Quote Originally Posted by Pharos View Post
"Sound vibrates the molecules in the wall the same as it des the molecules in the air - is my understanding anyway. So airborne and structure borne transmission are essentially the same thing. "

Yes Martin, but we are discussing which route the leakage may be through, and the curative treatment is appropriate to that route.
The curative treatment is the same either way - you need a very thick, very dense boundary between the source of the sound and the person you don't want to be hearing it! Or a vacuum. But that's even harder to achieve.

These modern apartment buildings have pretty thick concrete walls and floors between the flats though so I'm guessing that is working well in this particular situation. I had the same experience years ago living in an end terrace, saw the neighbour out front and asked her if the music was a bother, she said she had never heard me play any music. After that it was party time!