RicodJour wrote:

Now we're finally getting somewhere. If you're looking to make it
quieter for the neighbors, you don't need to add mass - the block wall
already has a lot of mass. You're looking for an acoustical surface,
which is why I mentioned the Homasote panels. There are alternatives,
but that method is the best way to save your neighbors tender ears.

Which leads to another question - do you find that there is a problem
now with you hearing the neighbors activities?

Yes. The person next door lives alone, and I am only there sometimes doing
work when he is there. But, in some rooms, like the upstairs bathroom in
particular, it is almost like he is in the same room that I am in. People
who have been doing work there for me have said the same thing -- that you
can "hear everything" from next door.

The bathroom in particular is something I can fix somewhat, I think. Part
of the problem is the old recessed metal medicine cabinet. I took that out
and opened up the wall. I took out the goofy loose bricks in that area, and
I will be figuring out how to refill that space to cut down on the sound
transmission. In that one case, I have access to a fairly large hollow wall
area -- maybe 4 feet by 4 feet, above the ceramic wall tile -- it's a small
bathroom. I am not sure what will go in that space. Some people have said
to stuff fiber glass insulation in there. Maybe that will work -- I don't
know. I have also thought of using that spray foam stuff to fill most of
the void plus a few other techniques, but I am not sure.

But, my original post was about the rest of the party wall between the two
living rooms, bedrooms, etc.

If not, and assuming
that the construction on the other side of the partition wall is
similar (a good bet), you probably don't have to do anything. DadiOH
asked if the neighbors have complained, which, even if they haven't
would be a good thing to ask them - do you hear me knocking about
through the wall? Is there a problem with asking them?

R