They have both over here in Aussie land, both a beeper and a "farter". The combination of both is a good idea. We all know the beeping sound indicates a reversing vehicle, and the white noise tells us which direction its coming from. Also fire trucks/ambos have rumblers, another gadget like the white noise beeper that tells you which direction the emergency vehicle is coming from.,(reply>), Have an edit for a nearly 12 month old reply. Our emergency vehicles now have white noise machines as well, along with lower frequency sirens that operate an octave or 2 below the usuall (bloody annoying) higher pitched one. Due to the fact the lower frequency one needs less volume to let people know, it is now quite common for them to only sound that one, to great effect. (get outta the way, I'm coming through, got a job to do / patient on board!)