Should the beep-beep alert of a truck that is backing up increase in speed based on the speed the vehicle is going?

A garbage truck was backing down my street today to get to the people at the end of the cul-de-sac. Normally when they back the truck down, the reverse gear beeper sound is heard, at a normal cadence (beep-beep <wait 1 sec> beep-beep <wait 1 sec> and so on).

But sometimes the garbage truck is going slowly – maybe 1–2 mph, and sometimes more quickly on the straightaway (maybe 5 mph),

Should the beeps be faster as an indicator of the reverse speed being faster?