We have a very old apartment, which the building itself is a heritage building. While the external walls are thick and solid, the internal walls are not very well sound proofed. We can easily hear neighbours noises, or another bedroom noises, or upstair footsteps. I have been doing researches on how to fix this and would like to hear some experienced people thoughts? Apparently there are two ways, one is to open out the existing walls and then replace or add the exisiting acoustic foams or some sort and then re plaster and paint the wall? Another way is to simply add another layer of plaster board to it? Has anyone done anything like this before? And if anyone has any recommendations to any traders that can help in inner Melbourne?