When attempting to soundproof a room, there are various levels of sound isolation and many different types of materials available. How far you go with your construction will depend mostly on they type of sound you wish to abate. The acoustic solution needs to be designed around your specific application. Is it the noise of a neighboring industrial plastics shredder or do you need to isolate your studio control room?
A typical wall construction consists of two layers 1/2" gypsum applied to either side of a 2x4 wood or metal stud. Many of these walls for residential and commercial interiors will lack insulation in the cavities. This type of contruction will yeild an STC (Sound Transmission Loss) around 31 - 33. By simply adding a layer of fluffy glass fiber insulation to the cavity, the STC will increase by 4-5 points and prevent
sonic resonance. Additionally, a layer of mass loaded vinyl barrier will add another 4-5 points. We have prepared a simple video demonstration to illustrate how using multiple layers of common building materials will improve STC values. Click here for the video: http://www.acousticsfirst.com/educational-videos-the-barrier-and-the-bell.htm