree about the felt. It’s also worth checking the original sound deadening material, if there are any high spots this will most likely be the floor rusting and should be removed. I have gone to a lot of effort over the last 6 weekends or so to waterproof my floor after I weld repaired a few holes in what looked like a nice floor with no issues.

[Gordon Hunter]

Thanks Mitch for a well researched and extremely helpful post.
Think I'll move this to the articles section.
If there are problems adding anything else relevant to this then do let me know and I'll edit it.

Gordon

[Gordon Hunter]

Update from Mitch:

I’ve ordered my insulation and there was a slight change of plan after I spoke to the guy at custom audio designs. They no longer do the Mass Loaded Vinyl (MLV) sheets but recommended their Tecsound insulation and he says it performs better than MLV. I also looked at the technical aspects and it’s density also makes it better than anything I’ve found so far as a sound deadening material to apply directly to large areas. The tecsound SY50 has an adhesive backing on one side and an aluminium foil facing on the other so sticking this to a panel will do the same job as Dynamat in that it dampens vibration. I haven’t been able to find out what the density of Dynamat is but the tecsound 50 range is 5kg/m2, bitumen based products are between 1kg/m² and 2kg/m² and this 3M product is 3kg/m2 http://3mcollision.com/media/documen...deningPads.pdf so effectively you need less to dampen the panels. A price comparison for the dampening material without carriage is: Dynamat £44/m2, Automobiltrim’s sound damping pads £31.2/m2, Tecsound SY50 £10.50/m2 and considering you need less of the Tecsound SY50-ALU it seems like the obvious choice. Info on the Tecsound SY50 that I’ve ordered for the panels:

Tecsound SY50-ALU is a polymer-based, bitumen-free, high density synthetic soundproofing membrane, that offers good acoustic insulation coupled with an oil resistant, reinforced, aluminium foil facing. It has extremely high visco-elasticity as well as being extremely flexible even in cold temperatures.
This damping material is unique. Unlike most other foil faced damping sheets which are bitumen based, Tecsound is not only Class0 fire rated but it tolerates extremes of temperature. It will not harden and crack when it gets cold thus reducing acoustic efficiency. It is also 5kg/m² whereas many other bitumen based products are between 1kg/m² and 2kg/m² and therfor not as effective at damping thicker metalwork over 0.25mm.

For the front floor section I will be using the Tecsound T50 over Automobiltrim’s felt as the absorbing and isolating layer and for the rear I will use T50 bonded to the closed cell matt. Another advantage of floating a sound barrier over the absorbing layer that I didn’t mention previously is that the felt or foam will absorb noise travelling into the car and then again as it bounces off the sound barrier layer so the sound barrier layer also increases the effectiveness of the absorbing layer when used in conjunction with a barrier. One area I’m concerned with is added weight, to completely insulate everything will add quite a bit of weight so I still need to work out if I’m prepared to compromise some extra cabin noise and not insulate 100% and concentrate on the worst sound transmission areas. I will add new damping material to all panels and remove all old material and Darren has recommended then only using Thinsultae between the door cards and the door bodies and says a lot of new cars use this as the insulation in the doors, it will be a compromise as without the barrier the Thinsulate will not be as effective but it is suppose to be quite a good absorber of sound.

The Amazon will have quite a bit of wind noise due to the gutters, quarter windows etc and this noise will be difficult to block. I still also need to see if some Thinsulate, foam or felt under the roof lining would help reduce some of the wind noise.

A120 Tecsound 50 6m x 1.22m (7.32m2) £48.60 + vat http://www.customaudiodesigns.co.uk/...c-membrane.htm

A130 Tecsound SY50 6m x 1.22m (7.32m2) A/Backed £63.43 + vat http://www.customaudiodesigns.co.uk/...c-membrane.htm

Due to the weight of the Tecsound carriage is expensive as it needs to be by pallet and it cost £55 for my order so you need to make 100% that you order enough in the first order otherwise you will be paying for delivery twice if you need to order more material. For a cost comparison Dynamat would have cost me an extra £600 to order the same area coverage from Ebay. I’ll give a run down on exact amounts of each material used and the prices when I insulate my estate to give folk a better guide to exact amounts so you only need to buy exactly what you need.

If possible I'd like to do some sound readings when done to try and quantify the improvements but unless my work has a meter I can use it probably won't happen.

Cheers,

Mitch

[Gordon Hunter]

From Colonel Froth....

I was going to say that if you have access to a smartphone you can take basic noise readings. There are applications which measure db readings over time like this and this and have varying levels of other features. None will be as good as the proper tooling mainly because they use the phone's microphone which is optimised for human vocal frequencies. (Although if playing.. uh.. experimenting with these devices is something that someone were keen on, android can read microphone data through the mini-jack headphone socket if the phone has the hardware.)

I thought it was worth mentioning despite the fact that many of us are as likely to have a smartphone as we are sound level meters.

I think a lot of people would be interested in seeing some comparative readings, I definitely would.