Put a wind deflector on, see If that will help with the wind noise. Had to make up some custom brackets as the Thule supplied brackets wouldn't fit OEM roof rack. :
How to Mount Thule Wind Fairing on OEM MK4 Roof Racks - YouTube
Thule Rack Fairings Review Video & Demo by ORS Racks Direct - YouTube
OEM Base Rail System (Roof Rack) and Thule Cargo Box + Thule Fairing - BMW 3-Series (E90 E92) Forum
Thule Evo Fixpoint WingBar Silver Complete Roof Rack - available at RackWarehouse.com
Thule fairing / wind deflector and universal roof rack, Car Accessories, Accessories on Carousell
What is the purpose of roof rack fairings?
Thule Fairing (52" X-Large) Wind deflector reduces noise and improves mileage at Crutchfield