This will help, same principle
HowStuffWorks "Insulation"
There is also insulation that stops skins drumming and producing noise as the aircraft shakes and vibrates, imagine a drum as you beat it, then put your hand on the drum, it kills the noise, that's what some thick materials do, they also have a thick type paint/ paste as well on light stuff that is painted on the inside of the skins, you could demo that with a drum or sheet of paper then stick a sheet of card on and show how it stiffens up and won't flex.
Some aircraft use white noise, the Saab 340 I think does, this is played in the cabin and is the opposite of the noise the engine and props make so cancels it out.