What are the best DIY ways to stop sound bleeding through a shared drywall wall?

The main problem you're hitting is a lack of mass and decoupling in that shared wall. Standard 1/2-inch drywall on both sides of a 2x4 stud bay is basially a drum head. If you want to stop that soundbar hum and the drawer slamming, you need density. Those acoustic curtains and foam panels are for room echoes; they won't do a thing for transmission through the wall. Adding a second layer of **5/8-inch drywall** using a dampening compound like Green Glue is your best bet without a full demo. It’s not technically a demo job since you’re just screwing into the existing studs, and it doesn't usually require a permit becasue you aren't touching the structure or electrical. And it’s a messy job, but it’s the most effective way to kill that TV bleed. But you have to make sure you seal the perimeter with acoustic caulk or the sound will just leak through the gaps. If you can’t deal with drywall dust, the floor-to-ceiling bookshelf idea actualy works, but only if you use actual books. You need the weight. If you leave gaps or just put knick-knacks up there, the sound will just wrap around. Lining the back of those shelves with **Mass Loaded Vinyl (MLV)** before you push them against the wall adds an extra layer of limp mass that helps alot with those low-frequency vibrations. Regarding the soundbar hum, that’s likely structural vibration traveling through the floor or the wall studs. If they have the soundbar sitting on a console that touches the wall, or worse, mounted to the wall, you’re going to hear it. Sometimes just getting a thick rug on your side or suggesting they put some rubber isolation feet under thier subwoofer can solve the low-end problem more effectively than any wall treatment.

Wait, if I add that extra layer of 5/8 drywall and the glue, what happens to the electrical outlets and light switches? Won't they be buried too deep in the wall to use? I'm a total novice with wiring, so I'm worried about having to move the actual boxes out or if there’s some kind of simple extender I can just pop in there. Also, does that Green Glue stuff have a wierd smell? I’m trying to do this in my bedroom and don't want to be huffing chemicals all night.

You'll definatly need box extenders—often called 'goof rings' at the hardware store. They’re super cheap and just screw into the existing box so your outlets sit flush with the new 5/8 layer. No actual rewiring needed.

As for the Green Glue, it has a faint vinegary smell while it’s wet, but it disappears once you seal and paint. One huge tip: pick up some acoustic putty pads for those electrical boxes. Most people forget that outlets are basicly direct holes into the neighbor's unit. Wrapping the back of the box with that putty stops sound from leaking thru the gaps around the wiring. It’s a game changer for those high-frequency voices.

One thing people miss is the baseboards. If you add that extra 5/8 sheet, you'll have to pull the trim off first or it's gonna look like a total mess. While the trim is off, check for gaps between the bottom of the wall and the floor. That's a massive sound leak. Stuff some backer rod or acoustic sealant in there before you screw the new layer up. It's wild how much noise sneaks thru that tiny crack right at the floor level.