How do I achieve stc 55+ on existing wall + radiator problem

[Sensei_Rebel]

I wanted to soundproof one room with neighbors that are constantly yapping and I can hear them quite well. The stc rating is well below the standard on this wall. How can I achieve stc 55+ if I can't afford or aren't allowed to put up a new wall ? Plus I'd like to do it myself if possible.
 
Also my room has a radiator panel running on the bottom around most of the room. How can I soundproof a wall if the radiator is there? Can I just cover the radiator with mlv or other materials if I want to put soundproofing material on the wall its connected to ?

Thank you very much for any advice.

[johnbergstromslc]

Unfortunately, I doubt you'll get anywhere near STC 55 without adding new structure. 

[Sensei_Rebel]

I understand. So what kind of structure would be good? Since this is a co-op, I can add to the wall, although I don't think I can break down the wall and put insulation inside it. Would simply adding a new wall or resilient channel and the existing wall with 3 inches or more of dead space and sound insulation material inside it be good enough for what you're talking about?

And what about the radiator problem? Since I can't block it off with a new wall, could I put some mlv behind it instead to help with the added wall?

[johnbergstromslc]

Check with your co-op board before starting work.  It would be much better to tear off the existing drywall, insulate the wall before building the new wall (or converting the old). 

Follow this link to understand why:

http://www.greengluecompany.com/understandingTripleLeaf.php

If the radiator is electric baseboard, it's easy enough to remove and reinstall.  Hire an electrician if you don't feel confident to do it yourself.

Sorry, I know you were hoping for an 'easy' answer, but if you want decent, lasting results, there is some difficult work ahead.

[Sensei_Rebel]

Yes I read the triple leaf article before. I've been reading all I can find about soundproofing lately. What I was thinking of doing is adding a cement panel on the wall first, and then mlv with the Green Glue assembly combined over it. Would that not be good enough to block their conversation and door slamming I hear ? Just putting up my bed up over the wall blocked the sound pretty well.

Also this radiator I believe is installed around the entire length of everyone's apartment. I'm not sure if they'd let me do anything to it.

[johnbergstromslc]

Well, cement panels seem great for soundproofing, but they're really not wise.  Cement boards weigh about 100 lbs vs. 80-85 lbs for 5/8" drywall, so you get the beneficial additional mass.  But cement board costs $20 per sheet vs. $10 for drywall and is a major bitch to cut and install. Also, cement board is porous like cinder block or concrete, so you'll have to really slop on multiple layers of paint to get good performance.  Skip the headaches and keep it simple - stick with drywall.

The method you're thinking of using, sandwiching MLV with Green Glue, is probably not a good idea.  Green Glue is designed to adhere 2 panels of equal density, so they will vibrate in the same manner and induce a shearing force in the adhesive and dissipate some of the noise into heat.    Having MLV in there will just muck up the system. 

As I'm sure you know by now, the best solution would have a decoupled wall, with insulation and lots of mass on each side.  Having your wall panels rigidly connected to your neighbors (via the studs) is responsible for most of the noise you hear.  Since it sounds like you can't achieve this, just install an additional layer of 5/8" drywall with Green Glue.  I'm not sure what STC rating you will achieve - maybe it's shown on the Green Glue website.  It will certainly be better than what you have now.