There are farms in suburban areas without sound walls??
Always thought this was a generally accepted requirement.
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.
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good sound walls are .................... ! ! !
two, three or four layers the sound is forced to angle up an away
or https://www.youtube.com/watch?v=0aGRhEmZaO8
I had 4 of these they sent the sound up they were 30 inches with 24 inch fans
this was good enough to not be loud
https://roofvents.com/retrofit-gravity-vents-aura-vent/av-30-rf-aura-vent-30-inch-diameter-retrofit/
if you added the fan they moved 3000cfm
if you got a 48 inch and added a fan they moved 7000 cfm
very quiet since much of the noise is muffled by the vents