We live in a Victorian flat conversion which occupies two floors. Our bedroom is directly above our living room and there is a chimney breast and (non-used) fireplace in both rooms. Recently we have had a new neighbour move in next door and his living room is next to our bedroom. He has a surround sound tv audio system and i think that he has the TV installed within the chimney breast for the fireplace on his side of the wall. The problem we have is that when he watches TV loudly the sound is coming through to our bedroom and living room through the chimney breast, not through the adjoining walls (from what i can gather). Any experts out there know how we can sound proof the chimney to get a good nights sleep?

Stuff a load of fibrous insulation roll up the chimney and see if that dampens the noise. There may only be a single skin of brick between your flue and his TV which is mounted on a metal bracket so the sound carries into the brick and out into the flue. Worse, he may have the sub woofer in the fireplace and it needs to be positioned on insulation to prevent the vibrations transmitting directly to you.

Talk directly to him and explain that it has always been a problem. This will prevent it becoming personal. Then try to test and see if the speaker positions can be moved to reduce the problem and if the tv itself is causing it.

If this doesn't work, you may need to line the party wall and chimney with acoustic plasterboard and acoustic lining system to provide adequate separation.

Thanks Jozeffo, that is really helpful.