There are none.
The cheapest approach is to give whomever you're worried about disturbing $30 for movie tickets and popcorn.
I don't mean to sound flip, but soundproofing cannot be even partially achieved without significant structural modifications. That means adding mass to walls in the form of extra layers of sheetrock, reinforcing doors and windows, making sure everything is tightly sealed. I won't even get into issues involving shared HVAC ductwork.
Don't mean to bum you out, but I advise against anything quick and dirty, unless it's so quick and dirty it won't piss you off to find it didn't work.