We get many requests from clients to plant trees to reduce noise.
To get trees to reduce noise you need to plant a deep belt of trees (15 metres I read in one Austrian study).
The best way to reduce noise is either acoustic fencing ( https://www.jacksons-fencing.co.uk/acoustic-fencing.aspx ) or a soil bund (bank of soil).
Trees mainly only work in the mind to reduce noise, by screening; if you cannot see the source of the noise, it seems to be less of a noise.
It is also important to understand the noise can only really be addressed at two locations, close to the source or close to where you are (as it bounces around).
We often recommend that a noise consultant is used to provide expert advice, prior to any attempt to solve the problem. http://www.association-of-noise-consultants.co.uk/