On this topic, are detached houses still better if they are built as close together as they can fit them? Normally now there is only the tiniest walk way between each such house, so its paying for a double wall separation vs a single one.
Yes. Sound just doesn't travel through walls, it travels along walls. By not having any walls joined to your neighbours you have no way for noise to travel that way. You decouple not just air noise, but flanking and impact noise as well.