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Cheap sound insulation

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Old Dec 5th, 2011, 23:11   #1
Khe Sanh
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Default Cheap sound insulation

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.
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Old Dec 6th, 2011, 14:52   #2
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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.
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Old Dec 6th, 2011, 15:26   #3
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Thanks. I agree about the felt. Itís 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.
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Old Dec 8th, 2011, 10:37   #4
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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
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Old Dec 10th, 2011, 09:14   #5
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Update from Mitch:

Iíve 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 itís density also makes it better than anything Iíve 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 havenít 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/m≤ and 2kg/m≤ 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, Automobiltrimís 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 Iíve 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/m≤ whereas many other bitumen based products are between 1kg/m≤ and 2kg/m≤ 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 Automobiltrimís 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 didnít 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 Iím concerned with is added weight, to completely insulate everything will add quite a bit of weight so I still need to work out if Iím 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. Iíll 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
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Old Dec 25th, 2011, 14:48   #6
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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.
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Old Apr 28th, 2012, 11:40   #7
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From Bristol 603 (Nigel)...

I tried to add this to the articles thread on this topic, but I couldn't get it to work for me.


Dear All,

Inspired by Mitch's research, I decided I would undertake a sound proofing upgrade on my 122S. The sound proofing before the work was fairly normal and not in too bad a state, i.e. the bulkhead holes were all fitted with grommets, the gap around the steering column was filled by foam, bitumin sheets were stuck to some areas of the floor and transmission tunnel, the gear lever rubber was sound and filled with felt and there was some old felt under some parts of the rubber mats. The worst part of the existing sound proofing was the bulkhead under the dash where the felt was loose, thin and had holes in it.

Custom Audio Designs are in Petersfield, which is local to me, and so I sourced my materials from them as I could collect them in person which saved some time and delivery cost. The materials I used were:

FT 55 AL 5.5m x 1.2m roll - "Consists of a 10mm layer of acoustic absorbent felt bonded to our 5kg/m≤ T50 high performance acoustic membrane. Ideal for lining the inside of vehicles and bulkheads etc, can be used under carpets with the felt side downwards. Aluminium foil faced for extra performance and protection. Very pliable, high performance RW 25dB. Easy to cut and shape."


FR12SA Fire Retardent Acoustic Foam (self adhesive) 2 x 1.2m x 1m sheets - "This foam is totally non-flammable and is ideal for lining the bonnets of all vehicles. It is an excellent sound absorber and will protect other materials from a wide range of dangerous ignition sources. The material is black, soft, pliant, resilient and easy to fit.

SY50 (self adhesive) 6m x1.22m roll - "A polymer-based, asphalt-free, high density synthetic soundproofing membrane, that offers good acoustic insulation in different building elements. It has extremely high visco-elasticity as well as being extremely flexible even in cold temperatures. Another added advantage is that it does not contain any PVC."

I did a cheap and cheerful noise measurement before the work. Driving at 65mph down a flat stretch of local road using a sound meter app on my phone measured the noise level at 82db. I seriously would not trust this as an accurate/absolute measurement, but I believe it gives some sort relative measure for comparing with the measurements after fitting the sound proofing.

The first job I did was to fit a sound damping sheet (approx 50cm x 50cm) and then one of the foam sheets (1.2m x 1m) under the bonnet. This was quite easy with the bonnet taken off and upside down on the dining room table (wife and children out for the day!). I was glad of getting the self adhesive versions of these materials as they stuck strongly to the degreased surface and it was much quicker and less messy/smelly than using contact adhesive. Time will tell if they stay in place, but they do seem very firm at present.

I then repeated the noise measurement on the same stretch of road at the same speed. The result was 80db.

The second part of the work took much longer. I took out the seats, carpets, centre console etc and stripped off the now somewhat brittle bitumin sheets. The floors were sound, dry (despite plenty of driving in the rain) and rust free. I then added sound damping sheets covering about 25% of the area following Mitch's suggestion. The floors and tunnel were covered with the felt/absorber sheet as were the footwell sides (glued to the back of the front kick panels). I glued some felt/absorber over the sections of rear wheel arch that are beside the rear seat. I am unsure whether it is worthwhile, but I also put the felt/absorber under and behind the rear seat as these are big metal sheets and it seemed to me they might be a source of road/diff noise.

The upper part of the bulkhead was tricky as I didn't think the felt/absorber would stay in place here longterm even if glued, i.e. the felt would pull away from the heavier outer membrane. Instead I decided to use a sandwich of the foam and sound damping sheet. The self adhesive sound damping stuck strongly to the top surface of the foam. The sandwich would then be stuck to the bulkhead using the self adhesive backing of the foam. I used the shreds of the old bulkhead sound proofing as a template to get the rough shapes. It was then a case of lying on my back in the front footwells, trimming and easing the sandwich in to place. It took time, but fitted fine and seemed to stick strongly.

Removing the old rubber flooring had showed up some splits/tears in this and so I took the opportunity to patch it with some bits of old inner tube rubber stuck with contact adhesive to the rear. The seats and interior then went back in.

I really like the solid sound the Amazon doors make when shut. The bonnet was now shutting with a similar very solid sounding slam with the sound damping sheet in place. I decided to put a small section of the sound dampening sheet on the inside of the boot lid. This now shuts with a more solid sound. This is adding weight, but I think it must be only about 500g (Colin Chapman certainly would not approve and I am not sure if even I do!).

Driving the car down the same road at the same speed produced 78db. In a subjective way, the noise now seems less mechanical and the car is squeak and rattle free. It would have been interesting to have done a before and after spectral analysis, but sadly it is now too late to measure the before. My subjective impression is that a lot of the high frequency noise is gone, but I have no objective data to back this up.

In total I used about 4m of the felt/absorber and most of the two foam sheets. I think I used about half of the sound dampening sheet. The sound proofing on the bonnet was the biggest gain for the least effort. The rest of the work reduced the noise further, but took me about 10 hours (I am slow and not skilled). This was longer than I thought it would take me. I do a lot of motorway driving and so I hope the extra noise reduction will be worth the effort.

I hope this information is of use to others.

Best Wishes,

Nigel.
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