Question

Source and listener moving perpendicular direction .why no doppler effect

Answer 1

Answer:

good morning is the best example

Answer 2

Doppler effect:

Doppler effect is defined as the change in frequency of sound received by the observer when there’s a relative change in distance between source and the observer. This effect can be prominent when the distance change is so much as to produce an observable change in sound.

In this case, the observer and source are moving in a perpendicular direction. There may be a change in distance between them. If the distance between them is not changing then the Doppler effect will not take place.