I think its important to talk about mass loaded vinyl too which is used to block and absorb sound waves.

Dynomat on the middle of panels that resonate to deaden them. Limp mass vinyl (can order at Home Depot, Amazon, Ebay, etc) sheets on doors, floor, etc. to block and absorb sound waves. And closed cell foam or jute insulation in cavities to absorb sound waves. LMV and insulation absorb the sound waves and convert them to heat.