[aposm]

When I lived in Japan it was in a relatively recent (last 10 years) but not brand new apartment block - Maybe if you are talking about a rural area or an old postwar Showa era house, sure. But either way the sound proofing is worlds better than any new construction in the US.

[Tor3]

I'm in a 20 year old two-storey apartment right now (while we're building a new house), and the sound-proofing isn't non-existing but not as bad as some other apartments I'm aware of (where you can't make a sound without the neighbors start knocking on the walls/floors, and you're privy to thing you don't actually want to hear..) - but we can hear every footstep when the neighbors walk the stairs to their upper floor. The rooms which are more distant are fine, we don't actually hear them talking. Most of the time.