the difference there is, the farmers were there first. so anyone moving into those places should have already known what they were getting into and if they didn't like it then don't move there. where do they think their food is going to come from if they put an end to farming? mining is not essential like farming.
Sound is nothing magical, put enough mass in front of it and it will stop, reflect enough of it and you won't hear it.
i don't know about that. you would need a very tall wall though because sound can be reflected up and over a wall.