Earth Berm for noise control?
We live on a 1 acre plot, that, depending on the weather and wind direction, has what are maddening (to me)levels of traffic noise from the busy state highway that lies 1/2 mile west. (I know prevention is best. Unfortunately, the noise was slight, at worst, on the 7-8 trips I made to look at the house and evaluate noise)
The worst noise seems to come from the N and NW; I know plants are poor buffer against noise, and am considering an earth berm along the west and north property lines (abutting the street and forest preserve). To cast an effective noise shadow(for the front yard), the earth berm would probably be at least 10' high(due to the slope of the yard).
I'd cover it with foliage for aesthetics and erosion control, but I'm wondering if it's even practical. How wide a base would a sloped berm require? Is there any formula to calculate the base for a given height? Is this even going to be effective (not just psychologically- the road is already out of sight, but the grooved concrete and 50+ speeds make the noise obnoxious)?
Sorry this post is so long, but thanks for any help you can provide.
PS How effective would a 6foot solid privacy fence be for the back yard-any opinions?