Change the speed of source and speed of observer and measure the apparent frequency received by observer.

A standing wave – also known as a stationary wave – is a wave that remains in a constant position.[br]It is the result of the interference of two waves of same amplitude, frequency and phase, going in opposite directions in the same medium.[br][br]There are some points of the medium that do not oscillate, called nodes.[br]There are some points of the medium that oscillate with maximum amplitude, called antinodes.