So I've been hearing this vibration rattle or buzzing noise... on rough roads and overpasses in southern California. I've uploaded a video clip. At 4 seconds I enter the overpass... and you can hear the buzzing noise from 6 seconds to 9 seconds, you might need to raise the volume.

Is this a normal noise from overpasses? My old cars didn't do this. Also I can't tell where it's coming from, maybe the rear upper area or who knows, could be the license plate for all I know.

Car is a 2015 IS 350 F Sport

 

I think I know what you're talking about.
Mine sounds like it's from the back, but I don't know where it is exactly.
I took it to the dealerships and they couldn't find anything either.