The first step is the full demolition of the walls and ceilings or cutting out the damaged plaster with an appropriate sharp knife. Make sure not to just cut out the exact area of the damaged plaster but give an extra 2 inches around it and in a squared shape as much as possible so that it is easier to hang the new blueboard. If insulation against the cold/hot weather is desired, the insulation is placed inside the walls at this point. This can also help to muffle sounds, but will not make the room sound proof.
Plaster walls and ceilings can get destroyed as a courtesy of a hurried plumber or electrician who does not care since they are not the ones patching the holes. Warning: Cutting through plaster is a messy job with the white dust and possible crumbling pieces. In a clean bucket with cool tap water, you will mix the plaster product, to the consistency of natural peanut butter. The plastering powder or mix to use will depend on the amount of time you need to get the finish done. You can get a basic idea reading this short list on the different types of plaster mixes.
Plastering work is certainly not an easy task but the end result is worth the effort and money invested. This is not a trade for an ordinary homeowner without experience who is trying to save money thus doing a DIY job. DIY in this case, we do not recommend. Fighting against time to get the correct texture on your walls or ceilings before the plaster dries is almost calamity, unless you are sure of what you are doing. Otherwise, you will end up having to call an expert to get it done right for you when you could have saved a lot of time and aggravation if you had called them to begin with.
Something to note: If you are looking for a more high-end finish, opt to have walls and ceiling done with a smooth finish. This finish is more desirable for aesthetic reasons and may make your house worth more. It also may cost a little more, but looks much better. It takes a true artisan with eyes for details to get your walls and ceilings finished in the appropriate manner.
To make a room sound proof, there are many steps to be accomplished. Besides having sound-proof, or close to sound-proof windows and doors, there are specific products that can be used to sound proof a room. After the framing is set up, either wood framing or steel framing, sound proof insulation is one product that can be used and it can reduce noise by approximately 70%. This certainly helps with noise reduction and would be the cheapest way to go about it. Besides reducing noise, let’s not forget that the insulation will help keep the room warmer in cold weather saving you money with heating and less hot in the Summer months saving you money in energy by not having your AC working so hard.
In addition, to make a room more sound-proof, there are sound proof boards that can be used/installed to make the room quieter. Also called Absorbing Acoustic Panels, they are much more costly than just regular blueboard/drywall. However, sure worth it depending on what you are trying to achieve.
QuietRock Sheetrock is a specialized product for sound proofing, which is known to reduce noise by about 80%, however, if the noise you are trying to block is impact noise (people walking for example), resilient channel and acoustic clip in addition to the QuietRock should be used. The material can be very costly. The work is certainly more laborious and heavy.