One day when the speed of sound in air is 343 m/s, a fire truck traveling at v, 31 m/s has a siren which produces a frequency of f = 422 Hz. Randomized Variables Vs=31 m/s f=422 Hz fa=1 What frequency, in units of hertz, does the driver of the truck hear? Hz One day when the speed of sound in air is 343 m/s, a fire truck traveling at v. = 31 m/s has a siren which produces a frequency of f = 422 Hz. Randomized Variables Vs=31 m/s f=422 Hz fa=1 What frequency, in units of hertz, does the driver of the truck hear? Hz