When building the coop, use the idea used by airports. You will not be able to completely eliminate sound, so the idea is to reduce it by channeling it into a different direction. Use the ideas given to block the sound on the sides given above, but also use methods *like a chimney* to ventilate upwards so whatever sound escapes goes up instead of the sides *double glass windows to reduce sound*. I have seen places on airports use angled walls so sound is channeled up skyward. In the 1800s the more well to do city houses would fill their walls with rocks to minimize the noise from the road *I suspect this is one of the reasons brick and stone houses were preferred over wooden walls*. Just remember if you add rocks to the walls, you also add alot of weight, too.