Casual noise can be reduced to a very tolerable level by simply “beefing up” existing walls, floors and ceilings. However, if you want to achieve significant sound isolation then a dedicated room construction is in order.
This construction is seen most commonly when there is a great deal of noise to be contained within the room, or contained outside the room.
Common Room Examples:
For this high level of isolation you will want a room within a room. All 4 Elements of Soundproofing should be deployed. Decoupling, Mass, Absorption and Damping,
The first element is decoupling. Keep in mind that sound is nothing more than a vibration. The vibration will travel (conduct) easily if there is a nice solid direct pathway to follow, like the string between two orange juice cans. If we cut the string, however, we “decouple” the pathway, and the sound vibration stops (no conduction).
Air cavities will resonate. Ever “heard the ocean” in a seashell? Ever blow across the top of a bottle and heard the sound? Both sounds are actually the trapped air resonating. A hollow wall will also trap air that will resonate. When the wall is vibrated by sound (from your neighbor), the air in the wall cavity is also vibrated, just like a drum. This air cavity is another means for sound vibration to travel from one side of the wall to the other
A very important element. In this case we simply mean make the walls as heavy as you can. Common cost effective choices for heavy materials include Drywall, Plywood, OSB, and Cement Board. For sound to conduct through a wall, it has to actually move the wall ever so slightly . A heavy wall is harder to move than a lighter wall. Simple as that. Drywall is one of the lowest cost sources of mass available. Best to use two layers of 5/8″ drywall. It is very important to note that a heavy wall will still vibrate, just not as easily
The last element for soundproofing. If we could reduce the drywall from vibrating in the first place, it would make the jobs of the mass, the insulation and the decoupling easier and much more effective. After all standard drywall is a HUGE surface area that is vibrating.
This solution finally addresses the noise vibration right at its source by applying mass and damping to the underside of the problematic, ceiling, walls and subfloor. Because this method directly addresses the vibration, there will be much less sound available to travel to the joists as well as your walls and floors. ..