Interesting point about sound insulation and Japanese roads. I find the Mk4 very quiet, and even flooring it is not really noisy, just the same kind of accel noise you'd get in a gearbox ICE taking it to high revs, and even then pretty muted. Perhaps just more noticeable because of the normal quietness.
I do find a difference in roads though, in electric mode and very noticeable in the E the quite "roar" of tyre noise is the sound you hear until you come to a section of road near here where brand new soft tarmac has been laid for a few hundred yards. Then there is almost an eerei silence, literally no noise at all, then the normal concrete mix starts again and the tyre noise coming back in is quite alarming because so very noticable after such "floating" silence. I wonder if that road ride in Japan is much better and the UK therefore needs special sound insulation?