Those are bitumen strips that people use to patch zinc roofs. One side is bitumen and the other side is aluminium and about 3-4mm thick. You can find them in most hardware stores. The bitumen is sticky so all you need is to take the strip with the bitumen side facing the inside of the door/chassis and paste on.

Here is a simple NVH improvement that most people don't even think about. If you have the opportunity to remove the carpet, then do the whole flooring. If you don't want to remove carpet, one simple and cheap but effective noise reduction is to cut a piece of thick 9mm Insulflex the same size/shape of your car mat and stick it at the bottom of the mat. If you are doing the driver side, just make sure you have enough clearance between the mat and your accelerator pedal since the 9mm adds quite a bulk to the mat.

It reduces so much vibration from the floor that the car gives you a much quieter 'feel'.

The roof does not help much except when it rains. Also taking out the roof panel is a big pain in the butt. Do it wrong and you crease the roof panel for life.

The current topic on soundproofing reminds me of my soundproofing obsession 10 years ago. I also remembered buying insulflex in bluk, 3 feet by 30 feet and shared between my friend and I.