So I think they should genetically engineer trees with branch and leaf fractal sizes such that they act as perfect frequency filters for the noise spectrum of traffic and plant them alongside roads, because that would be prettier than the walls that are used. Also genetically engineered grass with serrated edges and designed cilia so when the wind blows the grass sings in a deep, filling harmonic tone, like this: llllllllllllllllllllllllllllllllllllll.