Hearing your neighbour's noise through your walls? Mad at the builder for not building soundproof walls? Sorry but it's probably not the builders fault at all. If you're going to solve your noise problems coming through the walls, you'll need to understand the problem in detail.
Ideally, when trying to reduce sound it is very advantageous to apply the soundproofing materials on the noise-producing side of the wall. However, if your neighbor is the noisy one, this would mean applying the soundproofing to his side, and generally noisy neighbors have no interest in helping. So you'll have to treat your side.
One very important thing to keep in mind is the noise from your neighbor isn't only pouring through your wall. Some amount of sound is flanking around that wall and also entering through the floor and ceiling.
Sound-deadening board has been used for decades and is also sold under many trade names. It is a soft, fibrous board 1/2” thick and quite light. Generally tan or dark brown and found at building material centers. This is not to be confused with compressed fiberglass.
Sound boards or panels are very light, and therefore don’t contribute because of any addition of mass like the previous solutions. In this case, the lightweight sponginess offers a slight amount of Absorption as well as minor Decoupling. Soundboard absorbs a little and decouples a little.
Adding insulation introduces the last element of the 4 Elements of Soundproofing: Damping. Damping converts the vibration energy into heat energy. This is a very efficient process with great soundproofing results. This is also the most common soundproofing solution for retrofitting walls assemblies, due to its low impact installation process. For very 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 wall. Because this method directly addresses the vibration, there will be much less sound available to travel to the joists and through the wall.