i'm not really sure what a "sound wall" is exactly. but the mining operators like to spit out that phrase as though it's the solution to the noise problem when i'm not really sure how effective those things are. i guess each situation has to be evaluated on a case by case basis to see if the sound level is acceptable for people that live nearby. but to me, any noise at all that can still be heard decreases the quality of life of those residents and i am sure they feel the same way. unless you can eliminate 100% of the noise then it's still going to bother some people.
Fairly effective. Construction sites often erect a sound wall to reduce the noise, trains often have a sound wall to reduce the noise from train tracks, etc. Depending on the distances, it should reduce or eliminate the noise. It's kind of like a noise dampener. People do still live near airports or industrial areas so I don't think noise complaints is an entirely new issue.