Sound attenuation engineers will tell you noise suppression for fencing is difficult to achieve as the sound will just go over the top. I reckon your best bet is too build a twin skin fence. A bit like house framing where the support members are contained within the post line with sheeting [blue board or corrugated etc] to each side. In the resulting cavity, perhaps where privacy is needed the most, you can use noise suppresion insulation.
Talk to the neighbours they may want to contribute to a better standard of fence for the same reason.