I have an old car (FIAT Panda, 1993) which has basically no sound insulation. I like to work on the car to improve it, so I thought about sound insulation. I'm not looking to improve sound deadening of the interiors.
At this time I have almost all the info I need, but I would like to know which material is best suited to proper insulation.
Doors: they cannot be "opened" in two, the two sides are welded together, so I will put bitumen bands on the inside, the strips meant for roofs like http://www.bostik.nl/nl_NL/toepassingen-en-producten/zoek-op-segment/bouw/BatuBand/SCNL0206/producten-3/?detail=1 because Dynamat and similar are too expensive.
Hood and engine compartment: if there are exposed parts of chassis that resonate, bitumen strips, plus (according to ease of application and securing) rock wool.
Trunk: on the bottom below the floor covering, bitumen strips if needed and either rock wool or foamed laminate underlayment (http://www.bestlaminate.com/vapor-3-in-1-blue-underlayment-100-sq.ft-roll/). This underlayment is rated to >10 dB attenuation (I suppose for impact noise).
Inside the vehicle, floor: for sure laminate strips where the chassis resonates, plus either rock wool or foamed laminate underlayment below the soft plastic flooring.
My doubts are all about foamed underlayment vs rock wool.
What are the pros and cons of each alternative? keeping also in mind that I cannot easily find rock wool thinner than 30-60 mm (not under compression).
In the engine compartment rock wool is the only option due to temperature and environment, but below the internal flooring I'm unsure what to choose.