I have a semi-D with relatively good soundproofing between my side and the neighbours. The wall build-up is block-on-flat, sand and cement on both sides and then steel hat channel and drywall on both sides. Mostly the party wall provides adequate soundproofing. Conversations and telly are not heard, however, some sounds do get through, such as the neighbour's front door shutting and stairs. See pic of their front door. It is a structure borne noise and I know these are hard to reduce. Given this unwanted noise is actually not loud, is there any hope to reduce it? Assuming there are no gaps in the cement coat, I am wondering could the drywall cavity on both sides be creating a 'triple leaf effect'? One person advised me that removing the drywall and wet plaster or to use drywall with fibreglass attached that is not touching the block wall. Would this make a difference? The triple leaf effect is something a lot of guides don't mention.
The house is three floors and really like a slice of the cake, cut from a cake, the rest of the terrace, given how tall, wide but shallow this house is. I think this shape might worsen the noise pollution transfer the house is acting like one large speaker. Smaller the air gap, the more the higher frequencies can resonance right?
I am also looking into convincing the neighbours to install some kind of rubber cushion on their front door but I do not what product to use.