I have a mature row of regular cedars that are about 14 ft tall. They get sun all day. I was wondering if I could plant a row of emerald cedars in front of these so we have less noise from the other side of the cedars that are there now. The sun would directly hit the new emerald cedars and the ones behind them would get sun on top still. Thanks!
A double row of cedars could survive satisfactorily if you plant them about 2 feet apart and alternate the trunks with the existing ones, in kind of a zig-zag pattern, i.e. each new trunk falling between the existing ones. The two feet between rows will also allow some sun to fall in the space between. It would be good to spread some compost in the whole area when you plant and then water thoroughly since so many trees will require nutrition and moisture. (Your existing cedars look quite healthy.) Emerald cedars will spread about 36-48″ wide.
This doesn’t guarantee an end to your noise problem, of course.