"Phil L" wrote in message
...
BartC wrote:
What's astonishing is that the sound gets through 18" of breeze-block
wall, with or without a cavity. In fact in the loft I can hear next
door better than downstairs in my own house!

It would be astonishing if true, unfortunately it isn't, your party wall
is probably 4 inches, possibly 9 or 11, but there's not a cat in hells
chance it's 18.

I've now tried to put my hand over the top of it near the rafters, and
there's a space on the other side. I would need more tools (ie. a stick) to
know if that space is my neighbours loft, or the cavity.

But if it was a single skin, then where they made a big hole in it to put
the RSJ through for the loft conversion stuff, it would have come out the
other side!

So probably it's two skins of 4" wide breeze block, with an (as yet) unknown
cavity width. If the houses are symmetrical, then the gap would be 8"
(allowing for an inch of plaster each side).

Regarding the way the sound is transmitted, if I put my ear against it, I
can definitely seem to hear through the wall, rather than through my other
ear if the sound path was more circuitous. But I need to do more tests.
(Typical, the dogs aren't barking at the minute..)

--
Bartc