Apparent frequency calculation

Source, sound, observer are in same direction

f' = f	(	v-vo	)
		v-vs

if the direction of observer or source changes, then sign changes.

If freq. Appears be double the freq. of source, for a stationary observer, then

vs =	v
	2

If for a stationary observer freq. Appears to be half the real freq. Then

vs= -v