Ironically, you can make a better sound isolation barrier using modern building materials than you can with concrete. Mass-Air-Mass. Basically, with a normal “stick built” wall with two layers of sheetrock on both sides, you can get upwards of 60Db of reduction. Make it two decoupled walls (no sheetrock between, mind you), and you can get 80Db. That’s enough to play the drums without waking a baby in the next room.

Oh, and normal concrete walls are outright dangerous in an earthquake of any magnitude. They’re too stiff.