[klodolph]

Soundproofing an apartment is a pain in the ass. Are you thinking about acoustic treatment instead? Decent acoustic treatment can be done by putting absorbers, bass traps, diffusers in the room. Soundproofing is much more involved.

[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.