I have long wanted to investigate advanced methods of reducing noise transmission between rooms; it seems to me that's a area that will clearly need improvement if we really expect cities of the future to be towers and condos instead of standalone houses. But you're correct that whatever solution does exist won't look / act like noise-canceling headphones.
I think that's an area that would benefit less from investigating and more from acting. But for some reason people think a room that's 20cm wider is "better" than one with sound-proofed walls.
