You need to be warned. Car modification is quite a contagious disease, and according to some folks, is a variant of enzyme. It can be incurable unless you have the ancedote, which I will talk about it in my next article.

Shortly after I have upgraded my 17″ MOMO wheel, the modification itch came back again, within 24 hours. The thoughts of sound damping and proofing my cabin so that I feel like I am driving a Lexus have been lingering around for a long while, and I just feel like as if floodgate has opened, and I just got to continue my modification plan.

Honestly speaking, our cars (Volkswagen BORA) are quite well sound proof'ed and dampen'ed when they came out from factory, at least for the non audiophiles. But it doesn't mean there's no further room for improvement, and I have decided to approach Express Motion Pte Ltd for their professional advise.

Basics
The terms sound proofing & sound damping are sometimes mis-understood as the same. Sound-proofing is a technique that makes use of sound-absorbing material to eliminate noise or keep as much noise as possible out of the cabin. Sound-damping on the otherhand, make use of visco-elastic material to reduce or eliminate noise as a result of vibration energy being disperse from a structural part of the vehicle, such as door panel or boot panel.

Different individuals, armed with each of their own sound proofing/damping objectives, will have different noise control requirements. Not being an audiophile, I do not need to damp all possible cabin body surface area when they might just yield minimal vibration energy. This, however, might be a big deal for audio enthusiast, so please check out your requirements and objectives before embarking on such project.

Scope of work .. sound proof + damping
My high level objective is er .. to transform my car cabin into a Lexus cabin. Obviously, you pay a peanuts, you get a monkey. (although I beg to differ on the fact that I am getting every penny that I have paid to the dealer), hence, unless I throw my money on a new Lexus car, I had set my expectation to a more practical level. I told the boss of Express motion that I just need a quieter cabin, and better audio environment, in that order of priority.

I was recommended to dampen my front wheel arch, sound proof my floorpan, and damper my front side doors. On the hindsight, I think I might get even better result if I had sound proof my wheel arch, instead of damping it.

The process was quite laborious, and elaborated. The merticulous workers had to removed all the seats (front and back), as well as the seat frames, so that the floor carpet can be unlaid. When they uncover the carpet, I observed that there's a moderately thick layer of sound absorber material beneath the carpet, and that's why I suggested that our cars are already sound proofed (at certain level) from the factory.
The material that the workers used to sound proof my floorpan is Accumat AMT250, which is 0.250″ thick noise control material used purely to reduce or eliminate noise. Unfortunately, at the time when I was doing my sound-proofing, my digital camera just ran out of battery, and I couldn't take any picture of the process.

As the workers proceed to work on the door sound damping, they have to slowly remove the door panel. I notice that one can actually DIY on the door sound damping easily, if you can comprehend the steps[/b] described by [url=http://forums.vwvortex.com/zerouser?cmd=viewprofile&id=49760]VgRt6. Soundproofing your floorpan will be alittle tricky, so I suggest you leave it to the professional unless you are a true DIY man. The material used for damping the door is the same as that for the wheel arch, which is Accumat AMT045 , very much thinner than the soundproofing material. It's evident that the material is not meant to fend off any noise, but reduce noise via reducing unnecessary vibration of the body parts. On by the way, as you are taking out the door panel, becareful when you pull out the panel from the door, the clips may snap and break if you do not pull out properly. It's better if you prepare yourself with spare clips, (P/N: 3B0 868 243) which cost less than $1 each.

The arrows point to the clips that are vulnerable for breakage

Wheel arch sound damping is also quite straight forward, you just need to turn the wheel so that you have access to the torx screws that secure the wheel arch cover. Once the cover is removed, it exposes the metal frame of the wheel arch body. We used the same damping material as we did for the door panel.

All in all, the work was nicely done up by Express Motion within 3 hours, considering that they have been careful in dismantling the parts and trims just to lay the damping or proofing material. The price is a friendship price, so it's non-disclosure. But you possibly can get it done at less than a grand, a full sound proofing/damping (including the boot and rear door/wheel arch) will probably set you back by $1400.

Other references
1. VgRt6's DIY guide on door removal
2. Express Emotion Pte Ltd @ Upper Thomson Road
3. Accumat product page