Can't see the wood for the trees
Mad Jock
I'm not convinced, in fact I'm quite doubtful, that trees will do very much in terms of noise attenuation. They do absorb some sound, of course, compared to line of sight but you need something more "solid" like a barrier of some type. Oh and it needs to be tall otherwise low frequency noise will refract around it. My days in this field, no pun intended, a long time ago so I can't quote chapter and verse.
Of course, if you were to plant trees then a dense pine forest may help a tad. They do provide visual screening and since noise nuisance is highly subjective that may help.
Reminds me that about thirty years ago I was sent to measure noise levels at BZN at a site that was being looked at for residential development. IIRC it was right up next to the perimeter fence! In attendance was a rep from the property developers who wanted the go ahead and also a chap from the station who wanted more houses there like a hole in the head. Anyway, I wrote up the results and sent to them the MOD. What the outcome was I never found out.
BBK