Small trees and shrubs, like Cornus florida (flowering dogwood), Deutzia gracillis (slender deutzia), Ligustrum vulgare (common privet) and Taxus cuspidata (Japanese yew) will enclose the space, making it shadier and more private. I'd add an arbor or trellis, too, with Parthenocissus tricuspidata (Boston ivy) and a climbing rose like Lady Banks. For fragrance, nothing beats scented geraniums, or herbs likebasil, oregano, rosemary, sage, thyme and mint. A small waterfall or other water feature will mask noise from neighbors and traffic. Check out www.bhg.com for actual garden plans.