Using Green Glue to add a new layer of 5/8” drywall is still industry standard because it's a high performing, cost-effective solution to soundproofing a wall without removing the drywall that's already up.
The cheapest and most effective acoustic insulation is fiberglass insulation for walls, while acoustic foam panels are great for budget-friendly soundproofing. Both offer decent noise reduction at a low cost.
Blown-In Insulation: Blown-in insulation, such as cellulose insulation, can be added into existing walls to increase their sound absorption abilities. It fills the little nooks, crannies, and holes in the wall, trapping sound waves and reducing noise transmission (3).
The best thing you can do is get sound treatment with an air gap between the treatment and the wall that faces your neighbor. The cheapest solution here would be to get a large room divider curtain rod and a really thick, sound deadening room divider curtain.
Alternative Solution: Mass Loaded Vinyl + 5/8" Drywall
Mass loaded vinyl is a great soundproofing material because it is super dense, versatile, and great at blocking sound. Best of all, it checks the “varying materials” box.
Walls – Soundproofing wall may involve decoupling inner and outer layers of a wall, adding more mass between the walls with dense materials, or applying a damping compound. Sound absorbing the walls may involve adding acoustic panels, decorative fabrics, or wall coverings that absorb sound waves and reduce echo.
Investing your budget into the decoupling framework is a far more cost-effective way to soundproof your stud wall. The saving is made by only using a single layer of acoustic plasterboard over the top. This massively reduces your spending while also giving you excellent soundproofing.
This surprisingly high amount of sound leakage from such small holes and cracks can be readily treated and eliminated with the use of acoustical caulk. Latex-based acoustical caulking provides an effective sound barrier because it remains soft and pliable for its lifespan and will not harden and crack.
Several materials are effective for soundproof insulation, including fiberglass, mineral wool, cellulose, foam panels, and mass-loaded vinyl. The best material for your project depends on factors like your budget, the level of soundproofing needed, and the installation area.
The best affordable way to soundproof your walls effectively is to use drywall and other materials like acoustic caulk to create an air-tight wall space. Installed over insulation and sealed in to form an extra layer in your walls, drywall forms a solid barrier for sound.
The best, and most common, method for adding insulation without removing drywall is through the drill-and-fill method. Using the drill-and-fill method, the insulation is blown directly into a closed wall through small holes drilled into the wall.
You can use MLV between drywall layers to significantly reduce noise. Make sure to use acoustic caulk to plug gaps, leaks and cracks around doors, switches and anywhere else noise might be seeping through.
Soundproof paint is a specially formulated paint that contains sound-absorbing particles. Once it's applied to a surface, it creates a thin layer between the wall and whatever sound it's intended to absorb. That might sound like science fiction, but to the credit of the manufacturers, it does work how it's intended…
The purpose of the rubber in the sound isolation clip is to break up the sound that transfers from the plasterboard to the steel stud and through to the other side. Typically, a wall or ceiling would be constructed by installing a stud frame, finished with plasterboard.
Summing Up. It is not necessary to soundproof an entire wall to obtain good soundproofing. Laying soundproofing material over 15 to 30 percent of a room is sufficient to block noise.
Green Glue is a noise proofing compound that can be used in wall, floor, and ceiling assemblies. It acts as a decoupler to stop sound from passing through to other areas or rooms. It converts noise energy into heat, thus quieting down noise as it passes through it.
Seal the wall: Use an acoustical caulk to seal any vents or outlets and gaps around the wall's perimeter. Add drywall: Install new 5/8-inch-thick drywall using Green Glue between the layers. Reapply caulk: Seal everything using the same acoustical sealant.