Light Bar Mount
#2
I would say for the most part they are mounted to a roof rack or a cross bar. If you want to spend money the proline4x4 mount is pretty nice. It is also fairly easy to make things yourself and mount them to the roof rails using L brackets and bolts.
#5
#8
The whistling is from the cheaper light bars cooling fin design on the back side of the bars..... Does not matter where you mount them. Now places on eBay sell little foam inserts to jam into the fins on the back of them to help reduce or eliminate the whistling. You can cut some strips of some sort of random foam and jam in between some of the fins as well which can greatly help reduce the noise. Worked for me on one before.
#9
Yes, the noise on the freeway is insane depending on the mount and lights you run. I have 4 smaller bars on my roof rack, granted I don't have the GOBI wind deflector installed because I don't care for the look but I can't have the sunroof open on the freeway and talk to my passenger it's so loud.
#10
Other than stuffing the fins on the back of the lower cost bars with foam or rubber blocks the other option is to go with crazily expensive top of the line light bars. They are a LOT more expensive but you can find plenty of reviews where there compare them side by side with the cheapo ones and the quality and light output are far better. That being said, I have not bought a $500+ light bar myself.... I cannot afford that for the little amount of use I'd actually get out of it.