Team-BHP - Hyundai Accent - rattle problem!!

Hi,

I own a Hyundai Accent, and was happy with that until last month. My friends used to say that my car's cabin is silent and is very refined. Since I live close by the beach, I was a bit worried about my car's underbody getting rusted..and so, gave it for 3M underbody treatment (also covers door pad and bonnet coating!) last month at a famous Hyundai authorized service center near my house.

I've no idea what they did, but no sooner did I take delivery of my car than I started getting weird noises inside the 'so-far' silent cabin. I took my car to the dealer again and asked them to fix those noises...they test drove my car to pin point the noise sources, and later said that there is some problem with the door panels. They insulated the door panels with thermocol (shud we use thermocol!?! sounds strange to me though!) and again test drove the car only to find that the noises haven't reduced much. Again, after a couple of test drives (wasted 2 liters of petrol!) they said the noise is from the rear speaker tray where I've installed (when I took delivery of my car, went straight to fix the ICE!) Pioneer oval speakers on a wooden padding. They asked me to leave the car for a day so that they can thoroughly check the noise creating thing. Even after leaving my car with them they weren't able to fix the noise problem.

It's highly irritating to see the inside of my car rattle on the slightest unevenness on the road or car vibration. Can someone here please throw some light on this strange problem?

Thanks in advance!

--giga