I have a 50" Radius Bar from OKLEDLIGHTBARS and Relentless Fab mounts. As soon as I drove with the light bar, I notice that God awful whistle sound! So after researching I tried this. I used Edge Trim which can be found in any auto parts store and I put the Edge Trim on the bottom four slits of the heatsink. I eliminated the loud whistle.
Here is a video of some of the information and how to.