They like loud music, I snore. Help!

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I live on the first floor of a block of three one-bedroom flats (ground, first and second floors). There are no adjacent properties on any of the floors. As so often in modern buildings sound insulation is poor.

As the neighbour with whom I have the mutual difficulties is on the ground floor it would clearly make sense to add soundproofing to my floor. Is it also desirable/necessary to add further soundproofing to the walls in order to prevent so-called 'flanking' noise? Are there issues of sound conducting through the building frame? This would appear to be the case with the neighbour's stereo: I can't actually tell which room it is in.

The four walls of my bedroom are as follows: brick wall to shared stairwell; brick wall with window to side of block; plasterboard wall with door to my hallway; fitted cupboard and plasterboard wall with my living room.