noreasters t1_irbqfo3 wrote on October 6, 2022 at 8:22 PM

Add a second layer of 1/4” drywall (with caulk or sound dampening epoxy on top of old drywall).

Mass slows sound wave propagation and drywall is more dense than insulation, adding the material between old and new drywall forces sound waves to energize both boards with little direct transfer of that energy…highly effective.

elemenohpee t1_irclroc wrote on October 7, 2022 at 12:36 AM

Why only 1/4"? You're trying to add mass to the wall, so wouldn't 5/8" be more effective?

noreasters t1_ircm7mt wrote on October 7, 2022 at 12:40 AM

The real deadening is in the slowing of the sound waves.

Sound waves must vibrate the material to pass through.

2 layers of drywall with flexible material between means sound wave must vibrate outside panel with inside panel resisting and the filler material acting as a spring damper…BEFORE the sound can begin to vibrate the second board, now fighting the motion of the first.

After the sound passes that material it will have MUCH less power and ability to travel distance or vibrate other walls.

Edit: this means 1/4” drywall, or most any hard material, can be used; 1/4” drywall is cheap and relatively easy to work with.