How drywall blocks sound
STC (Sound Transmission Class) rises with mass, damping, and decoupling. A single 1/2 inch wall might rate STC 33–38 — normal speech transfers. Adding mass (5/8 inch or double layer), damping compound between layers, or resilient channel decoupling improves results more than “soundproof” marketing alone.
Specialty boards ( laminated viscoelastic gypsum ) add damping in one product — effective but pricey. DIY often doubles 5/8 inch with Green Glue or similar between layers on one side of the wall.
Practical upgrades for bedrooms and offices
Minimum meaningful upgrade: 5/8 inch Type X or standard on both sides, insulated cavity, caulk perimeter gaps, and airtight outlets. Better: staggered studs or resilient channel with double drywall on one side.
Ceilings need treatment too — sound flanks over plates and through joist bays. One heavy ceiling layer plus insulation helps home theaters under bedrooms.
- Insulate cavity — big STC gain for little cost
- Seal electrical boxes and plate gaps with acoustic caulk
- Double 5/8 with damping compound on one side
- Solid core door and weatherstrip — weak link if wall is heavy
Ordering extra material for double layers
Double-layer sound walls double gypsum on at least one side — multiply that side’s sheet count by two plus 10% waste. Damping tubes cover roughly 16 sq ft per tube depending on product — budget two tubes per 4×8 sheet pair.
Run base sheet math in our drywall calculator, then duplicate one-side sheets for the second layer. See 5/8 vs 1/2 guide for weight and screw length changes.