The white noise instead of a beep will probably never be adopted in the US because it would cost money (regardless of how much safer it is). Maybe after a few thousand more people are crushed, and it costs companies more to pay out wrongful death settlements,(reply>), Except it costs nothing to just use a white noise instead of the beep for newer trucks, yet a brand new dump truck off the assembly line will probably have a standard beeper. So I highly doubt it comes down to money. It is likely more to do with regulations. Or just simply apathy.