I'm trying to understand why all my efforts to soundproof a wall in our bedroom keep failing.
Here's the situation; Our north wall is 46ft long, 1 and half stories high (half the lower level is in the ground), no windows or doors. All our bedrooms and bathrooms run along the wall. Directly on the other side of this wall is our neighbors deck (about 5-6 feet away). When they're on the deck talking and yelling, we can hear them... all night
Originally, this wall had 5/8 drywall, 2x6 framing, fiberglass insulation, 1/2 osb, 1.5in Styrofoam, vinyl siding.
To start fixing this, I simply added a layer of 5/8 CertainTeed SilentFX drywall in our bedroom. The claim from them is that it "features a viscoelastic polymer between two specially formulated dense gypsum cores significantly improves sound attenuation and is ideal for systems requiring high STC performance." It was super heavy stuff. I installed it over the existing drywall with a gap all around the edges which I filled with acoustic sealant. This helped a little but we can still hear the neighbors talking and yelling.
I found out that the OSB on this wall had a lot of rot due to the Styrofoam not being sealed. My thought was that the rotten OSB (lack of mass), was letting a lot of noise through, like an open door. Also, it seemed to me that Styrofoam can amplify sound (I can share some youtube video's to show what I mean). I tore down the outside of this wall, replaced all the OSB, sealed all cracks and gaps, then replaced the Styrofoam with Rockwool Comfortboard 80 (suppose to absorb sound). After doing all this... there was NO change in the amount of noise coming in. I was totally shocked.
Am I cursed? Or is there something else I've missed? Based on the STC rating of the drywall alone, I shouldn't be able to hear anyone talking normally. Yelling should be murmurs.