All light bars make noise; however, with the Ford/Rigid light bar, they specifically have a bracket that raises the light bar for soft tops that help reduce the whistle.
You can see the difference in the hardtop vs. soft top bracket in this thread...
Overlanding is awesome and you will love it. We just picked up our Bronco and are figuring out how much to incorporate into our overlanding setup. Just be cautious, the overlanding bug can be get out of control and consume you like it did us :D