I live in a 30s semi with neighbours that like to party. We're planning on putting soundproofing plasterboard in the alcoves (I think, open to better ideas), but the biggest source of noise is in my children's bedroom. The neighbours have their extractor fan in the chimney breast of their converted kitchen diner, and the noise travels right up. It sounds like they're in the room with you, singing karaoke.
What can we put in the chimney to block this particular source of noise? Is it worth boarding the exterior of the chimney breast too? We have the original fireplaces but they're purely decorative. Do we need to ventilate the chimney if we put something in it, and if so won't that just let all the noise through?