As of February 2020, I've never heard the white noise sound (in Illinois) and am not sure what my innate response would be. The long-familiar beep makes me instantly look around.<br>Just imagining, it seems to me simultaneous or alternating emission of <b>both</b> sounds might <b>really</b> grab one's attention, sort of the way flashing lights of different colors and timing on emergency vehicles does visually.,(reply>), Illinois is in USA,(reply>), @BlargSmarg - I specifically mentioned that I would refrain from making a judgment on it's efficacy, since I hadn't heard it in real life and was giving my thoughts on it from what I heard on the video, so I'm not certain where you get the idea idea that I was being critical of it.,(reply>), @Max Griswald Trust me, you can tell the difference. I've heard it quite a bit where I live and it's really not hard to tell the difference. In the video it sounds different then it does in real life and the frequent short bursts means you can definitely tell it's not an air break system. It's funny to see people being so very critical of it while also admitting that they have never heard it in person.,(reply>), @Daniel Newby - I haven't heard a vehicle equipped with the white noise backup sound, so I will refrain from making a judgment on it's efficacy, but I can assure you that I would definitely think that it meant "This large hunk of metal is stopping, don't worry about it".  The sound that is played in this video sounds very much like air being released from a brake system.  Releasing air from the system is how brakes are applied by commercial vehicles, which makes you think the vehicle is stopping, not moving.,(reply>), Your reaction will be to look directly at the thing that just made this loud ass hissing noise.  It pulls your attention directly to it instead of "looking around".  It's never been obvious to me that it meant the truck was backing up, but it was innately obvious that it meant "This large hung of metal is about to be moving, pay attention."