About the insulations purpose... My Dad worked for Owens Corning Fiberglas research for 35-40 years (don't remember exactly anymore, but it was a long time). He was a chemical engineer and had about 40 patents to his name. I don't think he came up with the idea of putting the insulation on the hood, but I vaguely recall when he first did it and it was one of the first cars to do so. My recollection was that it was for heat, not sound reasons. Of course, my recollections sometimes aren't so good
But I am fairly certain that the original reason was for heat, not sound. Nowadays, maybe the purpose has changed.