Soundproof Walls

How soundproof is a six inch concrete enclosed wall?

I live in an apartment and I have a home theatre setup with 5.1 speakers. They're pretty big speakers and I would like to know how soundproof my apartment is? The concrete walls are approximately 6-8 inches thick and they fully enclose the apartment. When you knock on the walls, they do not make any reverberations, in fact it feels solid and your knuckles hurt if you knock hard enough. How sound proof is my apartment? How loud should I be able to play my movies/music?

Public Comments

1. Concrete transmits pretty well, especially low range. But really, the only way to know test it. Go to your neighbors and tell them you want to make sure they can't hear your stereo. They'll gladly let you know. You can have them call you and stay on the phone while you crank it up and have them tell you when it's too loud.
2. I agree with ElDub. Go and ask ur neighbors and see if they can hear it or if you want to be a jerk just turn it up and see if anyone calls the cops or knocks on your door to turn it down. Its your choice on what you want to do. If you want it sound proof you would have to buy the material to do that. That also gets expensive real fast.
3. Compliments on caring how your listening might impact your neighbours ... too many don't even consider this. Degree of soundproofing is difficult to define and varies widely depending on the particular structure of the room/building. Soundproofing is frequency dependent, with the most difficult thing to suppress being bass transmission. And the most effective way to prevent bass notes getting through to your neighbours is to increase the mass in the walls and ceiling, etc. Concrete is good, so the chances are that your music/movies won't be much of a bother to your neighbours, BUT you should test to find out since even small openings (e.g. for wiring or plumbing) can lead to significant sound transmission even in concrete buildings. I suggest, like others have done, that you talk to a neighbour on each side, and maybe above and below and discuss testing how loud you can get without them being bothered. Note that bass will still come through, and different people have different tolerances for sounds (and it can vary with time of day). My guess is you can play movies/music fairly loud, but at surprisingly low levels, bass will still be an issue. It might be advisable to mount your subwoofer on a rubber pad before testing. See the article at the link for general info on soundproofing. Hope this helps.
4. I had an apartment with a foot of concrete and the sound still carried enough to get complaints. But then again it also depends on your neighborhood and neighbors. Ghetto neighbors don't care, whereas snobby neighbors will come down on you hard