For sound and heat resistance there is a padding out there that you install between the floor and the carpeting that is a foil backed insulation. Check with your local auto parts store.
Short answer, NO you do not NEED undercoating.
The undercoating color is determined by the manufacturer's choice and may not always be related to the exterior color of the car. The goal of the undercoating is typically to provide corrosion protection and sound insulation, rather than to be inconspicuous. Dark undercoating can sometimes provide a visual contrast to make it easier to inspect for any damage or corrosion.
It will depend on how much undercoating you are wanting to rubberize.
No.
starting at $150
according to the info i read on the back of my can of undercoating, it only takes 10 minutes. I'd give it a 1/2 hr myself.
No, undercoating should last for years.
Light,heat and sound are all energy.
Yes, sound waves can generate heat through a process called acoustic heating, where the energy of the sound waves is converted into heat energy.
Undercoating is a waterproof coating applied to cars' undersides to prevent them from rusting. The parts under your car are also vulnerable to damage from the elements (especially in north climates), oil, tar, and items that fly up from the road.
Sound doesn't travel in heat. It travels in a physical medium.
no