Plants of tree habit have the tendency to absorb and dissipate sound energy and hence act as buffer zone. Trees are planted along highways and other noisy places to mitigate the hazard of noise pollution. Certain trees are found very effective in reduction of noise pollution. Polyalthia longifolia of Annonaceae family is the best example of such type of tree species. The other suitable tree species are Azadirachta indica (Meliaceae), Tamarindus indicus (Fabaceae), Aegle marmelos (Rutaceae) etc.

what are criteria of selecting such plants?

Main criteria would be acoustic absorption : quantity of surface absorbants and reflectors (leaves/roots/bark, etc), thickness, granularity and thickness of surface texture. 

Evergreen variety may be a criteria as well as adaptation to the usage conditions.

Wind may also affect the result producing a good mask effect.