[kibwen]

Improved standards for thermal insulation (important for reducing energy consumption from heating and cooling) will have a side effect of improving the acoustic insulation of structures. Not quite to the same extent as dedicated acoustic insulation, but better than nothing.

[brickfaced]

Ditto fire safety. High-rise apartments where I live tend to have concrete floors and sturdy walls between units for this reason, and it helps greatly with noise reduction.

[phaserphile]

Yes, air tightness is part of the problem, but if that's the only tool used, sound is still going to get through. Double walls help dramatically.