[coldtea]

A room, not a whole apartment. From what I read it costs around $3000 to $5000 to have it done professionally in the US (and one can do it himself). You then add acoustic treatment (with commercial or home made items) which is considerably cheaper.

I assume though that you're not expecting Abbey Road level soundproofing, just home-studio level, enough to not annoy the neighbords when monitoring/mixing at a reasonable volume at 2am.

[klodolph]

Yes, a room in an apartment. It’s a pain in the ass. Yes, it’s a pain in the ass to soundproof a room to the point you’re not disturbing the upstairs or downstairs neighbors.

There are so many ways that your building will transmit sound from one apartment or room to another.