Originally Posted by tigas
I used ½ Quiet Rock Drywall as recommended by the company on a wall between two apt. units. The QR drywall was installed by drywall installers per product instructions over the original wall. Which was drywall covered with ¼ plaster on wood 2x4 studs. The building was constructed in 1968. I can still hear people talking, and tv, on my side of the wall where the QR was installed. The sound has been reduced, but at $45.per sheet plus installation I am not happy with the results. Would blowing insulation into the wall cavity stop sound?
Blowing insulation in would have minimal effect, and may make things worse. You say the QR was installed 'as per instructions', but there is a lot of detail to cover, and unless your drywallers understood the issues involved and how to address them, you may still hear noise.
Your problem may
be 'flanking' noise. That is, noise that goes around the QR via unsealed openings. For instance, it may be traveling through the joist space on top of the wall, or perhaps acoustic sound sealant wasn't used around the perimiter of the QR, including at the floor, under the QR.
There are lots of ways noise can 'leak'. I've done extensive research on soundproofing for an in-process project. I thought about using QR, but decided on a staggered wall with 2 layers of 5/8" rock and GreenGlue, as it was a bit cheaper. I hear that QR is good, though, but it must be properly installed, which means addressing all ways that noise can enter (think of noise as water. If there are leaks, it will 'seep' through).
Here are some links I've saved. Really good info at both of these sites:
GG's technical library along with 2 very interesting articles (included in the 1st link as well):
Very informative here:
Read through these and other articles in the libraries before
you spend any more money on it. Be fully educated so that you know what needs to be done, how much it will cost and how it will perform.