One of the things I (probably incorrectly, but) happily spent money on over the last couple years was putting soundproof windows. I think having better sound i

One of the things I (probably incorrectly, but) happily spent money on over the last couple years was putting soundproof windows. I think having better sound isolation in apartments would make them substantially more liveable, and it's not comparatively expensive versus many other upgrades you can make to multi-family housing.